FastWoman

For the most part, what determines your fuel delivery is the air flow through the air flow meter, the readings of the other sensors (for fine tuning). The ECU does its computations based on these, and it delivers a pulse width to the injectors that is directly proportional to the amount of fuel to be delivered. If it's functioning properly, the fuel pressure regulator maintains a constant pressure differential between the fuel rail and the intake manifold. That constant differential results in a known delivery of fuel for a given pulse width. If your manifold vacuum is low, the pressure should regulate higher, so as to deliver that constant flow rate. Your system has so many mods that I wouldn't really know where to begin with it. However, the fact that the injectors are "high flow/pressure injectors" suggests to me that their flow rate is foreign to the ECU. I think that's a huge potential problem, and you should verify that the injectors deliver fuel at a roughly ordinary rate when switched on. Before you invest lots of time in pursuing that avenue, however, I'd check the connection to the coolant temperature sensor. If you have a bad connection there (or a bad/open sensor), you'll experience EXTREMELY rich running -- black smoke out the tail pipe, very bad idle, etc. -- just as you've described. Those electrical connectors get pretty crumbly, especially on the front of the engine. I think you would learn the most by pulling the connector off of your ECU (and not touching the temp sensor yet). Measure for conductivity between pin 13 and ground. It should be in the neighborhood of a couple of kohms cold, give or take, depending on temperature. If you read an open circuit, there's your problem. You'll probably need to clean up the connector to the water temp sensor (the smaller of the sensors in your thermo housing with two wires -- not the one with the single wire). The other place I'd look is your cold start valve. It might be stuck open, or the thermotime switch (the other two-wire plug in the thermo housing) might be having issues. Anyway, I really doubt the radical cam is to blame for the rich running. The pump may be rather high pressure, but I suspect the fuel pressure regulator can handle it. (Just measure the fuel pressure to be certain!) As far as you know, did the modified engine ever run right?

Thanks, Al, but isn't fiddling with the oils just a way of buying time? With a leaky front seal, 165k on the original clutch, and synchronizers that are that fussy, am I not at a point where I really need to pull the stuff out and rebuild it anyway? I'm not planning to do it tomorrow, mind you, but I think it might be a spring project, whether I do it myself or farm it out. (I'm leaning more towards attempting it myself.)

That would make it a pretty cold, dry day in Houston!

Well, it sounds worth considering. About how much does a 5 speed weigh, give or take? And about how much time should I budget myself for a transmission and clutch rebuild? Tlorber, I appreciate the kind offer of your vice frame. I might take you up on it yet.

Scott, I did a relay conversion on my '78. The relays fit very nicely inside the relay box where the fusible link housings are attached. The wiring dropped down into the large harness below. You wouldn't know it's there. Details are buried somewhere in this thread: http://www.classiczcars.com/forums/showthread.php?t=35588&highlight=breakers

Well, that's encouraging. I'll study it. Maybe I'm up to the task. How hard is it, physically, to pull a transmission? Is it something a sturdy old lady can do?

Thanks, guys! I think what I'm hearing is that the transmission is weak/worn, but that I can possibly nurse it along for a bit longer with Redline. I might try bleeding the clutch too. I hadn't considered that a mooshy clutch could result in too shallow a lift, but that makes sense. Even so, I think all this just buys me time. Right? If I'm going to keep the car for a long time (which is my plan), it sounds like a transmission rebuild is in my future. Until I can address this issue (probably in the spring), is the occasional bump/grind (by 2 or 3 teeth) is going to destroy the gears in the transmission? Until then, I perhaps need to consider a rebuild, not only for the synchromesh, but also for the seepage from the front seal. A new clutch would also be an obvious thing to do. I'd probably find a transmission shop to do the work, all things considered.

It's not a shifter sloppiness issue, Cozye. I haven't looked at the shifter bushings, but they feel solid (surprisingly so). I had replaced mine a couple of times in my old '75, so I know what a difference that makes. BTW my old '75 had the 4 speed like yours, and that shifted fine. Now I have the 5 speed, so really I have no prior experience with this transmission. I wonder if it's ordinarily any stiffer than the 4 speed. (I doubt it, but...)

