Jennys280Z

Hey guys, quick update here. Regarding the buzzing sound I heard from the back of my car, I didn't even think of this until FastWoman nailed it, but that buzzing sound I heard is almost surely some bolts I left loose (hand tight) on the back of the car (the ones that secure the end rubber pieces on the car). Since when I took the bumper off, I thought it was only the shock absorbers that couldn't be removed without dropping the fuel tank. GRRR I did gently move the AFM device while the engine was running. When I opened the flap (via the metal lever under the black cover) just a little bit for less than a second, the engine dipped and almost stalled. Then I slowly let it return to the position it wanted to stop at. It shakes around somewhat while the motor is running. I didn't want to push it the other way because I didn't want to break it. But if you guys think it's a good idea to lever it up rather than down (to cut off the air flow) I will do that as part of my troubleshooting later this week. Why would moving it the other way increase the engine speed? I'm really mad that a mechanic put headers on this car without coating/painting the iron. Now I have yucky rusty headers attached to my engine and what's to say that this automotive cancer won't spread to other parts of the engine or car? Also my oil pan is rusty and I'm debating how to de-rust it effectively. I bought some high temperature paint at Autozone, but other than hurting my fingers using sandpaper I don't know of a better way to get the rust off the pan carefully. Would you guys trust a NAPA brand thermostat for my car or should I get some other type or brand? The guy there tried to sell me one and a gasket. He says the part is good and that he has one on his truck, but what am I supposed to expect a NAPA salesman to say? Thanks again for helping me everyone. FastWoman is like my hero though. Sorry boys Fuel gauge and fitting shipped yesterday and are on the way yaaaay! I'll get some fuel hose and clamps along with a thermostat and gasket at NAPA if you guys think I can trust NAPA parts. But I *feel* better getting some kind of Japanese part, like a Tokico or whatnot.

Wow there's some good ideas I wouldn't have thought of. I don't have a cooking thermometer handy...yet. Since the thermostat is just labor intensive despite being no cost issue parts-wise I suppose it's worth some troubleshooting up front. I haven't ordered the tap and die set either yet so more tools and parts to come! A few of the above points I did address yesterday. I pulled the cover off the AFM, manipulated it gently to make sure it wasn't stuck, cleaned the potentiometer. Like last year, it seems impossible to unplug the connector underneath without taking the AFM pretty much all the way off. I can't even begin to see where that clip is or how I have to work it to unplug it. Here's the video I promised. It shows how badly the car is running if you listen carefully. Especially at 35 seconds, it runs badly like that no matter how much throttle is applied. I gave it a hard romp in 1st gear up to about 4000RPM yesterday and it was just as bad as it always is under any load/engine speed which would certainly rule out vacuum as my gauge so eloquently taught me. It's kinda hard to see the vacuum gauge in the video but it's sitting right on 13inHg before I revved. It took me a while here to figure out how to compress/upload the video myself but I did it! I forgot to mention last night, I heard another curious noise from the inside of the car I never heard before. It was a loud buzzing sound coming from the rear of the vehicle while I was sitting in it with the engine running at idle. I looked over my right shoulder (as if I was going to see something ) and the only thing I could think of is the fuel pump. So I got out real fast and ran around to the back and got real close to the fuel pump and saw/heard nothing unusual. By the time I got back in the car the sound went away. I am not sure this is the same sound I sometimes hear when I first turn the ignition on...it would have to be a much louder sound to hear it over the noise from the engine. But in any case, I've never heard a buzz like that with the engine on, and so because of this, I now add the fuel pump to the list of suspects of what's wrong with my car. Of course the fuel pressure test will be more important than ever when I get the gauge put in. I splurged and bought an Aeromotive 0-100 psi air-filled gauge for $30 along with the fitting that cozye suggested. Maybe you guys can help determine if the way the car sounds could point to a fuel problem. If I'm getting too little fuel plus too much air from vacuum issues that would certainly cause a lean mixture (and the lack of power and smoothness I'm experiencing). With the ignition testing I did yesterday on the plug wires and the fine shape I know my plugs to be in, I just don't have the heart to start pulling plugs today before the fuel pressure checks next weekend. http://www.youtube.com/watch?v=sKeyr6ICVcQ A huge new question I will be in anyone's debt who can answer...the Z has these semi-sphere rubber plugs in various places, like underneath my ignition coil, and as I noticed yesterday on my fuel pump. I've tugged on them before but don't want to pull too hard because I don't know how they come off. Maybe there's a trick to take them off right and I don't want to break anything. Or maybe they don't come off at all! But I would love to get under those round rubber caps and clean whatever connectors are under them if you guys could reassure me how to remove them that'd be awesome! PS It seems like the best way to find parts for these cars is to shop around (so it's not JUST for fun!) because every source seems to have the best price for something. ex. I paid $209 for a new master cylinder last year and I see Black Dragon has them for $100. But some of their other parts are very out of line compared to other sources. Take for instance their '75-76 $499 bumper shock absorbers! Ouch! So my potential purchase list so far (including recently): Fuel pressure gauge and fitting Fuel hose and clamps Thermostat and gaskets Tap and dies Thermometer Brake booster Anyhoo, my gut is telling me it's the fuel pump. Yes I know my manuals tell me that newbies always assume it's a fuel delivery problem and ignore ignition but I haven't ignored ignition and tried to focus on that first... xx

