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Samson

77 280z Water Temp Sensor Issue, Runs Very rough

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Okay, so i attempted to get my car smogged but the CO and HC were ridiculously high, from running rich. Drove it home and just started looking around the engine bay and i saw that the Water Temp Sensor was unplugged! It was missing the connector and all, the 2 black bullet connector wires for the sensor were just dangling around the engine bay, how didn't i notice that before? ugh. Well i'm PRETTY sure they are for the water temp sensor, anyways i bought a connector and a new sensor it was fairly cheap and figured why not, I wired it up and when i connect the sensor the engine idles super rough and if i were to give it some gas it'd just die. If i unplug the sensor, it runs OK. but still running rich, i noticed that even when it's plugged in i don't smell the excess fuel anymore but unplugged i can smell it. Any insight on this?

I've also measured the AFM: i referred to the EFI bible pages (49-51) Okay, the measurement #1 was pins 6 & 8 now this was from the ECU plug( All three measurements were) which was 321 Ohms the EFI bible says measurement should be at approxiamtely 180 Ohms so.. that is definately not righ?, measurement #2 which is pins 7 & 8 257 Ohms EFI states should read (Continuity, small resistance) measurement #3 Pins 8-9 measured 145 Ohms EFI bable states should read approximately 100 Ohms. I haven't actually measured from the AFM itself but i did clean out the flap which Air flow Meter Cleaner.

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Your plugs are probably really fouled with carbon. Clean or replace then troubleshoot.

You know what, my plugs actually are really fouled with carbon. But they only have i'd say about less than 10 miles on them. Could just changing them to new plugs hopefully correct the problem? How would i go about cleaning them? I know there are "spark plug cleaners" but is there a method i could use with basic tools? Could i just go about wiping them with a towel? Ha. Thanks! If the plugs are the culprit i sure hope it fixes the problem. How does my AFM measurements look?

Also just to note, i started to inspect the engine bay more closely and noticed the hose for the PCV valve was horrible, it has a crack at the end that goes into the PCV valve and seems to be wrapped with foil, then electrical tape.. sigh. I guess i'll be replacing that too, now would i have to get a 280z specific PCV hose? because it has a bend to it, or i'll be fine with just some normal 5/8 hose from the parts house? Thank you all in advance.

Picture of the hose

post-28105-14150820853997_thumb.jpg

Edited by Samson

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My guess is something has been adjusted to account for a SUPER!! rich condition. My car will hardly run with the WTS disconnected. So with youre repair you are now running lean. This could be caused by a vacuum leak (not unheard of at all) or the AFM could have been tampered with in the past. I would check for vacuum leaks first then investigate the AFM sweeper next. Changing out the plugs will not fix the problem but they have indicated that you were running rich before youre repair. Also try some of the more simple tune ups to see what happens, like the idle speed adjust, TPS function etc. Good luck and keep posting results, a solution will come up.

Edit: You are on the right track testing the resistance at the ECU connector. and it does suggest that something is amiss with the AFM' signal, You may just want to take a look inside the AFM carbon sweep cover, maybe even post a pic for comparison.

Edited by grantf

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My guess is something has been adjusted to account for a SUPER!! rich condition. My car will hardly run with the WTS disconnected. So with youre repair you are now running lean. This could be caused by a vacuum leak (not unheard of at all) or the AFM could have been tampered with in the past. I would check for vacuum leaks first then investigate the AFM sweeper next. Changing out the plugs will not fix the problem but they have indicated that you were running rich before youre repair. Also try some of the more simple tune ups to see what happens, like the idle speed adjust, TPS function etc. Good luck and keep posting results, a solution will come up.

Edit: You are on the right track testing the resistance at the ECU connector. and it does suggest that something is amiss with the AFM' signal.

I've removed the AFM the other day and cleaned up the connections, and i did look at the atlanticz AFM adjustment article but i was too afraid to start tampering with the wheel, but it looks "untampered" with that blob of glue looks factory on it. What i did notice though was that the bypass screw on the AFM was backed all the way in, i did try to "tune" the screw backing out and in but it doesn't really make MUCH of a difference. Car just idles horribly, and if i were to try and rev it, the engine would just cut off. I've also cleaned the TPS contacts already aswell. The distributor cap has been replaced. Is it possible that the PCV hose or valve itself maybe causing the problem? When i removed the valve it had tons of crud all over it.

