92 SC running rough, chasing codes in circles!

BenG

Registered User
92 SC started running rough and losing power when it hit about 45mph, The engine quickly deteriorated to where it ran rough all the time and would barely idle, sometimes dies at idle. CK engine light stays on.

We got codes and it said coil #3 failure. We replaced the coil pack with no improvement, so we went forward with replacing all the plugs and wires, too. Still no joy. Checked codes again, the previous one cleared , but it said MAF , so we replaced the mass air flow sensor and the mass air pressure module. Still no joy. Checked codes again and the previous ones cleared, but it gave codes for one O2 sensors and coil #3 again so we replaced the O2 sensor. Still no joy; but the coil code cleared and It then gave code for other O2 sensor, so we replaced it,too. Still no joy. Checked codes again and it still says one o2 sensor is bad and that it now can't get sufficient rpm change for tests.

I feel like we are just chasing codes around. We have checked vacuum lines and wiggled connectors over and over again looking for a problem, but just can't seem to track it down. However, it is interesting to note that as soon as I hit the "test" button on the code reader, the engine levels out nice and smooth. When it finishes testing, it goes back to running lousy.
Every now and then on the road, it will suddenly start running right for just a minute or two then go right back to limp mode.

Has anyone here solved a similar problem? Help!
 
Sounds like a possible bad engine and/or engine sensor ground. The main computer ground is that extra wire that attaches to the negative battery cable, is that still connected? There are others as well but that would be one of my first guesses. Check all ground circuits. Do you have a schematic?
 
Thank you; that is one thing we have not checked. I do have schematics and will start looking them over today.

My son bought this car about six months ago from a professional mechanic. It looked and ran great, but quickly problems emerged. Cracked fuel pump, leaking trans fluid, oil leak, leaking radiator and cracked reservoir, exhaust leak, now this... Was this an incompetent mechanic or is this just what life is like with an old T-bird? I'm trying to decide if we put more money into repairing this car or cut our losses and dump it.
 
Pretty sure CEL codes dont tell you if a sensor is bad or not it just gives you a fault that needs to be looked into...if an O2 sensor codes pops up, that doesnt mean the sensor is bad necessarily, it could mean that it is reading insufficient AFR. You should be testing the MAF and the Coil and the O2 before just replacing them

As for your problem...most intermittent problems such as this happen from bad grounds...and usually the ECM or the DIS Module cause this...I had a 91 auto that did this and it happened to be a bad ground where the DIS mounts to the Jackshaft bracket...it needs to have sufficient dielectric grease underneath it
 
MY 91 auto that I had was exactly like that...It had a tranny rebuild first, then a master cylinder rebuild, then head gaskets....I eventually dropped around $10K and thats when I said I need to start working on cars myself if I want a SC and I sold the auto and found a low mileage 91 5-speed
 
Most SC's have not been maintained properly over the years and hence you tend to end up with a basket of broken eggs. That being said, if properly maintained I don't see the SC as having excessive problems. I've owned them since 1990 and currently maintain a fleet of them. It's not too bad and they are really quite reliable, even for daily year-round use.

But overcoming the neglect of a previous owner can be a bit tiring. Resist the urge to dump a lot of money into the car as it probably doesn't need it.

For example, many people have spent $1500 replacing ABS components only to realize after awhile that it was a bad relay, or some other minor component.

Don't overlook the cooling system though as Ford 3.8's are all known for head gasket issues if not properly maintained.
 
Dont get me wrong...I love my SC and like Dave said by finding one that has been properly maintained and driven regularly, I wouldn't hesitate to drive it across country

I am not one to give up but sometimes you do need to just cut your losses

good luck
 
Pretty sure CEL codes dont tell you if a sensor is bad or not it just gives you a fault that needs to be looked into...if an O2 sensor codes pops up, that doesnt mean the sensor is bad necessarily, it could mean that it is reading insufficient AFR. You should be testing the MAF and the Coil and the O2 before just replacing them

Yes, you are absolutely right; thank you for pointing that out. Since it ran fine with the tester hooked up, and intermittently ran fine, I guess I assumed that there was no "real" malfunction but just a bad sensor or electronic part somewhere. Not always a safe assumption, and not a good diagnostic process to just replace sensors without verifying if they're really bad. Again, thanks for making a good point.
 
Fixed!

While we were having this discussion, my son replaced the DIS (as you indicated might be the issue) and that fixed it! It's back to running normally now. You folks hit it right on the head- nice!

I'm still a little worried about this car, but I"m glad to hear that some of you have had good overall luck with reliability. For now, at least my son is very happy that his ride is back in action.

Many thanks for your insights!



Note added later: I checked the old DIS and it is bone dry on the bottom- it was probably a grounding issue just as you guys originally said. It would be interesting to put the gel on the bottom and reinstall it. Fortunately, he didn't lay out any hard cash for the DIS; he got it from a friend who blew his engine racing his SC (also a 92).
 
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While we were having this discussion, my son replaced the DIS (as you indicated might be the issue) and that fixed it! It's back to running normally now. You folks hit it right on the head- nice!

I'm still a little worried about this car, but I"m glad to hear that some of you have had good overall luck with reliability. For now, at least my son is very happy that his ride is back in action.

Many thanks for your insights!



Note added later: I checked the old DIS and it is bone dry on the bottom- it was probably a grounding issue just as you guys originally said. It would be interesting to put the gel on the bottom and reinstall it. Fortunately, he didn't lay out any hard cash for the DIS; he got it from a friend who blew his engine racing his SC (also a 92).

The stuff you are supposed to put on the bottom of the DIS module is intended to help transfer heat from the DIS module into the aluminum accessory bracket it's bolted to. It is grounded through the 4 mounting screws.

David
 
Thanks guys!!!

Today on my way home my car made a wierd sound and the car stalled a bit. At first I thought I was imagining things but the car felt a bit weird. I was going about 45 mph and when I slowed down and stopped at the light the car was idling really bad almost shuting off. I was stalling in 1st gear but then 2nd and third were not that bad.

I barely made it home and was dreading a blown head gasket but I wasn't getting white exhaust out the back like I did when the head gasket blew on me a few years back.

I got home did a search and this is the first thread I read. I went and bought a DIS at autozone slapped it in and good as new again.

Man this has really saved me cause my 92 5 speed is my daily driver and I was dreading the worst.

Thanks again for everyones input this forum has saved me many times.

Stay Safe and enjoy your rides,
LoneStar
ATX512
 
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