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'88 GT ECM troubles

Long story short: My mechanic that I trust with everything had my Mustang for 8 days to replace the heater core and try to track down a backfiring and stumbling problem. After fixing the heater core, replacing two cracked spark plugs, fixing a leaky upper to lower plenum gasket and checking every sensor on the vehicle he gave up and said that it must be the computer. He did everything that his diagnostics equipment would let him do plus brain-stormed with a mechanic from a dealership. The car still takes 4 turns of the key to get it started when cold and backfires whenever she feels like it. I hate to buy a new computer not knowing if that will fix it. Has anyone dealt with Route 250 Auto in Ohio? Seems to be a reputable used parts dealer.

Thanks for your input, Gary

Reply to
Gary Nichols
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Sounds like the TFI module on the distributor to me. If it's the original from '88, your lucky it lasted this long. That's most likely the culprit and is much cheaper than replacing a computer.

Reply to
Mike King

Thanks Mike. I replaced the original a month ago. I put a layer of goop on the back to gaurd against heat failure. I don't remember the TFI making my car run rich like it's doing now. I'll keep it in mind before I buy a computer, though.

Gary

Reply to
Gary Nichols

Wait, running rich and hard to start? Have you checked your fuel pressure? The regulator or pressure sensor could be the problem then.

Reply to
Mike King

Fuel pump wasn't holding pressure so a new one was installed along with a new regulator. I left a lot of 'new' stuff out in my original post to try and keep it short. Keep trying. You'll fix my 'Stang eventually. LOL

Reply to
Gary Nichols

OK, next thing that would cause a rich mixture would be O2 sensors or MAF... Also check that the TPS is set to .99v or less at closed throttle.

Reply to
Mike King

Oops, oh yea, '88 non CA means no MAF, I guess it's not that...

Reply to
Mike King

All sensors have either been replaced in the past month and/or verified working properly. That's why I feel my only option is a new ECM. I just wonder why the ?%$# thing won't throw a code. If I wasn't bald I'd have two fists full of hair right now!

Gary

Reply to
Gary Nichols

I'd have a real problem convincing myself that an EECIV PCM could give me a backfire concern (we're talking into the intake?). Coil, cap, rotor, wires..... a module that doesn't give enough dwell can do it too.... I'd recommend going beyond the sensors and get right back to the base engine and tune up...

-- Jim Warman snipped-for-privacy@telusplanet.net

Reply to
Jim Warman

Sounds like the ECM is in Limp In mode. i.e. it's toast. Limp in locks the injectors full rich and locks timing at 10 degrees. It won't throw a code because you can't get it to go into test mode. I had a faulty diagnostic machine blow my first ECM, and then managed to blow a second one when I tried putting it into self test mode out of sequence. I currently have the Cobra fuel system upgrade in my car (complete with ECM) which I try my best never to touch and then only with a code reader.

Reply to
Ironrod

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