Edit: Just to note i did take the car thinking it'd pass smog a week or two ago.. here were the #'s that lead to the obviously rich condition HC was measured at 405 max is 214, CO measured 5.49 @ 15mph. The 25mph test for HC it measured 435, max: is 181. CO measured 7.53 max is 1.16. Just thought it'd give a better idea..

Edited by Samson

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The purpose of measuring at the ECU connector is to see what the ECU sees. The numbers you measured are not what the ECU is expecting, so now you should measure at the AFM. If the numbers at the AFM are the same as at the ECU connector then the problem is in the AFM. IF the AFM measures differently (hopefully correctly), then the problem is in the wiring and connections from the AFM to the ECU.

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The purpose of measuring at the ECU connector is to see what the ECU sees. The numbers you measured are not what the ECU is expecting, so now you should measure at the AFM. If the numbers at the AFM are the same as at the ECU connector then the problem is in the AFM. IF the AFM measures differently (hopefully correctly), then the problem is in the wiring and connections from the AFM to the ECU.

I agree with your post. I'll get some measurements tomorrow, I sure hope I don't have to change out all the wiring.. the PO did redo all the EFI wiring though, but its half assed work. There are tons of excess wiring on the driver side footwell, looks like a rat's nest.

Also, about vacuum leaks.. I do remember there was this hissing noise comming from the brake booster area, like between egr valve and brake booster somewhere are there.. is this normal?

Edited by Samson

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No the hissing is not normal, and should be looked at, but I would agree with Zed Head regarding further testing of the AFM, this may lead to a possible culprit. You're statements regarding the P.O. hack wiring brings up a real good possibility also.

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Okay, so I've finally had the time to work on the Z again i did the measurement pin 8 & 6 at the afm an it was about 183-187ohms around there so that's within specs right? As for 8 & 9 it was around 105-120 ohms.. hard to get a reading on those stupid pins..

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If you think your AFM is out of calibration, this will get you close:

With the engine running:

1. Stand by driver's side wheel

2. Take cover off AFM

3. Press throttle linkage to hit ~ 3,000rpm

4. Note where the AFM's wiper contact goes on the carbon trace.

5. Manually move the wiper further CW or CCW buy turning it with your finger at at the counterweight.

6. If the car runs faster when the wiper rotates CW then you are running too rich and must tighten the AFM spring.

7. Repeat 3 to 7 until it is running right.

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Your AFM numbers look great, ~100 and 180 ohms. I wouldn't mess with adjusting the AFM at all until you get the ECU connector to read the same as the AFM. From your previous post, it looks like you might have corroded connections between the AFM and the ECU. The ECU connector numbers should match the numbers directly from the AFM within an ohm or two.

Until you have the electrical connections between your coolant temp. sensor and the AFM cleaned up, don't touch the insides of the AFM at all. You'll be getting way ahead of yourself.

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Okay, so the car has been sitting for about a month since last i've started it. Today, i've replaced fuel filter, spark plugs, wires, replaced majority of vacuum hoses, aswell as the radiator hoses, replaced the AAR connector, CSV connector, and WTS connector and i've added a maxi fused block as a replacement for the fusible links that were SUPPOSED to be there but the previous owner for whatever reason decided splice all (4) white red stripe wires to the (4) white power wires having it not fused i didn't like this so i added the fuse block.

Anyways onto the problem now. The car doesn't start no more this has happened before i don't hear the fuel pump kicking on the car will attempt to turn over but no sound of fuel going in, but at one point there pump kicked on for a couple of seconds but it went off. What can it be now?

Thanks

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There is a small contact switch in the AFM that has to close to make the fuel pump run.

Take the cover off the afm then move the wiper assembly by hand and observe the reed switch to close. Do this with the key in "run" and you should hear the fuel pump and rush of fuel if all is well. If not then check electrical paths.

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There is a small contact switch in the AFM that has to close to make the fuel pump run.

Take the cover off the afm then move the wiper assembly by hand and observe the reed switch to close. Do this with the key in "run" and you should hear the fuel pump and rush of fuel if all is well. If not then check electrical paths.

I will definately try that. The last time it had this same issue i remember checking the oil dipstick and it was dry that was about a month ago when i first bought the car i did a simple oil change and that seemed to fix the problem. This time i know there should be enough oil in the car by the dipstick because it's full.

?

