I FINALLY found a major problem with my car - HELP!!!

Bacondoggy

Registered User
ok since I have been baffled by what is wrong I took it to a knowledgable ford mechanic. He just called me back and this is the problem he found (he said there may be other problems, but this needs addressed first):

Whenever the car starts up, it is going into self-test mode. He checked the STI and STO circuts (for the wiring harness) and they are ok. But he thinks there is a problem with the PCM. He had it hooked up to the monitor and can see that the O2 sensors won't even switch on. So I guess I need a 91 SC or XR7 PCM (from a 5 speed). Anyone here have issues like this before? Lol - no wonder why the car drove like crap and missed and loped when it got warm! Also, anyone with ANY information where to get a 91 PCM, PLEASE either PM me or e-mail me (MarkGleeson82nd@gmail.com). I told him I would call him tomorrow and let him know if I could find any. I also have a paypal account if anyone is willing to part with one they know is a good part (I don't want to buy a PCM that may not work right)
Thanks guys for any help here!
 
I would also check the grounds on the back of the heads to make sure they are clean and tight and connected.
 
I'll mention that to the mechanic - I think I found a eec for $40 shipped so yay. New they are like $370. anywhere else there could be a problem with the ground? I think it could have gotten fried because when I bought the car it had one of those superchips in the eec, ecm, pcm or whatever you call it. If that went bad it could have messed up the eec - who knows? All I know is I removed it as soon as I saw it. Has anyone ever heard of a car forcing itself into self-test mode before? This guy said he has never seen it in the SC's before... he also said something about the FTI circuit (whatever that is) on the test connector, and that could be causing it if it was shorted... BAH! At least the #@$% thing is going to get fixed now...
 
Has anyone ever heard of a car forcing itself into self-test mode before?

No.

I think he meant it was in 'limp' mode, meaning some sort of failure forced the computer to go into a mode where timing advance is restricted, but things work well enough to drive the car to a repair shop. In this case, it can mean that the computer needs to be replaced.

Ken
 
well this is what I was told by someone over at tccoa:

"I had the exact same problem. What I did was run a new ground from the engine to the chassis on the passenger side of the car and from the battery to the chassis on the drivers side.

It was caused by a ground loop in the system.
What I did to diagnose the system was check for voltage differences at the sensor grounds. I found allot of fluctuation and the ecm only needs a 5 volt signal to go into self test mode."

so I guess it could be either case. I think what I will do is order an extra pcm, and also pass this information to the mechanic (without my car here, I don't know even if the heads are grounded)
 
The computer going into self test mode is from poor grounds causing voltage variations. There is nothing wrong with your computer. Run the ground wire like was said, and most likely it will fix your problem. Basically what happens is there may be up to .5V drop from the ground near the computer to the negative battery terminal. The computer works on lower voltages than everything else in the car, so that half-volt can be enough to throw the computer into self test mode, and if that happens while you are driving down the road, it will cause all sorts of weird drivability problems. I'm betting that your computer is actually perfectly fine.
 
For some reason people (DIYers and mechanics alike) seem to gravitate towards the "ECU/EEC/PCM is fried" conclusion. Sometimes they are right, but most of the time, it's another problem. The biggest thing to remember is that the EEC is just a computer: it does what it's told. If one or more of your key sensors are giving false readings, there's not much the EEC can do. Don't take this as a knock on your mechanic, but here are a few things I would check/clarify before replacing the EEC:

Find out if the car "stuck" in limp / failure mode or self test mode. There is a big difference. Limp mode is designed to get you off the road or to the shop. The EEC has detected a pretty major problem and is "limping" along. I don't know exact details but limp usually runs a very conservative timing map, lots of fuel and a very low rev limiter. A function of limp mode is that the car runs like crap! Self test mode is something entirely different. It is initiated by jumpering wires in the diagnostic connector (can't remember Fords' real name for it) and meant to test the function of the EEC and associated sensors. In self-test mode, the computer runs a series of tests and then spits out any resulting codes. If your car is really stuck in self test mode, then it is an easy diagnosis: either there are wiring problems or the EEC is fried. If the computer is in limp mode, then it's a little harder. I've seen bad computers stuck in limp mode, but that is pretty rare. It's much more likely that sensor / wiring problems are giving the computer bad info which is in turn putting it into limp mode. In that case, changing the computer won't do a thing.

The posts about grounds are on the money. Have your mechanic check / add grounds. A missing or bad ground will really screw things up.

Since your mechanic has a scanner, he should be able to easily see most sensor values. It should be pretty obvious if a bunch are way out of range. It is interesting that he mentioned the o2 sensors. I'm guessing that he means the sensors aren't switching (like they normally do). Did you by chance have you head gasket(s) go? Coolant kills the o2 sensors.

If you can get a known good EEC for $40, then it's a cheap thing to rule out. On the other hand, don't expect it to fix your problems.

Vince
 
Now its just an issue of finding the right PCM for my car. I was told by the mechanic (as well as another member) that 89-95 PCM's will "work" in my 91 car (as long as it is a 5-spd), but they wouldn't be right. Is this true as far as needing the right year/calibration for my car? (I can only use a 91 pcm?) This is what my mechanic gave me:

Calibration # 1 15 A RO

Engineering # F1WF 12A650 AA

Part # F1W8 (or y but it looks like an 8) 12A650 AB

Now this is what a guy with a 91 5-spd SC PCM sent me:
"my code on my 91 sc.....fosf-12a650-l2b..................LOE1 is the 4 code in caps that u also need" I assume LOE1 was what he thought the calibration code is/was, or did the mechanic give me the wrong one??? Are these interchangable? Is there a way to tell or find out what PCM's I can use?!?
ANY help here would be appriciated! Thanks guys!
:eek::confused::eek:;):confused::eek::D
 
L0E1 is only for the 89-90 cars, and was for the 5spds... without rewiring everything it will NOT fit your car.