Wow, congrats, Cozye! This inspires me to take care of a couple of back-burner issues -- differential mount, gronky steering column, mystery transmission issue (see other post). Still, I think I can share your ecstasy when not milling about in a tight parking area or shifting gears! I can't help but smile when I drive my Z.

Hi all, OK, this is bugging me, so I'll ask you guys what you think. I have a '78 280Z with a 5 speed. When the PO showed me the car, he warned me that the clutch engaged very close to the floor. It did -- VERY close. I later found the lock nut on the clutch pedal's push-rod had come undone, and the rod had screwed itself looser and looser. I corrected this and adjusted to specs. When I bought the car, the transmission shifted a bit stiffly, but there was no gear bump/crunch between any of the gears. After I drove the car for a while, the transmission shifted a tiny bit more easily, but at the same time it developed a small grind when going into second gear from 1st -- perhaps a couple or three teeth. I resolved to change to change the transmission fluid to get a hint what was going on. Unfortunately the plugs were practically welded in place. I couldn't budge them and put off that job. Later when I had the local Z specialist install an exhaust for me, I had him change the transmission fluid and asked for his opinions about the problem. He changed the fluid with Mobil 1, and he no problems with the fluid (no filings or debris). He identified a slow oil leak out the front of the transmission into the bell housing and said that was the cause both of my clutch chatter (I doesn't chatter when I drive it) and the 2nd gear grind/bump. He said I might also have a clutch issue, whereby the transmission doesn't fully disengage. He insisted that the transmission was fine and that my suspicion that the synchromesh was worn was probably not true. The fluid change and further usage have done nothing to help this issue. The transmission continues to bump/grind every now and then when going into 2nd gear, even with the clutch pedal to the floor, and shifting continues to be rather stiff between all gears. (Caveat: I've been used to driving an original Saturn stick since 1991, and that clutch shifts like butter -- easiest stick I've ever driven. So I might not remember the Z clutch too well.) If it means anything, the bump/grind problem doesn't occur until after a day or two of driving if the car has been sitting any longer than a week. (That's probably why the problem didn't show itself when I was first inspecting the car, prior to buying it.) Anyway, as far as I can tell, the clutch DOES entirely disengage when I depress the pedal. I have to release the clutch an ordinary distance off the floor before I get any grinding/bumping when shifting lightly from neutral to reverse. Reading more about synchromesh, I find it can get worn out if the clutch is not entirely disengaged when shifting. Well, with the clutch pedal practically to the floor as driven by the PO, that could easily be the case. So I'm again wondering, is it a clutch disengagement issue or an oily clutch issue, as the local Z specialist seems to believe, or is it a synchromesh issue? And if it's a synchromesh issue, is it rocket science to rebuild the gear assemblies, or is that something I should farm out to a transmission shop? Or is it better just to swap for another good/used 5 speed? Thanks, everyone!

Sounds like it might be a rough/bad/damaged bearing.

But wait... Now that I think about it, maybe the wiper switch was used by the PO as a defeat mechanism to keep the car from being stolen. Maybe it was done on purpose and isn't a short inside a melted section of harness. I suppose there's hope. Unfortunately I don't know much about the wiring of the main power feeds in the '76. All I can suggest is to check your fusible links and possibly the ignition switch. I think I'm safe in saying the main power lines are the large white and white/red-trace wires you might encounter. You definitely need to start with a factory service manual for your year of Z, which you can order used off of Ebay or Amazon. You can also download a FSM for free somewhere, but there's nothing like having paper in front of you.

It might be possible to use the molding rubber to stick the halves together. The inside surfaces of the guards would have to be sanded/roughened, of course, and probably some connecting mesh would be a good idea. Another possibility would be black 5200 adhesive/caulk. It's the toughest, most tenacious stuff I've ever used. It's the duct tape of the boating world. I suppose if the stuff started to fail, you'd get a bit of warning (small areas of separation) before actually losing half of your bumper guard on the highway. No idea about the rubber plugs. Maybe rubber stoppers, cut to size? They sell black rubber stoppers in various sizes at my local True Value.

