My 1976 280z won't rev past 3500 when not in gear, and about 2000 when in gear. When in neutral it will blow clouds of black smoke at higher rpm. It has run way to rich like this since I bought it. I have checked the wiring and sensors and rectified the issues I found to no avail. The water temp sensor was the first place I looked, I replaced it when I first got the car. It is giving the correct reading all the way to the ECU and has a noticeable effect when I unplug it. My only guess would be a AFM, I have two but don't know the condition of either. They both passed the ohm tests, could there still be an issue with them? If not what else could be causing such a rich condition, especially at higher rpm.

Make sure the vane is moving easily behind the black plastic cover and the wipe path is clean and dry.  On the AFM. 

fuel pressure? CSV checked and work right?

Edited February 15, 20187 yr by Dave WM

The whipper moves free, if I hold it closed a little it doesn't really get better. The fuel pressure is correct and I have a gauge in place of the cold start valve as I live in a warm climate. 

OE fuel injectors? TPS?

Tps has the cover removed but does work, I have it adjusted correctly and it has passed both tests. I believe the injectors are this set, except for one that was dead when I got it so I replaced it. They all have the correct resistance and don't show a huge difference when I pull and inspect the plugs. 

try another AFM if that does nothing I think the FSM calls for a new ECU once everything else has checked out.

I've got 2 AFM's and 2 ECU's and no combination of those works. My hope is that a known good AFM will solve the issue.

Edited February 15, 20187 yr by 240DL?

I would think it has too, did you try testing the AFM to see if the resistance varies with movement? compare all three if they do the same thing its likely they are all ok.

Edited February 15, 20187 yr by Dave WM

Dumb question, you do have the ground wire secured right?

 

The only test I can find for the vain itself is a voltage test. Is it possible to check simply with resistance if it is functioning correctly?

Sure would be upsetting to find that ground wire to be the issue. One AFM has a ground wire while the other does not? I will try the one with the wire grounded well but I doubt that is the issue as I recall checking that a while ago

this is what I did, best to use analog meter, I setup a simple voltage divider using some 9v batteries. Hopes its just a ground wire, but if you are still getting no where after checking that, you could get all 3  out on the bench and do a test like this.