95 LeSabre Hesitates And Stalls Suddenly - Electrical/Computer Problem?

[CarDude225]

95 LeSabre, 79k mi

The wife was driving along today and all was fine until suddenly the car began to misfire/hesistate, and then at an idle it would stall out.

I looked at the car tonight and indeed it is running horribly. Sounds like it is running on 2-4 cylinders at any given time. I ran the car in the garage and it stalled itself out, then I noticed something very strange; the fuel pump relay clicked on and off in unison with the fuel pump, seemingly randomly. It did this for about 10-20 seconds, then the cooling fan came on for about 10-20 seconds and went off. I started the car again and it stalled out shortly after, then the same thing happened with the fuel pump and cooling fan.

Thinking I could "reset" the computer, I disconnected the battery cable for about a minute, turned on and then off the ignition, then hooked up the bat cable again. Started the car. It ran perfect for about 15 seconds so I thought the problem was gone, but then it started having fits again and stalled out. Then the fuel pump and cooling fan anomaly happened again.

I checked and reseated all fuses from both the under-hood panel and the under-steering wheel panel: No fuses were blown and the problem persists.

About 3 mos ago the car was running a bit rough (not like this though), and after determining that the 3-6 coil pack was producing a very weak spark, I replaced that coil pack, and the car ran perfect again. However, I am concerned that the way I tested the coil packs may have damaged them; I pulled the plug wires off of the coil packs one at a time and allowed the spark to jump between the coil pack stud and the side of the coil pack. I did this for all 3 coil packs. I just learned that this may have damaged the coil packs. However this does not explain the odd electrical behavior of the fuel pump and cooling fan.

As a side note, my Ford Crown Vic had a very strange problem once. Suddenly the transmission would shift wildly, then it would be fine, then randomly it would shift wildly again, and a ton of troubleshooting was done (months) before the only possible item was left to replace - the COMPUTER. That fixed it.

I suspect the computer in my 95 LeSabre may have become faulty but I have not ruled out the other coil packs.

Opinions please...thank you!

[brcidd]

Do the tap test on the PCM...I had a '95 Park Ave (same car as yours) that acted strange like yours. The fuel pump relay would start chattering for no reason and car would stall.. and everytime I tapped on the computer, the car would die. Replaced computer and all was fine after that. PCM is behind glove box.

[CarDude225]

OK I had a weird anomaly occur - the key suddenly would not activate dash lights or crank the engine. I must have accidentally left the ign fuse out or lost it (weird), because I plugged the spare into the ign fuse hole and everything lit up. Wrong size fuse though. I don't get what I did wrong. I have easily corrected this apparent mistake. But anyway, back to the main problem...

I pulled what I believe to be the PCM out from behind the glove box. The box I pulled has connectors colored red, white, and blue. Is this the PCM? I pulled all 3 plugs out and put the box on the bench and opened it up. It looks clean inside with a layor of clear seemingly protectant film on everything. I put it all back together and plugged it in and started the car. It ran differently; It seemd like it was running rich, but mostly steady. The exhaust smelled potent. Then I realized the car was getting very hot. Also the alternator light was on the whole time, and I confirmed the battery was not receiving a charge. I had my battery charger on it at the same time to help maintain some voltage and it held around 11.9v. Then I noticed the Temp light was on. Fearing I was allowing the car to overheat I shut it off quick. The cooling fans never came on. There was a small amount of smoke coming off the front of the exhaust manifold where I think some oil gunk had settled prior.

Also while the car was running I banged on this box to see if it had an effect on engine operation: it did not. I shut the car off, then started it up again, and it ran poorly and stalled.

The box which I suspect is the PCM has these codes on it:
SERV.NO. 16183247 BMYU
*86BMYUM743268KGV*
16211694
Inside the box there is a module that plugs into the board. The writing on this module is as follows:
BMYU
1621
1712

I see based on some reading tha the PCM controls whether the alternator charges or not.