Reminds me of an Olds Cutlass $500 special I once bought for the sole purpose of instructing a new driver (a very bad one). Big, tough, cheap = perfect. Unfortunately the electric was pretty scary. Aluminum foil had been stuffed into the fuse box. There were melty sections of wiring, and there was a lot of weird stuff like your windshield wipers energizing the fuel pump. In hindsight, if I were going to keep such a car, I would just rewire the entire thing. I'd buy one of the reproduction wiring harnesses, yank out all the flakey wiring crap, and just replace it all. In the process, I would upgrade to headlight relays and install a heavier alternator output line. I think that would be easier than tracking down all the individual problems AND keeping your electrical system functioning in the long term. Of course I haven't seen your electrical system, so maybe it's not as bad as all that. However, from a distance, it sounds pretty scary. If that work is beyond your budget, then I'd recommend going from stem to stern on your car and unwrapping/inspecting/repairing/refreshing/re-wrapping every inch of wiring harness. Look for melted spots, funny burnt smells, cut and broken insulation, corrosion, CREATIVE MODIFICATIONS (ahem...), and anything non-OEM. Using your FSM, restore everything to stock. If you have to do any patchwork, learn to do solder connections with heat-shrink insulation. It's quite easy, and it's superior to crimp connections.

Tomo, see post #16. I've never used the stuff personally, but this sounds like a promising approach. I'd personally rather try to create a new part than to hack up an old part. Which little round plugs?

You can probably straighten the thing in a very controlled manner by bolting it down (on the ends) to the narrow side of a wooden beam (e.g. 2x6) that you've radiused with a hand planer. You can start out with a very mild radius, bolt it down, remove, measure, steepen the radius, bolt down, remove, measure, etc. When you've JUST started to bend the thing, you've just gone into strain. At that point, you can figure out how much farther you need to bend it (e.g. 3/16" more on the ends), steepen the radius by that same amount (e.g. another 3/16" shaved off the end), bolt it down, and you should be done. (It might be good to bend it close to the mark first, and then make the final adjustment in another pass.) If it doesn't flatten out satisfactorily, then maybe the machine shop can mill it flat. However, you won't have lost anything. That's approximately what the machine shop would do (except perhaps without wood) before milling the flange. You can probably even return it in the re-bent shape, as your bends couldn't be any worse than the manufacturer's, and I doubt they would even notice.

I like that idea, ajm. In fact I wonder if a turn-buckle could be incorporated to adjust the shock compression. Hmmmm.... On a previous topic, a thought about the bumper guard: Maybe the humps on the pictured rear guards were cut off, sanded smooth, and polished?

Thanks, Texas! Yeah! That looks sharp! The rear bumper guard has a different shape (other than having a couple of ribs removed) than the stock '77/'78. Specifically, it doesn't project out in a dorky mound. Rather, it just covers over the end of the bumper. I'm wondering whether this was some sort of custom-molded bumper guard. For reference, here is the stock look -- same as mine: http://www.triadzclub.com/z/classifieds/Mar%2013_08/1977Datsun280Z/index.html Having thought about this a bit more, I'm wondering whether I could compress the shock to the length I want, drill a hole through it someplace that won't compromise the mechanics of the shock, and put a small diameter bolt through the whole thing to keep the shock compressed. In the event of a collision, the bolt could shear, and the shock might still provide some shock-absorption protection. If desired, the bolt could be removed to restore the bumper position to its stock configuration (also replacing the original bumper guard). I'm thinking I'll be able to mold my own custom bumper guards, but I'd love to find the pictured ones ready made. Do you know if they exist somewhere?

For a pin? Nah... Ace is the place (or at least True Value, in my case). I'd be surprised if I can't find what I need there. I might have to drill a hole for the R clip, but no biggie.

