Bad PCM or ICM?

[NOT_aerosmith]

I was driving my car yesterday, and out of nowhere, it lost all of its power. I had to go wide open throttle just to keep moving and it still barely kept going.When I got back, I decided to pop the hood. I checked each injector to ensure that they were pulsing, each one was. I knew that the ignition wires and plugs (Napa Beldin and NGK TR55s) were fine since I replaced them about 3,000 miles ago.


I thought it was odd that the MIL light was not on. I then plugged in my scanner (Actron cp9185) and found NO codes. After that, I decided to observe the scan data values and compare them with the chart in my FSM. Everything on the scanner matched the chart in my FSM. I then made the assumption that something was obstructing exhaust flow; so I detached the exhaust from the rear manifold, started it up, and it ran exactly the same. As the car was running, I noticed that it had an abnormal amount of exhaust coming out, so I made the assumption that it was running rich. I then pulled out all of the spark plugs to find that the electrodes were black and the threads were slightly wet with fuel.

I pulled the coils off to check the primary and secondary windings, the resistance of the primary and secondary windings was the same for each coil. I also have spark. The motor does not run as if it is misfiring, but runs as if the injectors are dumping fuel into the cylinders. While the car was running, I unplugged some of the sensors to see if the PCM would throw codes, and it did.

I do not know what to do at this point. I am suspecting the PCM or ICM but I do not know. It would seem that the timing might be incorrect, which is impossible since the Ignition system is distributorless. Would a bad ICM cause this?

Maintenance I have done:
New 2.7 Bar FPR
New fuel pump
New fuel filter
New O2 sensor
New harmonic balancer

If you have any ideas, please help.
-Thanks

[sandrock]

It's completely possible the PCM is bad. 94/95 are flakey at best, totally useless at worst. I had a '94 that ran great when I sold it but had the exact same issues for the new owner about a month later. I suggested to him to change the computer, and it was right as rain afterwards.

The funny thing is...and Don (jrs3800) can vouch for this...the 94/95 PCMs fail hard and won't even say they've failed, even though there is a code for that.

[NOT_aerosmith]

Is there anything else that can determine a bad PCM?

[NOT_aerosmith]

If I get a remanufactured PCM, do I need to keep the PROM from the old one or will the reman come with it?

[Jrs3800]

If you get another one keep the PROM from your old one...

[NOT_aerosmith]

I pulled my PCM only to find that it is a remanufactured unit. I got another reman anyway, and replaced it. It still ran exactly the same. Is it possible that the PROM is bad?

[Jrs3800]

Dome a favor and check the ground buses on the passenger side of the car... If they are corroded clean them...

[NOT_aerosmith]

I checked the ground buses on the driver and passenger side; they were both clean. While the car was running I unplugged the MAF sensor, and it died. I can not get the car started now.

[crash93ssei]

What do you mean by "abnormal amount of exhaust coming out"?

Is your exhaust black, white, clear?
Have you checked your fuel pressure?
Compression test?

The threads on your spark plugs won't get wet with fuel, that wetness will be from oil sitting in the little valleys for the spark plug seeping into the threads as you remove them, not fuel from inside the combustion chamber.

Just because some parts are new, be careful not to completely rule them out as the trouble makers. Often times trouble that arises after a brand new part is installed is caused by a failure from that new part, so double check everything about the new parts, especially fuel pressure.


What specifically were you looking at comparing the values on your scantool to the chart on the FSM?

[NOT_aerosmith]

The exhaust is clear; it just shoots out at a high velocity.
When I pressed the schrader valve on the fuel rail, fuel sprayed out.

The fluid on my spark plugs smelled like gas. I took them out and cleaned them off, put them back in, cranked the engine some more and then removed the spark plugs again only to find them wet with gasoline.

The values I was comparing:

MAF gr/s
KR
O2 mV
TPS V
Fuel trim
IAT
IAC
Coolant temp
Loop status
Rich/Lean status
...and some other ones that I can't remember.

[crash93ssei]

Pressing the schrader valve and finding that fuel sprays out is not by any means an accurate way of testing fuel pressure, you need a gauge to verify the actual pressure in the system.

Clear exhaust doesn't indicate a rich condition, black exhaust would, and even at that point the exhaust would be very noticeably black before it caused an issue with power like you are talking about. I would rule out a rich condition if the exhaust isn't black at all.

Wetness on the electrodes can definitely be from fuel, but not likely on the threads.


I would look into fuel pressure test and compression test.