Is this screaming PCM problem or what? I am considering searching for a used PCM. Is it simply a matter of matching up PCM part numbers to replace the PCM? Which numbers have to be matched? Also do I have to be concerned with flash/firmware versions too, and what about the module that plugs into the board of the PCM (what is that called) - Do I have to replace that separately or does that plug-in module typically come with a replacement PCM?

[brcidd]

I really hesitated to change the PCM on mine..was looking for some one I knew that had the same body style car- so I could temporarily swap PCMs- to see if it made a difference-- but finally just grew fed up with it and replaced the PCM with one I bought new from Autozone. I did. though, have ignition module checked first, and I put a test light on ignition switch hots, and swapped out coils before deciding to go with the PCM change....The FP relay chattering was pretty strong evidence, even after I swapped out FP relay.

[Jrs3800]

The 94-95 3800 V6 failures are common... You sound like you are describing a PCM failure...

I went through 4 or 5 of these on my 95 Bonneville as I could never get a Reman that was quite right... Finally got pissed and a buddy rewired it for OBD2 using a 97 PCM...

This failure is extremely common on these cars...

If you can scan the PCM you might even get a code 1361( some scanners show it as 361 )

[CarDude225]

I've ordered a Cordone reman PCM from Autozone $99 / 1yr warranty. I believe it does not come with a PROM module so I will likely be swapping that. Hopefully it is not the PROM module that went bad.

JRS, it is discouraging to hear that your multiple remans were never right.

My other option is to purchase used from salvage / Ebay.

[brcidd]

Just take your PCM with you when you get the new one- they will open yours up and swap the PROMs- and they will want your old PCM for a rediculous core charge of over $100!! And you will probably pay tax on the core charge- depending on your state tax laws- what a PITA..At least you'll have a warranty- unlike ebay or a boneyard...

You have the percentages on your side--like was said above- these model years were known for PCM failures.

[Jrs3800]

Originally Posted by CarDude225

I've ordered a reman PCM from Autozone $99 / 1yr warranty. I believe it does not come with a PROM module so I will likely be swapping that. Hopefully it is not the PROM module that went bad.

JRS, it is discouraging to hear that your multiple remans were never right.

My other option is to purchase used from salvage / Ebay.

Yeah, it was never a good situation..But I learned quickly how to spot a failure coming... I loved the car too much so when I would pack the car for a long trip a known good PCM( One I tested for a couple of weeks) would go into the trunk as a spare.. This way if I ever had any issue I could just pull over and swap... Good thing is it never happened that way...

I have a stack of bad 94-95 PCM's... My 95 Pontiac Trans Sport with the 3800 had the same odd failure... Would do something funky and then would stall out... Sometimes it wouldn't start... Installed another and it always started and always ran, but would always idle really funky... I drove it that way until I did my engine swap... At that point my Buddy again wired me up for OBD2 using a 1997 PCM... I have had 0 failures and have the ability to tune or Flash the PCM when I need to make changes...

The one year warranty I like, you made a good choice there... I can't promise thats the problem, but with everything you have described, thats exactly what I would be looking at..

Let us know how it works out..

[CarDude225]

Well gents guess what? I rcvd the reman PCM, put in my original PROM, installed the PCM back to the car, and viola, problem completely solved!!! It did start real hard the first time, but I assume the new PCM had to "learn" for a minute or two.

Thanks everyone for your help. What a PITA but a pretty quick diagnosis, easy fix, and the price tag wasn't too bad either. Too bad so many failures on the 94-95 PCMs.

[Jrs3800]

Glad to hear that did the trick... Extremely common... But when it runs right its really right...

Just Curious what part of FL your in? Space Coast here... We had a Meet in November for H Body cars... But we always get LeSabres, Chevy trucks and Bonneville( Supposed to be a Bonneville meet )... One year the Chevy Trucks ruled...LOL

Glad to hear the car is running well again...

[CarDude225]

SW FL - Ft. Myers.

[Jrs3800]

Small world in a sort I guess...lol

I will assume the car is still running like a champ... and the 95 Tuned Port 3800 is an odd duck in a really good way.... And was the only year the L27 was built with some series II parts...