I can reach the clevis pin, no problem -- seat all the way back, and doing the limbo on my floorboard (not easy for an old lady with arthritis). However, the hole is worn both in the clevis and in the pedal. I've got to get the pedal out to fix it right, and therein lies the problem. Anyway, NEXT SPRING!! We're not used to cold here either. It just dipped down to freezing last night. We're starting to suffer! Gotta put heaters in the boats today.

Better fix that before you provoke a road rage incident! I agree with Gary. Check where sections of harness pass through holes in sheet metal. You might be missing some rubber bushings somewhere, and the sheet metal could be cutting into the wiring. If there's a short to ground anywhere between your horn button and your horn relay, your horn will sound. So you might check that pathway. I know it's a PITA, but you might consider unwrapping suspect sections of your wiring harness to inspect the integrity of the wiring. Especially unwrap anything that looks previously unwrapped and any sections with bulges, and unwrap whatever work the body shop did. Your problem has got to be in there somewhere. When you're done, break out a roll of electrical tape, and wrap it back up. I've read other people commenting about the fuel gauge fluctuation. My car doesn't do it, but I suppose it happens sometimes.

Ztrain, I'll give it all the consideration it deserves! Kenny, I'm wondering if the pedal assembly was redesigned in the later years. My hands are rather ordinary size, and I'm hard-pressed to even touch the fulcrum pin with my fingertips. Maybe I'd have more room by removing the vent ductwork. There's also this solid partition between brake and clutch that almost completely obscures my view. Anyway, this job has now landed on my "put off until Spring" list. It's cooooold outside right now! Agreed, BTW, about those Ace and True Value stores. They have some very iimpressive fastener selections. We live on the water and use LOTS of stainless. I can buy stainless fasteners there by the box.