Note: The volt meter in the dash is also unstable.. the light will flicker and the needle will bounce. Could it be possible that the battery is ka-poot? I did test the battery it showed about 12.46 volts and did a crank test and it was at around 10.46 volts

Edited by Samson

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Okay, so i got the fuel pump to kick on, to find out the power wires from the fuel pump were snipped and the Previous owner just got about a 16 gauge wire and ran it from the pump all the way to the front of the car to the inside fuse box and had it wrapped around the AC fuse i believe it's the air conditioner or fuel gauge. Fiddled with that and changed that fuse and wah-lah the pump kicked on. Now, the car still doesn't want to turn over. I know it should be getting spark because the plugs are new aswell as the wires..

Also, What would be a correct way to wire the fuel pump? Thanks

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The fuel pump on my 75 runs off the ignition to start and then off the AFM don't know about a 77. If it won't turn over try re-checking the battery, if its OK try to jumper from the battery to the starter, take a 14-16 gauge wire from the + battery to the little post on the solenoid on top of the starter.

Edited by mjr45

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The fuel pump on my 75 runs off the ignition to start and then off the AFM don't know about a 77. If it won't turn over try re-checking the battery, if its OK try to jumper from the battery to the starter, take a 14-16 gauge wire from the + battery to the little post on the solenoid on top of the starter.

Hmm okay, I will try to bypass the ignition but I mean the car did turn over about a month ago just not doing it now since after I changed all the stuff.. at one point the car turned over but at super fast idle and it died, noticed a super loud hissing noise aswell. My afm has that fuel cutoff switch if I move counter weight i can hear a click

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Samson, it frankly sounds like your car has been butchered by previous owners. The L-jetronic fuel injection system is pretty basic/simple, and it can be put back into shape by going through it with a fine-tooth comb (including the intake). If I had to take a guess, I'd say you have a massive vacuum leak (loud hiss) that would ordinarily make the engine run way too lean. However, with the CTS unplugged, the lean condition is compensated, so that the engine will run (poorly). In fact it is overcompensated, so that your plugs foul with carbon after only 10 miles. Both a vacuum leak and bogus temp input are problems. You can't properly fix one problem by introducing another that works in the opposite direction.

I'd recommend the following as a matter of course:

(0) Drain old gasoline and replace with fresh. Replace fuel filter and inspect for lots of rust (could indicate rust in gas tank clogging up system). Replace air filter.

(1) Make sure your intake is air-tight. See post 11 in this thread for a quick method (my "yogurt cup test"):

http://www.classiczcars.com/forums/thread43280.html

Likely culprits for vacuum leaks are rotted vacuum lines, your rotted PCV hose, and a leaking intake manifold gasket. Brake boosters sometimes leak as well.

(2) Make certain all of your EFI components check out. Measure all the resistances, and do all the checks described in the FSM.

(3) Check your distributor vacuum advance to make certain it's not frozen up.

(4) Change out your plugs, wires, cap and rotor. Use NGK plugs and wires. Verify spark.

(5) Adjust your valves, and set your timing (if by this time your engine runs, which it probably should).

This all amounts to a major project, but that's what it will take to get your engine running well. Until you do all of this (and more), I don't think you have a prayer of passing California emissions. Heck, my own engine runs like a top, and yet I wouldn't bet my life it would pass your state's emissions tests. So because you'll have to do all this stuff eventually anyway, it's better to go ahead and do it up front. Then you will have worked your way past numerous pitfalls and will be dealing with a much smaller set of reasons your CO or HC might be a bit high, etc.

Edited by FastWoman

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Sorry for the long awaited response but i finally had some time to work on the car within the week, and i got the car to fire up! Re did the fuel pump wiring, traced the wiring back from the fuel injection relay back under the passenger seat where the wires were snipped, routed the fuel pump wires back into the car and wired the wires accordingly. Removed the "hot wired" fuel pump wire and turned the key over and she fired up! The voltmeter in car kept fluctuating, got my DVOM and measured the alternators output and got a wopping 11.35 Volts! that is not good. Bad alternator so i had to get that swapped out changed the belt aswell because that was in horrible condition. Now reads at around 14.35 Volts. Drained coolant, replaced thermostat and gasket went to retighten bolts and the damn things stripped, but i didn't notice it at that point in time i had my buddy's 78 AFM that he let me borrow on, start the car seemed to idle at around 1300 then slowly started dropping to around 8-900 or so.. but after car would reach operating temp coolant would shoot out the thermostat cover, so i had to helicoil the threads now they're good as new. I definitely think the AFM that came with this car was no good if it was able to run "okay" with my buddies on. Didn't get to use my buddy's AFM this time because i had done returned it, but a AFM i bought off a member on another forum came in and i had that installed. Put a fuel pressure gauge on, vacuum gauge, started her up once more. Idle's at around 1500-1700 and stays like that through the whole way pretty much even after operating temp is reached. Fuel pressure gauge shows around 31-34 psi it fluctuates tho, but when i rev it shoots up to around 40 psi. Vacuum gauge shows a steady 20-21in HG. I did notice there is a very VERY small leak between the throttle body and intake manifold it's like comparable to the diameter of a toothpick. When i turn the vehicle off the fuel pressure would slowly decline to 0. Whats the deal with that? Also, when i would snap the throttle a puff of black smoke would shoot out so i'm guessing it's still running rich? Sorry about the long story!