Thanks for the help! I love you guys! I love everyone who drives a Datsun even if they think I'm annoying ...well...A few of the things y'all mentioned here might be beyond me but I'll do more homework online and offline when I have time. Right now I'm so bummed I don't even want to think about my car after I type this! A short update: I took the car for a ride. It ran badly as expected. Like a constant miss. Brrrrr-brrrrr-brrrrr-brrrrr-brrrrr and when I applied throttle it keeps doing it but more like brrr-brrr-brrr-brrr-brrr-brrr . I tried to take some video but I don't know how it turned out. My camera ran out of memory really fast because I left it full of pics so...but...I'll try to get it on the PC and upload it and link it here later. *sigh* Okay... A few months ago I replaced all the spark plug wires with new NGK wires. NGK spark plugs are all in great shape with less than 1000 miles on them. Dist looks great. Fuel pressure is still unknown because I just ordered the gauge and fitting last night. It is expected to ship Monday and I should have it before next weekend I hope. I'll post the results then. But do I have to disconnect the wire at the fuel pump and the starter and the negative battery cable and all this stuff just to take a fuel hose off and install a fuel filter or a gauge??? Gawd what for??? I spent a long time with the timing light today and I began to feel like we were one and I became entranced by the flashing lights. My timing is indeed right at 10degBTDC and seemed to stay pegged right there regardless of how long the engine idled/warmed. The RPMs were up in the 900s right after I started the motor up and then it gradually came down into the 800s. I spent a good minute or two on every spark plug wire with the timing light. There's a good strobe with every wire. No missing flashes at all that I could tell. Intake manifold vacuum fluctuates between 13-14 in.Hg at 1145 ft above sea level at 800 RPM. I played with the accelerator pedal while the gauge was hooked up at the brake booster connector at the intake manifold per Atlantic Z and also because I had that taped shut anyway since my brake booster is shot. When I hit the gas the vacuum shot down to 5 in Hg quickly and then read as follows: 15-16 in. Hg at 1200 RPM. 18"Hg at 1600 RPM. I noticed while I was dialing in the idle speed screw, I would hear a hissing noise that seemed to come and go. I would turn down the idle a quarter turn and I would hear it, then turn the idle down s'more and it'd go away. Make another quarter turn and I'd hear it again...and so forth. As the motor warmed up I was able to get a fairly stable idle between 790 and 820RPM, with an occasional run up to 830 or 840 which would only last a second or two. I had no idea there was an HVAC line that could be leaking vacuum connecting to the intake manifold. I don't know where this connects at. I'll do more homework about this later. There's a tinny-metallic rattling-vibrating noise that might be getting more severe that sounds like it's coming somewhere either under my dash or through the floor where the transmission is. I've heard this sound before now though it was a bit more pronounced today. Trannys and clutches are definitely beyond me so I don't want to discuss working on those , just mentioning the sound for diagnostic reasons. heh Temperature gauge never went past 135 degrees today in about 55 degF outside temp. I cleaned the temp sensor and the thermotime electrical connectors earlier this year with some Deoxit. My oil pressure always notoriously read low until I cleaned that sensor near the oil filter and now my gauge reads higher than ever (it actually moves off the zero when I apply some light throttle ). Cleaning the temp sensor seems to have had the opposite effect on my temp gauge! j/k it's probably the thermostat. I see that black dragon has them (had?) for about $10 and the two little gaskets are a few bucks apiece. I might order a new parking brake boot, throttle boot (mine is falling apart), and I wish what I really need more than anything, a LOCKING GAS CAP, but alas they don't have any for a '76 model, and I can't find one for sale anywhere (I used to have one too! *cries*). I have an aftermarket air conditioning on this car but it isn't charged up and I doubt it would work anyway. Earlier this year I took the A/C belt off the compressor pulley and then tightened the alternator belt which was very loose. It's tight now the way it should be though the belt is old and I can see it slipping a little when I'm using the timing light. I'm mentioning that I removed this belt because I never even thought that vacuum issues might relate to the heater/AC. In one of my old threads my car was running so awesome too! rmember? But GRRRR that didn't last long! It's so frustrating when nothing happens to my car but it sits in the garage, and then the next time I start it, it's horrible again from out of nowhere! Really down and out right now so I'm going to grab a bite out and then maybe post that video later or tomorrow if it sounds/looks informative. I have downloaded and printed the EFI Bible which is for a '75 280Z and I ran all the relevant tests from the ECU which I posted on the board. Everything seemed okay...the resistances for the AFM looked high, but then my car magically fixed itself for a while, which is why I mentioned I don't think the AFM can fix itself and then break again. I guess the thing I could have done today but didn't is to start pulling spark plug wires and checking for differences. I'm kindof scared to do that. I guess I can do it tomorrow tho. *shrugs* I don't want to get gasoline in my oil again for nothing but what can a girl do??? When I pull a spark plug wire off (at the plug) and then start the car to check for a difference in how it runs, does the plug wire need to be grounded near some metal or can it just be sitting anywhere? I guess the two questions in bold are the most critical ones that are giving me the most amount of headache not knowing the answers. I need to eat dinner... going out and getting drunk too Peace! xx