Congrats on tackling that frozen bolt! The danger isn't rounding off the head, so much as snapping the shank. Rust and age take their toll on these old bolts, and they're often not as strong as they used to be, while having to stand up to enormous torque when twisting them out of a corrosion-packed hole. You'd be very smart to buy a set of stainless steel bolts and nuts to replace the original ones. Alternatively, you can find a surprisingly good assortment of stainless fasteners at most small-town Ace and True Value hardware stores -- much better than at the big stores like Home Depot. When using them in aluminum, you'll definitely need to use nickel anti-sieze. Also you can't use stainless for some of the really high-demand applications like manifold and head bolts. However, you CAN use the anti-sieze. I suspect your original thermostat wasn't seated carefully when it was installed. I've never see a thermostat jammed into the housing that way, but of course I've only replaced a handfull of thermostats in my lifetime. The water pressure shouldn't be enough to bend a thermostat. My guess is that the thermostat was bent when it went in, which was why it didn't seat properly. Either that, or it was somehow bent when the shell was bolted down on the improperly positioned thermostat. Your spark plugs look a bit like mine did when I was running very lean. I was fooled by the carbon buildup on the plugs, but I think the cause for that was the incomplete combustion of my lean mix before the exhaust valve was opened. Lean mixtures burn much slower than proper mixtures. I think the really slow burn was also what resulted in the hard puffs in the exhaust. (I think the continuation of the burn even when the intake valve opens is what detinates the intake gasses, resulting in backfire.) My engine was full of carbon sludge, BTW, probably from the same problem. Now that my fuel /air mixture is richer, I'm getting more rapid, complete burning. My plugs look much, much cleaner now. Anyway, what the plug-reading charts don't generally show you is the appearance of a plug in a super-lean-running engine. Vacuum hoses: Yes, keep replacing them. You should have them all replaced. I guarantee you they're worse than they look. Don't forget to check whatever is hooked to the vacuum lines for leaks too. For instance, my HVAC control system was leaking. I even had some unplugged vacuum hoses under the dash. I started a thread a while back about how to refurbish the vacuum controller switch (the HVAC mode selector). It's easy, but requires a bit of disassembly to get to it. Also, if you're not going to take off the AFM to do the vacuum check, at least make sure to check the big rubber boots for cracks and splits. Use a mirror to check their undersides, and stretch the bellows a bit to look at the folds deep inside. If they're split, you can buy a new pair (should probably replace in pairs) from MSA for about $100. If they're not, consider yourself lucky, and spray them lovingly with a bit of Armorall or (better) silicone oil spray to keep them soft. Electrical connector clips: They're not as prone to fly through the air as you might expect. The best approach is to undo one side, rotate the clip partially around the connector, so that the wire on the other side pulls out slightly, and then hang the end of the clip on the side of the connector. You can then unplug the connector without the clip coming entirely off. Reseat the clip immediately afterwards, so you don't lose it. IF you lose the clip, you can duplicate it with some spring metal. I don't know whether you can find a paperclip fine enough to work, but you can certainly find some suitable spring wire at a hobby shop (which would work much better). Just bend yourself a new one. Just a bit of perspective on the lean/rich thing... with which many people might take issue: If you're going to race this car (not implying you're going to), you can do huge damage to the engine by having a mixture that's too lean. However, for ordinary street use, it's not as huge a deal. The intake backfiring does beat up the AFM, but generally not beyond repair. (You DON'T want backfiring!) The hot running is rather hard on the valves, but won't immediately kill them. Your engine will last longer between rebuilds if it's running right, but lean running is nothing that will kill your engine tomorrow. Performance will of course suffer. Just remember that MOST Z engines don't run very well, because they're not in proper repair. As evidence of this fact, my engine was running a bit worse than yours, from what I can tell, when I took it to my local Z guru to have him fit a new exhaust. I asked him go over the car from stem to stern to find anything else that needs addressing. His summary was that "The car runs really good." (Hmmmm.... OK.) So I drove it home and got to work on making it run the way I wanted it to. NOW, after havng fixed a massive intake leak (intake/head junction), replaced a coolant temp sensor (reading too cold), replaced cracked intake boots (big leak), adjusted the AFM (idle mix screw way out of kelter), replaced a frozen (open) cold start injector, replaced the injectors (dribbly/leaky/VERY old), replaced the fuel pressure regulator (too low by a few psi), replaced all of the electrical connectors (some of which had fallen apart), and adjusted the mixture with a variable resistor, I've gotten it to run "really good," with far more power and far cleaner exhaust. The engine runs smoothly, with no hesitation, misses, puffs, etc. It's feels/sounds a lot like the little BMW Z3 I recently sold, except with somewhat less power (smaller engine, half the valves, a few generations less sophistication). I'll go further to mention that the Z3 ran to the satisfaction of dealer mechanics before I replaced a coolant sensor and cracked intake boot and freed some sticking valves with a few motor flushes. After I was finished, it ran like a Ferrari. My point is that most people, including professional mechanics, don't know how an engine should run. They feel if an engine is old or has lots of miles on it that it can't run well, and that you should be satisfied that it gets you down the road at all. People drive engines like that for many years, and the engines manage to deliver, even in a state of perpetual disrepair. So your engine probably isn't going to fall apart if you continue driving it the way it is. It just won't be performing to its full potential. Keep chipping away, and your engine will run better and better. Meanwhile, don't be afraid to take it out and enjoy it.

Wow, violent.

Drum roll please.... And the winner is.... a worn clevis and/or pedal arm hole! ... not that I took it apart, but I could feel where the pin had worn an oblong hole in it that would pop if I pulled it the right way. The obvious solution is to pull the pedal out, drill a larger hole through the pedal and clevis, and fit a larger pin. Anyone got an 8-year old who wants to earn some money? BTW, Nissanman, I'm guessing you have right-hand drive in your Z. That would make working on the clutch pedal a LOT easier. I'm just not a good enough contortionist to cram my hand into that small space, shine a light where I'm working, and actually crane my neck beside the kick panel far enough to see much. Removing the clevis is easy, but removing the pedal could be more challenging. It looks like the easiest approach might be to pull the brake/clutch pedal assembly by unbolting the masters, removing a bolt under the dash, and dropping the whole thing down. But I won't be getting into that for quite a while. Maybe the noise will go away before then! Anyway, thanks guys! At least now I know what the problem is.