You can run the U2Y/M2Y calibration which is the 5spd/auto for the 91 to 93 cars. The 94/95 calibrations will not work in your car unless you rewire everything.

So your 100% sure its the EEC that is causing your problems?

Frit
 
no, but if I could get one for $40 then I would buy one. the car is at a ford shop, and all I know is what I have stated in this message and what the mechanic has so far told me. I am getting really confused and starting to get pissed. He (mechanic) said he could get me a new PCM for like $370 and I was like f that. He told me the car itself keeps going into self-test mode, and the o2 sensors are not switching. So I printed him off this forum post when I went in and he gave me the calibration #'s I stated above. I don't care at this point. this car has never ran right since I bought it, rebuilt the engine (past 5 years) It has just sat around and I want it fized. Thats why I am paying money to have some guy look at it. I am so upset because this has gone on and has been over 5 years easy. I just want it fixed. I NEED a compatible PCM - he's waiting for one - lol
 
Why don't you try running that ground wire first? That won't cost you anything, and if it doesn't work, you are no worse off than when you started.
 
I had a 91 that was stuck in self test just as soon as you turned the key on. You could hear all the clicking of the relays and the fan would run on both speeds for a few seconds. Car ran like crap. Drove me nuts for a week. Here`s what I found. On the passanger side there is a set of wires that run just around the motor mount and someone had gotten them pinched in the motor mount itself and was grounding the proper wire for the self test. Check those wires out first. Its been awhile but as I recall it went to the knock sensor and the starter solinoid. After I got the wires unstuck and taped up it was all good and everything worked as it should. On a 92 I had the wires on the passanger side right next to the exhaust mainfold held in by a plastic thinggy had fallen down and were melting on the hot manifold. Bought it this way and man did it take alot to correct this problem. Not one blown fuse.
 
ok, first off, I can't do anything (like with grounds, etc.) because the car is and has been in the shop for about a week now. But I did show the mechanis a printout of this post, and he has been looking into the grounding issues. He didn't want to take the SC off, but he told me he "wasn't convinced there isn't a wiring problem". The more I think about it, the more I DON'T remember if I grounded the heads. He has tons of books open and was looking at all the wiring diagrams - do all SC's have BOTH the heads grounded, or did some just have one (pass. side)?

on to the EEC - still havent found one yet - I fount out for calibration codes
1-15a-ro
1-16a-ro

15 designates manual, 16 is auto... Anyone know about part number suffixes? Because mine is # F1WF 12A650 AA
I actually found (in Kansas of all places) a F1WF 12A650 AC

Will this work? From what my mechanic told me the part # for all the pcm's is the 12A650 but the suffixes before and after are what designate the different models. He wants me to stay away from the 89-90, and auto PCM'S, as they are different values. BUT what he said is the AA AB AC BA, etc at the end are different sowtware revisions. Can anyone verify this? I mean I assume its true - and if it is, the "F1WF 12A650 AC" SHOULD work in my car.... right? I know that is from a 1992 5-spd SC... OH WHAT A HEADACHE
 
new stuff - yay

ok I ordered a PCM for $85 from a 92 5-speed, but I also found out aomething else that was wrong... The one (I bought 2 new o2 sensors) must have been bad from the box, because it was shorting everything out. He replaced it with a new one, and he says the car runs ALOT better (he still hasen't driven it), but there is still a problem with the sti (self test input) circuit. He wants to make sure its not the pcm, since the voltage is still fluctuating on the circuit (I keep asking him about the grounds and I forgot to ask him the last time, so I dunno about that but he is definatly aware of that). I didn't know whis, but he said the O2 sensors are actually tied into the PCM, and with the sensor shorted out, could have damaged the PCM by either the short itself, or even by voltage bleeding back into the pcm through the sensor. Well at least my car is getting fixed!

Anyone know where to get a pair of cheap used (blown out, or I can clear them out) aftermarket cats that will fit 2 1/4" exhaust? my zip is 17356 - I prefer aftermarket ones, as my exhaust is custom... Thanks guys! Hopefully I will get my car back soon, and this wouldn't cost me tons of $$$
 
The O2 sensor is tied into the PCM. I don't know if a shorted one would cause it to run poorly or fry the PCM in an SC, but I can tell you that it happens a lot on late 90s chryslers, and sometimes with them, the car will come in and won't start at all, then if you unplug the O2 sensor, it starts right up and runs perfect. Since you already ordered the PCM, you might as well throw it in there and see what happens. Maybe it will help, maybe it won't.

As for the high flow cats,
http://cgi.ebay.com/ebaymotors/2-25...025QQitemZ380017860483QQrdZ1QQsspagenameZWDVW

I've used this style on all my cars that I replaced the cats on, and I've never had a problem with it. Plus they are high flow, cheap, and small enough to make fitting them easier.
 
what I have gethered is that here in PA, is our emissions testing for a 1991 is a visual inspection only. so I just want "cats" that ARE hollowed out, or ones I can easily hollow out myself and will weld right up to a 2.25 front, and would have no clearance issues
 
Back
Top