*grumbles* Well I think I spoke too soon! It seems that just idling the car wasn't enough of a test. Though I can verify that all cylinders are getting spark and that's not the problem, the car's RPMs dropped abnormally as soon as I put it in reverse and released the clutch. When it's running normally I don't even have to blip the gas. Just put it in reverse, gently release the clutch and the RPMs drop a little I guess but it pulls right out of the garage with no gas necessary. As it's running now the RPMs dipped down to like 400-500 and it might have even stalled if I didn't tap the gas a few times to get it rolling. First gear was the same as I lined it up in the driveway the RPMs dipped, the chug-chug became more noticeable. I guess when the engine is loaded with the car and it's not in neutral the problem is more severe than in idle (eliminating vacuum leak as the problem I would guess). So if ignition and vacuum are ruled out, what else? It doesn't backfire but the idle speed in neutral spikes between anywhere between 770 and 860RPM the way I left it. Timing seemed good before (right on 10BTDC) but I'm going to check it again today because I might have misread what the little points on the plate mean. I took a photo, labeled it, and will post it here for posterity. There aren't enough photos of this kind of stuff on the internet as it is. I'm also including a photo of where my distributor body's timing is set just in case it looks unusual to anyone. I'm guessing that turning it counterclockwise advances the timing? So the problem seems constant, most noticeable in gear, no black smoke (or any smoke), slight smell of gas (normal), no power and a rough running/idling engine. The blub-blub-blub in neutral sounded great but when I drove it....it blub blubbed with no power down the street too! All the vacuum hoses mentioned above have been replaced and so that's all in better shape than ever. The car was running fantastic and literally the next one or two times I started it up, it's right back to this again! Does timing go out all of a sudden like this? Does an AFM break, then work, then break again? The motor starts very easily. It fires right up in a fraction of a second every time. It just doesn't want to run right! I'm going to buy the fuel pressure gauge and fitting linked to above, get a new section of hose and four clamps, cut it to fit and then it'll be optional whether I decide to use it permanently or not. Someone on the board once mentioned that there's a filter in the nose of the fuel pump that can get clogged. Can I inspect/remove that filter in the fuel pump without removing the fuel pump? The fuel pump on there now, while it sat in storage for a long time, hasn't seen very many miles. The ignition coil...I have read that they either work or they don't and that one shouldn't expect that it's delivering "weak" spark. My car still reads too cool on the temp gauge. It's slow to get off of 120 and slowly rises to about ~140 and sits there. Doubt this is related to how the engine runs. Any advice on "next place to look" would be awesome! Thank you. Check the photos out too! xx Oh yeah, the craziest thing of all when you look at this photo? Just randomly shutting the motor off, the timing notch on the crank pulley stopped exactly on the zero timing mark. I could try to duplicate that again a hundred more times and would never be able to do it twice. It's just one of those crazy things I guess. Oh and disregard that chalk mark on the 15deg line. I just drew that on there to make sure that what I was looking at was happening north of that line...back when I thought that reading the timing would still be really hard even with the chalk marks on it. I'm going to remove that line and draw one at around 13deg and another one at 7deg and hope I'm somewhere between the two lines. I questioned disconnecting the temp sensor wire and grounding it like my 70-79 shop manual recommended. But my FSM from Tokyo said nothing of the sort. It just says timing is retarded when the engine is warmed up. 7degBTDC, setting advanced timing not required unless setting phase diff. How do mechanics dial in the timing accurately when the idle speed varies and the motor doesn't seem to warm up?

Hey you! You were right!!! I didn't want to post again until I had an update. I didn't know how things would be going because I went through 6 auto parts dealers here until I found one with some 3/16" hose in stock! (5 ft of continuous hose at least). I couldn't believe that the first place I drove to was out, so I went home and called five more places before they had some? I mean what is the deal? That's like a lawyer's office with no printer ink! I couldn't post an update because I didn't have anything connected to the dist or the throttle body and my little 3-way connector was off the car so I finally got it put on yesterday. So those vacuum lines were also shot and I had to replace those too at the same time. But I wanted to use my timing light and this time actually check the timing for the first time ever! So after lots of squinting and bending and using my little mirror and taking a dozen pictures of the pulley from underneath the car, I couldn't see or feel any timing mark on the pulley. So I blipped the car to turnover for a fraction of a second to move the pulley and then took a dozen more pictures and finally that mark showed up in one of them. After I was able to mark it with chalk, seeing the timing was so easy! I thought it was still going to be difficult but it's amazing how chalk takes it from impossible to a cinch. My FSM says when the motor is warm the timing is retarded and it's unnecessary to check it while advanced unless I'm adjusting the phase difference thingie. My car started on the third "blip" of the key by accident that's how badly it wanted to run I guess! And you were right! It felt a lot better. First I noticed it was idling at a normal speed, then I made sure all my spark plugs were firing, then I noticed my RPM continued to slowly increase the longer the motor idled and I had to keep dialing the idle speed down (maybe as the engine warmed up?) to keep it at 800RPM. Then I shut the motor off since it started accidentally, found that mark, chalked it, and started it again and checked timing. It was sparking right at 10deg BTDC, vacuum advance hose on the dist and no temperature wires disconnected/grounded. Of course my car didn't warm up all the way before I did this (at least the gauge didn't). It was sitting at about 145F and didn't want to go much higher. But it seemed to be running great! The throttle was responsive, it revved normally, no backfires or stumbles, idled pretty smoothly, started so fast it started on accident, and so a little road test in the next day or two will be the final test that it's running great for sure! Thank you for the advice on the tap and die. I will get one of those. I have the antiseize compound already that I've used for my spark plugs and alternator so far. But before I worry about my thermostat I really want to fix my brake booster so the car will be fully driveable again (well actually I am getting my seats reupholstered somewhere soon and took my passenger seat out for now and so my car looks like a race car now! Rooooom! But soon my driver's seat too which is in worse shape on the seat) But it's scary to drive with the brakes so weak and so I really don't want to drive it but for short distances and in the daytime. I looked under my dash at how my brake booster was connected to the brake pedal and it was a little confusing. I saw one bolt there that I could loosen so I guess I can just get to loosening that and see what happens! Thank you so much for your help again! You helped me a lot in the past too and I should thank you for being so helpful to me. I love this website! I need to spend a lot of time here reading through threads. I've learned more from this website than from my manual already and I haven't even cracked the surface of what's on here yet!

