One last try

[2.3Lxhatch311]

I know I've posted this problem more than once. And I know that so far no one has had any ideas I haven't already tried. But here we go, one last time.
My car has a serious air fuel mixture problem. At idle, it blows large clouds of both black and white smoke. Throughout the driving range, the vehicle sputters profusely. Pushing the accelerator to the floor negates the problem. The vehicle consumes extremely large amounts of fuel. If the throttle position sensor is unplugged, the car performs nominally throughout the driving range. However, it runs extremely rich without the sensor connected. When I replaced the computer, the car ran perfect for 10 minutes. But after shutting the car off, it later went back to running exactly like it had before. But during those 10 minutes, it behaved perfectly. So, my current thesis is that the wiring from the ECM is at fault. What I need to know is, how comprehensive is that harness? Do I have to rewire the entire vehicle to fix this? 1987 Mustang LX hatch, 2.3 N/A. Is it likely that the wiring to the air fuel mixture circut is faulty, and that that circut is being burned out by the malfunction? Every sensor is brand new, and are all in working order. This problem is a conundrum for me, and every mechanic I've talked to about it.

 

[Keasbey]

have you taken the codes?

Have you any vacuum leaks?

Maybe the thing with the computer is only because your computer haven't detected everything for the 10 first minutes of driving, and then see every information the sensors is sending to him and then adjust itself in function of all the informations..

 

[2.3Lxhatch311]

It gave a code for the TPS even though the TPS functions normally. It reads .99 at idle like it should, and reads 4 volts at WOT, like it should. It also throws a couple other things that i expected, like the EGR, the clutch position sensor, and other suched negated parts of the car. The parts that manage air fuel mixture are all working like they should, I don't know why it threw a TPS code, because the TPS works. That's why I think it's an electrical problem. Yes, there is a small vaccum leak. just enough for the engine to idle off of. I've not yet been able to determine it's location, but I don't think that's what's causing this. I've had cars that had TERRIBLE vacuum leaks and all they ever did wrong was Idle high. I wouldn't be so sure if it werent for the fact that unplugging the O2 stops the sputtering. I think that is the one fact we should all pay close attention to. Why would unplugging the sensor make it run more stabily, while at the same time running even richer?

 

[Keasbey]

Mine was rolling ****ing rich, and then I changed all the gasket between my lower intake and my airbox, and all my problem of unsteady idle, rolling rich was solved...

If it's an electrical problem, try to find an electrical plan of the harness, where the TPS wires is connected on the computer and look how much voltage the computer receive..

Clutch position sensor code is normal (67 if I remember well)

Did you clean the "hole" in the throttle body for the EGR? maybe it is full of carbon deposit, and the computer read something anormal?

 

[1fastfox]

GT350R has the voltage readout for many important sensors on his website. search for it here or on turboford.org cause i cant remember the address.

patrick

 

[RustBucket]

If it's throwing a code pertaining to the TPS and the TPS is working according to test procedures, then the ECM isn't seeing what you see with the voltmeter at the TPS. I'm with Keasby on the thought of checking TPS feed at the ECM.

If I've read correctly, two different ECM's have thrown the same fault with everything else the same. It does sound like a wiring issue. The odd part is that pig rich would mean the ECM is seeing TPS return voltage higher than actual. Ya got me on that one. I'd still like to see what shows up on the TPS signal pin at the computer though.

 

[bhuff30]

did you check the fuel pressure regulator hose for gas in that vacume line? Did you check the fuel pressure? Pull the plugs... if one is black and the others are fine then it might be a bad injector.

 

[2.3Lxhatch311]

Regulator has been replaced. So have the plugs. However due to the rich nature, the plugs become clogged with soot very quickly. I was considering yesterday replacing all the intake gaskets to see if that helps. I did that when I rebuilt the motor, but hey, maybe I didn't lubricate one of them properly. I will definatley find out which pin is for the TPS on the ECM, and test it's input. Perhaps it is meeting up with another wire somewhere along the way and recieving some extra current. However, that seems a little unlikely. I think there is a dead short in one of the air/fuel mixture wiring circuts which causes damage to the ROM chip that determines fuel trim.

 

[JB66]

Pull the SPOUT out of the connector to put it in closed loop and see how it runs.

 

[140CILX-Coupe]

What I would do is get a turbo motor,ecu, vam, harness and start a turbo swap....

 

[Touring23]

2.3Lxhatch311, I missed what year your car is. On my '93, my ECT connector corroded to the point of an open circuit. This told the computer the engine was very cold, hence go to cold start enrichment even though the engine was fully warmed and ambient air temps were >90*. Same symptoms, and no codes because the computer was doing what it should. The IAT might cause the same problem, I don't know.
Hope this helps. It's an easy fix.

 

[2.3Lxhatch311]

2.3Lxhatch311, I missed what year your car is. On my '93, my ECT connector corroded to the point of an open circuit. This told the computer the engine was very cold, hence go to cold start enrichment even though the engine was fully warmed and ambient air temps were >90*. Same symptoms, and no codes because the computer was doing what it should. The IAT might cause the same problem, I don't know.
Hope this helps. It's an easy fix.

I'll check it out, but I don't know. I replaced that sensor and it started reading for the first time. I don't think theres a fault there. I already replaced the intake air temperature sensor.

 

[youknowit62300]

o2

You said if you unplug the o2 sensor it runs normal? have you tried replacing that? or what about your cat(s) if they are clogged the vehicle will do lots of weird stuff. I would look at that but also find out what pin the tps is and splice in a temp wire run it from the tps to the computer and it that solves it then you know where the problem lies.