77 280z Water Temp Sensor Issue, Runs Very rough

[Samson]

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.

[240260280z]

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

[Samson]

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

Edited October 18, 2012 by Samson

[grantf]

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 October 18, 2012 by grantf

[Samson]

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 October 18, 2012 by Samson

[Zed Head]

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.

[Samson]

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 October 18, 2012 by Samson

[grantf]

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.

[Samson]

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..

[240260280z]

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.

[Zed Head]

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.

[Samson]

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