Yup! You're right Zed Head it's a flame arrestor! I was really feeling guilty about putting it back in there before installing it until now. Here's a link to more information and a photo of what I saw through the hose, though the info. in the responses here is not exactly error-free. But I'll leave it to you guys to parse out the good info. from the bad. http://www.zcar.com/70-83_tech_discussion_forum/spark_arrestor_where_is_it_whats_it_look_866736.0.html One thing I read on this link that I didn't know is to only use fuel-injection hose on the intake manifold and not heater hose. I don't think that applies to this hose as it's not connected to the intake manifold. Anyway the hose I used is a heater hose; seems to me like it would be more than sufficient to the task of PCV return but you know me, I dunno...:stupid:

Here's a drawing of what I'm talking about. It was sitting in my rocker cover PCV hose. What is this thing?

Hiya guys!!! Yep there was a big crack in that hose, probably caused from the old-style clamps being tightened and digging into the hose putting a knife-like slice right through it. So I took off that rocker cover hose, and measured it as a 17mm (probably 16mm) (and approximately 23.5cm or 9.25" long) but the closest thing the auto parts store had was a 5/8" which I thought might be a problem but it wasn't and installed easily. But when I held the old hose up to the window and looked through it I was amazed at what I saw! Have you guys watched those old westerns where a tumbleweed blows down the street right before a gunfight? Well that's what was inside my hose! I thought it might be a natural formation of oil/dust that crystallized like that over the years. But what I extracted was very much man-made. It's a wire ball with hooks on either side. So my question is now, what is this thing, where did it come from, and what should I do with it? It was near the middle of the hose before I pulled it out. Not fastened to anything despite the hooks, but the friction against the inner walls of the hose is more than strong enough that it wasn't bound to move anywhere. Should I install the new hose with this thing in there? Maybe it serves as a kind of stopper to prevent large pieces of dirt or sludge from blowing into the throttle body? *shrugs* Does anyone get rid of their carbon canister? I don't have emissions tests here anymore even if I was registered to drive but because there's also a venting line coming from the fuel tank I'm leery about bypassing it or removing it. But it'd be nice if I could just run just one vacuum line from the distributor to the throttle body and that's all. cozye, about what you said about water temp sensors, I actually have noticed that my temperature gauge does not seem to warm up like it should. I remember when my engine was fully warmed up in the past, the needle would sit about half way, maybe a little higher than half-way to about 185-190 degrees. But now even after running the motor for 20 minutes it doesn't even rise a third of the way up, so it reads about 25-30 degrees low. I wondered if this was a faulty thermostat stuck in the open position but now that you brought this up, could this also be related to my problem? I've read some articles online in the past talking about adding that resistor to the circuit too now that you mention it. Thanks! I've decided to eventually test fuel pressure above the fuel filter where a new hose exists I already put on a year or so ago. It's easier to see what I'm doing above the filter than below it, and the hose below it isn't as horizontal as I thought either. Also, I'm going to test the fuel pressure with the engine running and through a T-connector, per recommendation of one of the local Z mechanics. I will buy this one; it should pretty much pay for itself after just one use, as it would cost almost as much in labor to get a mechanic to do it for me. I hope this one will work for me: http://www.amazon.com/Actron-CP7838-Professional-Pressure-Tester/dp/B0009XQUKC/ref=sr_1_1?ie=UTF8&s=automotive&qid=1290148880&sr=8-1

