Car stalling any advice appreciated

[drewcole5150]

Hello, I have a 1985 Nissan 300zx Base non-turbo. I've been having the same issue for a while with no luck. The car will start, idle up as normal, and then try to die. If I press the accelerate, this only makes it worst. Idles good for a few seconds then rough idles down to a stall. Put it in gear let off the clutch with a little throttle also dies. I replaced the MAF, ignition coil, CAS, plugs, wires, tested all fuel injectors and fuel pump. I have resistance from all sensors and Injectors, all fusible links replaced and tested. I have also pulled the fuel rail to see if any injectors are stuck open. Non are. I did this because the oil reeks of gas. An thing I have noticed is that when ever I open the distributor cap that the rotor is still in the same position as before. I'm not much of a mechanic so any advice and suggestions are highly appreciated! Also going to try a compression test next weekend.

[Z_Karma]

Pull the vacuum line going to the top of the fuel pressure regulator. There is a diaphragm inside that regulates the fuel pressure. If you smell fuel, that means that the diaphragm is bad and raw fuel is getting sucked into the intake plenum through that vacuum line.

[drewcole5150]

Sorry I failed to mention that I replaced the fuel pressure regulator also. I replaced most vacuum lines I could locate when I removed the plenum and fuel rail the first time around. It was fairly corroded before replacing!

[drewcole5150]

I do notice a hissing sound when the key is on and the pump is priming but I can't locate what may be causing it. (Hear it in the engine bay closest to the 2nd injector)

[JSM]

Sorry I failed to mention that I replaced the fuel pressure regulator also. I replaced most vacuum lines I could locate when I removed the plenum and fuel rail the first time around. It was fairly corroded before replacing!

So oil still smells of gas after FPR replacement.

[drewcole5150]

Yes, this past weekend I did the pressure regulator while checking the injectors for leaks. I replaced all the vacuum and fuel lines too. (They came with the regulator) i changed the oil and filter again for a fresh start. After a few failed attempts at holding an idle I could smell faint odor of gas in the oil as before the attempts I could not sense any smell from the fresh oil change.

[JSM]

IM wondering if your return to your tank is clogged for some reason causing excessive pressure on the rail?

[drewcole5150]

I will need to look into this also. Know of any fuel line diagrams for this car? Thanks for the reply!

[z31_chris]

My car sounds very similar to yours, the issue for mine was there was carbon on the distributor
caps, just use a metal wire brush.

[JSM]

My car sounds very similar to yours, the issue for mine was there was carbon on the distributor
caps, just use a metal wire brush.

That caused excessive fuel in the oil?

[z31_chris]

That caused excessive fuel in the oil?

No it didn't burn all the fuel and there was a lot of white smoke coming out and the smell of gas.

[drewcole5150]

Update: I opened the ECU and found a few burned resistors and some broken connections on the circuit board. Should have a replacement ECU in by next weekend. As for the distributor caps they are clean. This next weekend going to hook up the new ECU with a new oxygen sensor just in case (since I haven't replaced it either). Will post an update on these replacements.

[jy1235689]

Just fyi I had this issue and 2 things, separate, contributed to it:
1. I had an injector harness short to ground, ever so slightly, that one whole bank was still clicking but not opening enough to put out any fuel. Ran on 3 basically and any throttle killed it.
2. ECCS (ECU) had water damage. Replaced it.

I went through the charade of testing all the sensors when car was on and off according to fsm, and replacing them all in doubt. Only made it seem better but didn't solve the above. I didn't think it was the harness at first because I did the clicking test on each injector and they all sounded like they were firing. 6 months later, frustrated and relieved, I pulled on the harness and it got rid of the short and started running perfect.

Praise God!

Edit: I forgot to mention that O2 sensor, maf, and the majority of the sensors didn't make a lick of difference in whether it was "able to run" plugged in or unplugged. all they do is help it run smoothly and correctly. And my fuel smelled like pure gas too and hasn't since changed it and fixes above. The bad ecu was keeping the fuel pump on while the car was off too, which is irony that it would have too much gas while off and too little while on.

[drewcole5150]

Just fyi I had this issue and 2 things, separate, contributed to it:
1. I had an injector harness short to ground, ever so slightly, that one whole bank was still clicking but not opening enough to put out any fuel. Ran on 3 basically and any throttle killed it.
2. ECCS (ECU) had water damage. Replaced it.

I went through the charade of testing all the sensors when car was on and off according to fsm, and replacing them all in doubt. Only made it seem better but didn't solve the above. I didn't think it was the harness at first because I did the clicking test on each injector and they all sounded like they were firing. 6 months later, frustrated and relieved, I pulled on the harness and it got rid of the short and started running perfect.

Praise God!

Edit: I forgot to mention that O2 sensor, maf, and the majority of the sensors didn't make a lick of difference in whether it was "able to run" plugged in or unplugged. all they do is help it run smoothly and correctly. And my fuel smelled like pure gas too and hasn't since changed it and fixes above. The bad ecu was keeping the fuel pump on while the car was off too, which is irony that it would have too much gas while off and too little while on.

Thank you for the reply! I'm still waiting for the ECU to be delivered but have not tried to adjust the fuel injectors wiring harness. Also how did you permanently fix this issue with the wiring?

[jy1235689]

Buy new harnesses and wire them in. For now though, I have the #1 injector wire pulled tight so the wires don't short. I don't drive the car much and just fixed it 2 weeks ago.

[drewcole5150]

Thank you!

[drewcole5150]

Update: New ECU in the car now, idles smooth with the occasional misfire. Still bogs down and tries to die when hitting the throttle. i pulled the wiring harness for the injectors up tight and tried to check for the short you were talking about but not sure if that made any change. It would rev up great but then the next attempt not so much. Back and forth like this. Holds idle now for the first time in a very long time.

[jy1235689]

Keep us updated. I'm going to need new harnesses because mine keeps going back into the state yours is in.