Edited by Samson

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Hmmm, I am getting rusty on this since I have worked out most of the bugs on my 77. A leak at the intake manifold would cause a vacuum leak, this would lead to a lean condition, but youre vacuum reading does not seem that bad. Fuel pressure drop after turning off the car would seem normal after sometime but not immediate.

Have you adjusted the idle speed yet? Has youre new AFM been adjusted to run rich? TPS adusted properly?

Edited by grantf

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Hmmm, I am getting rusty on this since I have worked out most of the bugs on my 77. A leak at the intake manifold would cause a vacuum leak, this would lead to a lean condition, but youre vacuum reading does not seem that bad. Fuel pressure drop after turning off the car would seem normal after sometime but not immediate.

Have you adjusted the idle speed yet? Has youre new AFM been adjusted to run rich? TPS adusted properly?

Okay, well I haven't messed with the AFM whatever the previous owner had it at I just left it and installed. The idle adjustment screw has been adjusted, its pretty much turned all the way in with no more adjustment available, as for the TPS I have not adjusted that given I don't know how, ha. I know there's a write up on atlanticz. I hear many people wire in a potentiometer into the WTS, what if I did that and lean out the mixture? I have a 5k pot I purchased.

Thanks for the response.

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I would suggest that you make sure all of the EFI systems are working properly before tricking the ECU. Only after you are sure would you consider inriching the mixture with added resistance.

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You can only make the mixture richer by adding an inline resistor. But, as grantf suggested, it looks like you still have basic problems to get right before any tweaking should be considered. Your fuel pressure, for instance, should not be jumping to 40 psi. Maybe you're just seeing the needle bounce. You can test it by removing the vacuum line from the FPR while the engine is running, or removing the wire from the solenoid and turning the key to Start. It should be about 36 - 38 psi. If you can't get the engine to die or almost die by turning the idle screw in then you have a vacuum leak somewhere. If you have a vacuum leak and it's still running rich, then you have a fuel enrichment problem, either through too high fuel pressure or something like the TPS or coolant temperature sensor circuit.

Lots of basics to get right before tweaking the AFM or installing a resistor. There's really no way around it. I've not read any posts where someone reported that they tested and measured the circuits described in the Engine Fuel chapter, and wished that they hadn't because t was a big waste of time. It's worth doing.

The fuel pressure dropping to zero is more of an irritation than a problem to worry about. It's pretty common and there are fixes for it, but that's not your main problem. Get a meter and start probing. Good luck.

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Okay guys, was able to mess with the z for about a half an hour today and i think i found the problem to the fast idle it was having. The throttle is sticking! Just to note this is not the stock throttle body, the PO had installed the 60mm throttle body, there is a spacer that's suppose to go in between the throttle body and intake manifold but i had that removed because that was blocking off the AAR hose that goes into the throttle body so i don't see how that was suppose to work? Unless it was designed like that? .. I noticed when i would hit the throttle the Pivot ball looking thing on the throttle linkage it would not go back "all the way up" There is some play from the throttle body and the throttle linkage. If i would hit the throttle it would go normal but after i let go it would stick and stay at around 1400 RPM, If i fiddled with the Pivot ball thing moving it up very slightly and the idle would drop back down to 900-1000. The idle adjustment screw seems to have fixed it self or something because it seems like it still has some turns that'd drop the idle slightly, but if i started turning it in more i would hear weird noises, i may need a valve adjustment? Also filled in that small leak between throttle body and intake manifold with some RTV ain't the best looking but it seemed like it worked. I have some pictures attached of the linkage... How would i go about fixing this? Or is there adjustments to be made..

Thanks all!

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Edited by Samson

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First thing I notice from the pictures is the throttle return spring is totally incorrect, both in its location and style.

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