Well my car was running great and almost all at once in between times I drove it, the next time I turned the key it seemed to be back to where it was before -- running poorly as if it wasn't firing on all cylinders. If you guys remember I caught my #1 cylinder not firing and just cleaning the contacts on either end of the #1 spark plug wire, cleaning and gapping the plug and the car ran wonderfully again. For a few more drives at least. Then it was right back to running terribly again. But even worse, it was running badly and I verified that all six plugs were firing with my timing light so whatever was affecting it this time wasn't as simple as a dead cylinder. In case of poor spark, I've replaced all my spark plug wires with the same blue NGK brand, looked over my NGK V-Power plugs again and verified they were all in normal and great condition, looked over the distributor again and verified it was clean and in great shape. And I ran into this story: http://mybuildgarage.com/2010/09/1975-datsun-280z-restoration/ If you read just below where it says: "Looks like this issue was a two parter!" it sounds like his car is suffering the same problem mine is. I emailed him last week on youtube but no response so far. It's crazy how he starts describing the problem and not mentioning how he fixed it! He goes right into talking about polishing his wheels and taking the car on long trips, so I know he fixed the problem somehow. My car at one point was misfiring and popping too, sounding like from the intake, until I added brand new gas, and then the backfiring went away but it still ran horribly. But I wonder now if this had to do with the fact that I let it sit and started it up again (intermittent) than the fact that I changed the gas. It seems like just letting it sit and starting it up again a few days later is all it took to go from great to terrible again. I don't think AFMs break and then magically fix themselves, maybe this is how they go bad though. So I think this is an ignition problem even though the car doesn't seem to want to rev to high RPMS in neutral or while driving, and there is no power to where it feels like I'm driving a golf cart instead of a Z. I'm too scared to go full throttle to see if there's a difference in that vs. light/medium throttle so maybe one of you guys can come drive my car? j/k If you guys remember my car has no vacuum switching valve. It was removed and bypassed So before I write another novel, and to continue on from a previous post here months ago, I have found the vacuum line to the distributor was cracked. I got some electric tape and taped it back on for a short term fix but it turns out it's virtually severed in two. So I ordered some new 5mm silicone vacuum hose on Ebay and hopefully it shipped today. I'm wondering since my car was set up for full-time vacuum advance but I wasn't getting hardly any vaccum to the distributor because my hose was cracked, if this could retard my timing sufficiently to make my car run like hell, even at light to moderate throttle? Or without this vacuum present, could this somehow cause an intermittent problem with the distributor firing the spark plugs, particularly with the #1 cylinder...? Another really stupid question someone will get mad at me for asking, but what is the hose that goes from the rocker cover to the throttle body for exactly? I guess that this just reroutes air caught above the camshaft back to the engine to be recycled and burned. But if this hose is cracked really bad, will this disturb the vacuum in the system even more? And my brake booster is still kaput. So I disconnected the hose to it at the intake manifold and taped the pipe shut. (Yes I drove with unboosted brakes yaay) I figured if I left it open it would be a huge vacuum leak but since I've taped it shut that should have completely stopped the leak there. BUT...couldn't that magnify or exaggerate the vacuum leaks elsewhere in the system like these cracked/taped hoses I'm talking about? Can I get my brake booster off without disconnecting my master cylinder from the brake lines (and thereby not make a mess, not get air in the lines and add a lot more work?). I have three manuals here and no good step-by-step for removing the brake booster. I would assume I have to drain the master cylinder, separate the brake lines from it, disconnect the brake pedal from the linkage to the master vac, disconnect the master cylinder from the master vac, unbolt the master vac from the firewall via four bolts underneath the dash, and reinstall another one with the reverse of this procedure. Is this correct? Is there anything else I need to know, or any helpful hints that could help me get the job done? Thanks! Also, using the timing light to check my dist timing is so hard. It flashes so fast, and honestly I can't even see the little notch on my crank pulley at all when it goes by. So I scored some chalk the other day. I'm going to stick my nose in there and try to find that notch and chalk it up, and then put some chalk marks on the timing plate on the front cover around the 13 degree line, and THEN see if I can use my bionic vision to see the chalk lines meet up there even though it's flashing like three times too fast! GRRRRR It's hard to do this on my own especially when I have no experience or anyone mechanically inclined among friends or family that I won't have to tow my car and spend money on to help me. I cleaned the electrical contact on my TPS. It was the last contact in the EFI system I didn't clean, sans the fuel injectors themselves which is the only thing I haven't cleaned. I doubt that has anything to do with my problem but here's to being complete. I checked my manifold vacuum on the same day I found my #1 plug not firing. It was fairly constant at about 13 in Hg +/- 0.5 in. when I want about 17-18 in. here at 4000ft above sea level. I haven't bought a fuel pressure gauge yet but this is something I've been meaning to do. I am wondering where the best (easiest, while being informative) place to check pressure is? I'm thinking at the rubber hose right above the fuel filter. Should I use a T-connector and let fuel go to the injectors or can I just plug the gauge right into the hose from the fuel filter and stop the flow to the engine? This is an electrical fuel pump so I assume I don't have to start the motor to check the fuel pressure but just turn the ignition on, right? I haven't done this yet because I've been told that fuel doesn't keep an engine from revving, only air can do that. (Not sure this is true). Sorry for so many issues. Even my issues have issues but you guys have been helpful to me here.

