Need Help, Running rich...

[fixxor]

I have the EFI Bible, FSM, this forum, and hybridz.org. Searched, read, tested and stumped. 78 280z just got it. Here is what I've replaced:

Cap

Rotor

Wires

Water temp switch

Fuel Pump

Injector, water temp, thermotime, tps, cold start valve connectors.

Cleaned prongs and all that jazz.

All fuel hoses replaced.

All vacuum hoses replaced.

PCV valve and hose

Here is what I've done, tested/story behind all this.

I got the car, it was starving for fuel. Replaced pump but still starving. Gas tank all rusted up so took it off and cleaned it Now getting a nice 36 psi. Got the car running, missing bad found out some injectors were not firing, got that all sorted out all injectors are firing. Start her up and when she gets warm starts to bog out and sometimes backfires when I give it throttle. Eventually it kills itself. So started checking everything per FSM and Bible, replaced water temp sensor, took out the aux air valve and blocked off the ports. Still same. Took off cold start valve and put the fuel pressure gauge in between it and the rail and 36 psi and not stuck open. Disconnected it for now along with the aux air valve since its not on the car, it was bad.

So now i can start it runs pretty good, but when it warms up it falls on its face. When its doing it I can disconnect the water temp sensor and it will instantly idle better but after a bit under load it will start doing same thing. Since I'm getting the right fuel pressure and I can feel the FPR working I would assume its good, although when I pinch the return line nothing changes. I know its running rich because the plugs are sooty and wet, I just had to replace them all cause they were fuel fouled and it wouldn't start anymore. I have also done all the continuity checks through the ECU and on the sensors themselves, on the temp and thermo sensor also checked the bullet connectors and they are ok. Guy at work with same car put my AFM on his car it worked good, and all those tests check out so its not that. Tested the TPS sensor and tests out, checked to see if its adjusted right and it is. I did notice that on the bottom of the EGR tube to the manifold there is a leak coming from it, gotta replace that but shouldn't think it would cause it to be rich. I'm just stumped, maybe I'm not reading carefully enough but I broke down and posted. Any help would be appreciated sorry for the long post. Thanks.

[jonathanrussell]

Check for leaks in big rubber air hose connecting afm and throtle body.

Still, sounds like afm to me but it sounds like you are sure your afm is good. When my afm was bad, my car was running rich and backfiring. It was the flap inside the afm getting stuck open.

[skunkteeth]

I went through a problem that I thought was fuel but was actually spark. At about 2000 rpms the car would shudder and shake violently, except when I had my old alternator in. I put a high output alternator in, and that is when the shakiness started.

I had a bad ground on my new alternator, and the car would be fine because of the voltage drop with the headlights on. Fixed the ground then it was always bad even with the headlights on. I figured it was the coil, and it was. Replaced it and all the stuttering is gone, and my mileage went from 14 to 20 mpg. You might just want to check the coil but Im sure someone will have better advice.

[fixxor]

I have checked the boots and they seem to be good. When I would disconnect the AFM it would run better except for at idle, where it would like surge but I think thats just a default safe mode. The flap opens smoothly. I will have to check the coil and grounds, thank you.

[fixxor]

I have checked the boots and they seem to be good. When I would disconnect the AFM it would run better except for at idle, where it would like surge but I think thats just a default safe mode. The flap opens smoothly. I will have to check the coil and grounds, thank you.

Update: Well today I tried some other things, still the same. Found out when pulling the plugs #3 stays clean, injector is ticking away and I'm getting spark. Great. Adjusted the AFM, seem to run a little better but when I try to drive it falls on its face. I'm lost.

[skunkteeth]

When you cleaned the gas tank did you replace the fuel filter?

[fixxor]

Yes, forgot to add that in there.

[jonathanrussell]

Could it be the fuel pressure regulator?

[fixxor]

Thought it might be, but it holds 36 psi, and there is no gas in the vacuum line when I pull it off.

[fixxor]

Ok, Well I finally figured it out. After adjusting the valves, checking timing today. I decided to leave the fuel gauge on car to test whats going on when I put some load on it and when it gets fully warmed up, previously I've just been checking it for a couple minutes then taking it off thinking everything is good. Not so. After its warm and I put load on it fuel pressure steadily drops down to 10 psi, now every time its done this the idle obviously has been getting bad so I would unplug the temp sensor and it would idle better so I did not think it was fuel pressure. Well I did it with the gauge on and it did the same thing only the fuel pressure did not go up it stayed at 10 psi....... so I'm kinda dumbfounded at that but in the end it would kill itself from lack of fuel, but I still wonder why my plugs were fouling, maybe just from idling so much. Anyways I'm glad I found the problem...

[sblake01]

Having put a new fuel pump on and the pressure regulator is okay although that's not really how you test it but it wouldn't regulate the pressure down to 10 psi anyway, I think you still have a problem with the tank. How did you clean it?

[fixxor]

Drained it, then pressure washed it with water seemed to get all the crap out. Got some fuel injector cleaner and let it sit in there a while washing it around and letting it sit in certain spots, then drained it all out and seemed to do a good job. Looked around and didn't see much of anything anymore at the bottom, but at the top there was still some rust, didn't think it was going anywhere though it wasn't much.