I've been fighting this for months and I'm burned out. I remember the guys here being incredible with electronics so this is my last ditch effort. The local Ford gurus don't have a clue what to try next. I'm hoping you guys can help me out here.

I have a 1990 Crown Victoria station wagon with an EEC-IV ECM. The electronics are pretty well identical to the SD-based Mustangs.

A few months ago it started falling on its face if I gave more than slight throttle after about 40 minutes of driving. It progressively worsened to the point I couldn't take it any more. Here's what I've found:

KOEO:
TPS REF is getting 4.98v
TPS SIG is getting .15v at idle, 1.35v at WOT

Great, bad TPS. Swapped it. Twice. Same thing.

I'm getting zero resistance from sensor to ECM plug for both "hot" wires on TPS.

I swapped to a 1990 Mark VII (HO) ECM, just to see if it was my ECM because the electronics are the same... but it's doing the same thing still.

Is there anything that could be triggering the ECM into some sort of limp mode where it's going to shut down potential TPS input? I'm completely stumped. I've worked on it a little bit here and there in my spare time but I'm tired of it. I'm ready to fix it and sell it so I can order new suspension stuff for my new 4v 5.0.

Here's the car in question:



It's clean and was running perfectly and getting 22mpg, but that's all gone, now... and I just can't trust it enough even as a beater car any more. Help!

Trouble codes:

KOEO:

87- Primary Fuel Pump Circuit Failure
11- System Pass

KOER:

12- RPM Not Within Self Test Upper Limit (I lost the seal to my cruise control servo and didn't seal it properly)
21- Engine Coolant Temperature (ECT) Sensor Out Of Self Test Range (Engine was cold; would that cause this?)
95- Fuel Pump Circuit Open-PCM To Motor Ground (WTF?)
44- Secondary Air System Inoperative (I cut the belt to my smog pump)
33- EGR Valve Opening Not Detected
13- RPM Not Within Self Test Lower Limit (Again on the cruise control servo)
74- Brake On/Off Circuit Open–Not During Self Test

Does any of this help diagnose anything at all?

odd that no TPS codes came up . i would first double check the TPS signal voltage and recheck the codes. with 5v in and only .15v out at closed throttle there should be a code corresponding to that problem. did you check continuity between the SigRTN and a good ground (with key out engine off)? should be negligible resistance.

the ECT code may be because the engine wasn't warmed up, but it's summer time so that shouldn't be the problem there. might want to check this thread out: viewtopic.php?f=26&t=217

also this thread regarding the fuel pump circuit: viewtopic.php?f=26&t=553


the rest of the codes shouldn't be a problem for now. focus on the TPS issue first

Thanks for the reply. I'm getting 5v at the orange wire. Running a designated ground straight from TPS to chassis makes no difference. Otherwise I don't know how I'd test, as I've never diagnosed an electrical problem like this before. The only reason I'm tackling it is I have a lot invested in this car but if it's not at least running I'd just as well throw it away.

sounds like you're on the right track. might verify your results with another meter and recheck for a code 23 (TPS out of self-test range) or 63 (TPS below minimum voltage).

some extra reading in this thread: viewtopic.php?f=26&t=373