I'm having the exact same issue and I see from this thread that it's the brake booster. :paranoid: I seem to have rust on the surface of my brake booster too...where my brand new master cylinder is bolted on. Uggh how messy is this going to be? I raised my idle to about 900 RPM in the hopes that the extra 100 RPM will keep the motor from dying when I'm on the brakes. I feel a very smooth vibration in the brake pedal when pressing it, hear the same whooshing sound, and my RPM drops 150-200 when I press the brakes. I haven't let the car warm up all the way to see if the problem becomes less noticeable. I was testing my intake manifold vacuum through the hose that goes to the check valve/booster and this problem occurred soon after doing that. I was wondering if a little bit of twist I was putting on the valve on the other end of the hose I was twisting to remove might have upset it but this is probably wishful thinking at this point

Awww I'm so happy to hear that grantf! I learned a lot too! There's an old saying "necessity is the mother of invention" and even though I didn't invent anything, the need I felt to fix my Z made me read my manuals slowly and repeatedly until I actually understood them! And that's a great point, to start with the simple things first. Honestly though, I was still figuring out what the simple things were and thanks!

Hi Zed Head! I'm sorry I was away for so long. Where did the month go? Ugggh! Yep my Z's still running really good! The AFM is fine as I suspected then that it might be. Or at the very least, I was never ready to concede that it was defective. And it's not, despite those readings. Sure they were high, but apparently not too high. Actually when you told me you had the exact same readings, it encouraged me that my AFM might NOT be defective rather than the reverse. I was going to keep it to the bitter end in any case, and the decision worked out for me. Your help was sooo appreciated, thanks again! And gosh, how lucky was I that cylinder one was dead? I wouldn't have even thought of checking the other cylinders with my timing light and I admit I really lucked out on my diagnosis there! P.S. The resistance readings in the EFI Bible were for 1975, and I have a 1976. Not sure this would make any difference but I never know.

So the dead cylinder explains all the symptoms I experienced, why my fuel gauge went down so fast yet didn't blow any black smoke from rich condition (just the uncombusted gasoline fouling the oil through the rings plus mostly just shooting out the tailpipe!) Yup, I changed the oil before driving it any more than that one time. Treated the dirty parts of the engine (front cover and oil pan) to a foaming degreaser too! Now it's so clean I can eat off of it again! Yay!

The problem was the plug or else the plug wire. Immediately my baby fired up and idled up to 1000+RPMs in that sweet silky smoothness I remember! Then settled back to 800 after a minute of warming up. I tapped the gas pedal a few times and I was so happy it wasn't chug-a-chug-a anymore! That was a fun drive; running better than ever maybe!!! :love: Thanks everyone for all your help! :kiss: I'm going to have waking dreams about my car before bed tonight!!!

My #1 Cylinder is dead! That would explain, I am presuming, all of the symptoms I've been having lately with my car, namely: 1. Low, rough idle 2. No power; runs rough at all throttles 3. Was misfiring badly before I changed the year-old gasoline in it. As soon as I ran the fresh gas through it, the misfires stopped immediately but it still ran crappy. Well maybe the misfires are still there but are very faint and not *popping* loudly like before. But what about 4. Car won't (seem to) heat up to normal temperatures (doesn't reach ~140deg)??? The temperature switch/sensors are right at the front of the engine, right in front of cylinder #1. If that cylinder is not firing, could this cause a too-low reading at the temp gauge (even though the gauge is reading "coolant temp"?) I know it's not firing because I bought a timing light, hooked it up, and it gave no readings. I didn't know if I had a faulty light, hooked it up wrong, or had a dead cylinder. So I hooked it up to cylinder #2 and everything with the timing light worked as it should. But I can't check nor set timing with a dead #1 cylinder. So what could be wrong? I checked the spark plug wire. I cleaned both ends with contact cleaner. I pulled the spark plug and inspected it. It was wet with gas (good sign! and to be expected). It was carbon fouled, so I lightly sanded it with 400 grit and cleaned some of the carbon off so it is more of a brown color now instead of black. The gap is fine and the plug otherwise looks in great shape. It is an NGK V-POWER. I'm going to start it again and see if there's any difference but I don't suspect there will be. I made sure both ends of the wire are plugged in correctly. There are no visible cracks in the wire, and the connectors (ends) of the wire looked pristine even before I cleaned them. I hope that there isn't something mechanically wrong with my cylinder (compression?) Maybe some experienced folks here know what a dead #1 cylinder might usually mean? Like maybe Zs lose their #1 cylinder more often than others and it is best to check the *blank* first? It can't be the coil or the line to the distributor because the other cylinders work fine. I guess it could be the distributor...maybe something wrong with where the rotor points at #1's position? Thanks! Jen

Hi Zed Head, welp I still haven't started it yet! Thus far I've cleaned the water temp connector, Thermotime, fusible links, firewall ground, EFI power connectors, oil pressure sensor, AFM potentiator contacts, EFI bullets, air regulator, cold start valve, voltage regulator, AFM ground, ECU, ballast, battery, alternator, fuse box, etc. I couldn't budge the EFI ground (near the air regulator) with wrench or screwdriver. Despite no rust it seems to be stuck like glue. Wonder if a few days of WD-40 on it made any diff. The ECU is back in. Doing what I could with the AFM still installed didn't affect the resistance readings at all. In fact the 199 Ohm reading changed to 214 for whatever reason. I cleaned the contacts one more time including at the ECU connector, and hooked it back up. I'm charging the battery right now. It was 11.74 volts last night and 11.71 volts today. I observed some cracks in the big vacuum hose going to the rocker cover (in pics) on careful inspection I never saw before and am wondering how much these will effect how the car runs. I'm going to try to tape them with electrical tape after I start the car and see if there is any observable effect in the car's idle at all. On a lighter note, I got the seized bolt on my alternator freed and adjusted the belt's tightness just right! Looking at my repair records this must be the original alternator and I'm real impressed at its longevity. Last Thursday was the first decent weather we've had (low 40s, low chance of precip) and it was basically ready to start, but the overcast skies looked ominous and I don't want to get stuck in the rain for a variety of reasons. A big one is because I have the infamous leak to the floorpan on the driver's side. Another is because the car is largely rust-free but that doesn't mean I'm not at war on rust and will thusly keep the car dry at all times. :laugh: I put the horns back on. Still only the LH horn works. The connector on the RH felt loose so hoping that a pinch with some pliers will fix it. I included a picture of the connector on my TPS too, not because it's having trouble just because of the cracks on it. It is representative of other similar connectors under the hood all showing the same cracked wear. The conn on my air regulator was cracked all the way through.

Oh I didn't see any adjustment on the top of my Deoxit can, I'll go check it out. (edit: Wow that's cool! It's on low now and 1000% better!) The EFI Bible said I should get continuity in that ECU-AR-FP circuit. Could 64 or 68 Ohms be regarded as continuity, perhaps when compared relative to some much larger number in the thousands of Ohms or something? I'm going to go look at my FSM again now too. Thanks Zed Head!! PS my Z did idle too low when I ran it the last few times, and it was cold out. *shrugs*

Update for the general board members: I cleaned the potentiometer, let the cleaner dry, fully charged the battery, and still have the exact same resistance readings (226, 199, 125 Ohms on Bible tests 1-3a to 1-3c). Thank you for that link, TomoHawk! I surfed to that article a few weeks ago but never found it again so now I have it bookmarked! I think it's the case that I simply can't see the wiper from the angle I'm looking at my Pot from (I didn't take the front cover all the way off, it's still "stuck" along the bottom edge). If you look at the first big photo in the "AFM adjustment" section of the atlanticz article, you can barely see the wiper and that's pretty close to the angle I'm seeing it. Actually my angle is even worse so I can see how I missed it now. So I'm going to go back and delete incorrect info. that I wrote above. :stupid: I love that smiley! That's definitely me sometimes. The guide explains well that it's best to be certain many other EFI parts be operating and adjusted correctly before tampering at all with the AFM or then you'll be in the unenviable position of having two (or more) parts out of whack at the same time! All in a day's work of 'Making A Mess'. So I'm not going to unscrew anything or try to adjust anything on the potentiometer. I noticed that when I tried to gently rotate the wiper counterclockwise (with my thumb on the counterweight), it seemed stuck and wouldn't move. I was gentle though. Does the car need to be running for this to move freely? It moved about 1/2cm clockwise and then stopped. (Edit: Sorry and nevermind, it moved CCW okay, I was just too gentle with it) Interestingly, that atlanticz guide is suggesting there is resistance (of variable nature) across pins 7 and 8 depending on flap position. With the car off, and the flap closed (I presume), should that really be "continuity"? Not sure why I'm getting 199 Ohms for something that's wanting continuity. Is continuity always defined as something extremely low (0-2 Ohms for instance) or is it all relative? Sorry not asking anyone in particular all this stuff, just putting it out there for general discussion. Thanks all, for this wonderful resource!!! I hope everyone has a great weekend!

So that's what the 5 meant. I want some 100 too grrrrr

sorry for the mixup. I must've been drunk.

Update on where I am now. 1. I fully charged the battery. Well I thought I did. It measured 12.59V when I took the charger leads off. A minute later after removing the charger leads it was already 12.35V. After I ran several more circuit tests from the ECU I measured it again at 11.99V. Was that from just leaving the door open and the dome light on and running tests? It looks to me like this battery is not holding a charge (Energizer brand). And it's been somewhat abused through the first almost two years of its life (drained, charged, drained, charged, and when not charged by a charger it was likely never fully charged by the alternator). 2. I retested the AFM for absolutely no change in the readings above. 226, 200, and 125.9 Ohms respectively. However charging the battery did possibly have an effect on the ECU-air regulator-fuel pump circuit as it lowered from 68.7 Ohms to 64.5 Ohms. Last night I inspected, removed and cleaned the electrical connector to the air regulator. There were lots of cracks in the black rubber plug (insulator) behind the plastic box of the connector, well not really cracks but holes that go all the way through it. I tried to fit/tighten it into shape by hand when I reconnected it, and wanted to use a piece of electric tape to hold it there but it was still wet from the Deoxit and the tape didn't stick so I took it off. I'll test it again tonight to see if there's even more improvement in the 64 Ohm reading. Cleaning connectors at the fuel pump might be another option to improve the continuity though I can't remember what they look like back there. My car is so low not even I can get under there to look without jacking it up...well at least not on my creeper. Maybe if I got flat on my back on the floor...ewwww Anyhoo I spent about an hour with a tiny screwdriver scraping most of that sealer off my AFM front cover last night. I didn't expect to get it off last night but I got an idea courtesy of my engineering prowess. Looking at the shape of the AFM housing, one can use its inherent design to manipulate a lever to apply evenly distributed force across the entire top rim of the front cover. Without an intermediary surface, a large screwdriver would only contact the lip at a non-normal angle (approx. 45deg) and this is inadequate as one is applying almost as much force up as one is out (the cosine of the angle). We want to take the cover straight out as I discovered above thanks to Zed Head. Sooooo, I used my folding straightedge, three ruler widths deep across, spanning the upper surface of my AFM housing, and used the slot screwdriver to lever off the cover with force at a nearly normal angle (90deg)with one hand while pressing the rulers down flush on the AFM housing with my other. It applied even force across the entire upper surface of the front cover's rim and didn't take long to hear that satisfying unsticking sound, that the sealer had given up its fight. That was all the time I had last night. Haven't cleaned it yet. Just left the cover mostly closed around the bottom of it and put a plastic bag around it to keep it as surgery as possible. I did open the door and look inside. I almost freaked that I could NOT see the wiper inside and my first impulse was almost to start screaming that Tom took my wiper out. I think this is due to my viewing angle and the position of the wiper at the far CCW end of its arc. I wonder if Tom adjusted the spring (a no-no, I know) which I presume would have held the valve open a pinch more than it o/w would have, at least at idling throttle. Which might reduce the lifetime of this part, which might explain why I'm having trouble today. I'm not going to touch the Potentiometer with anything but Deoxit, regardless. So I'll be cleaning Potentiometer and retesting the AFM and Air Regulator tonight. Hope it doesn't mind if I get contact cleaner all over it (that Deoxit can sprays out hard and its hard to control its hair trigger). Yup I got Deoxit right in the face a few times so I wear goggles now when I use it:laugh: I was also wondering regarding parts interchangeability, Does anyone know if I can use a 1975, 1977 or 1978 AFM in my 1976 car? Or do I need the exact year, or even need to know which model in 1976 to get?

Thanks Tomohawk I'll be sure to ask for the right hoses now.

Tom Thorman of Z Service Unlimited, to be exact! Thanks so so so much for your help!! It's bizarre that Tom would have sealed it like that. That's how we got the car back after he worked on it, and that was the time he warned my b/f not to mess with it (pointing to the AFM cover). I remember that well because he said it in an almost accusatory tone that implied my b/f had tried to tamper with it (I'm nearly positive he did NOT). Since it's so sensitive (and the fact that there's red goop of some kind on the cover that will be Lord-knows-how-hard to take off after all this time ) , I'll take a minimalistic approach to tampering with it. 1. First fully charge the battery as sblake suggested. 2. Retest AFM from the ECU 3. If readings the same, pull off the cover and clean the Potentiometer contacts as sblake suggested. 4. Retest AFM from the ECU 5. If readings the same, not sure what this step will be. Not sure if it would be prudent to open the front hose and manually check the valve's operation, or unfasten the AFM unit as you described (thanks!) and clean the connectors -- if that will even make a difference in the readings I don't know. And 6. Retest again... Step 3 might just be to start my baby up and see how he runs. I didn't mention yet but your car's symptoms were very similar to mine now (as are the resistance results of course!). Though I did momentarily apply full throttle in my neighborhood --funny you mentioned that too -- and it was still running poorly (at idle, part throttle, full throttle, didn't matter :disappoin) I couldn't believe how fast my fuel gauge went to Empty...could six gallons disappear so fast? I was idling in the driveway and the fuel gauge went from about 20% to touching the E line! Perhaps a failing AFM is a great reason to run way too rich (and therefore like crap) but how come I didn't see any black smoke? That still baffles me. Fast Woman I think asked me if my exhaust smelled like gas and it kinda did, but I really don't have a frame of reference to compare it to, to tell if it smelled unusual. It always kinda smells like gas don't it? Did I not thank you enough already? Nope! THANK YOU!!!

Caig Deoxit D5 has done an awesome job on all the connectors I've cleaned so far. Last night I cleaned my water temp sensor, thermotime, oil pressure sensor, fusible links, EFI harness connectors, firewall ground. The water temp sensor was very corroded, and my car's temp gauge wouldn't get higher than about 130-140degF no matter how long I drove/ran it last. My oil pressure gauge always read zero when I'm just idling so I hope cleaning it will make a difference. My fusible links were in bad shape too so I sanded/filed/cleaned them and now they look shiny and new. Tonight I'm going to clean my fuse box connections, bullet connectors, alternator connections, battery posts, and even my horns which are currently off the car! Speaking of horns! HONK!! Anyone answer my newbie questions about disconnecting the plug and black plastic cover on my AFM? I know my question isn't good, but please? Otherwise I'm just going to have to start pulling on stuff. Can anyone who's done it before tell me if there's anything I should know before I touch it? Like...if I should pull the black cover up and out, instead of just out. Or if the connector has a clip I have to pinch. And/or should I disconnect the AFM itself first to have better access to the connector, et al. Advice like this would be so appreciated!!! Anyone? I want to clean my AFM/Potentiator worse than anything but I'll put it off another day in hopes I can get help/reassurance here. PS I can do repairs on my car and have done quite a bit of things successfully already. In time I could be an asset to this forum as much as I am a consumer of it now but I need to learn first like everyone else. I think everyone who has a Z should try to learn as much as they can about them so we can keep these cars on the road, if for nothing else, because we love them! Besides, even knowledge itself keeps the cars alive (keeps cost of ownership down, and by extension, interest in ownership up!).