Evil Drew M

First off I have read countless discussions regarding the known ECM issue these have where the vehicle will just die for no reason and then take some effort to get started. In this case the issue centers around the harness to ECM interface and the pins.

However I do not believe this to be that issue and I will explain why shortly.

Basics:

• EARLY 1997 ZJ (12/96 Prod. Date)
• 4.0L
• Auto

The vehicle will randomly stumble while driving. It has been doing this for several weeks. It has only actually died once and that was the other day. Usually it dies for a second and then fires again by itself without any major loss in speed.

When I first looked at it there was a P0351 coil code. At that point I did the research on the stalling issue. The owner opted to replace the coil and see what it did.

It is back with me now and there are NO codes, either stored or pending. I do not believe it to be the mysterious ECM issue because one of the tell-tale "checks" for that is to tap the ECM and/or wiggle the plugs with the engine running to get a stall. When I do that it doesn't even flinch. I feel like if it really was a pin/interface issue that should have caused a sign. Additionally the known ECM issue usually seems to cause the Jeep to completely die and then it takes some effort to get it to start again. Not the case here (unless this is the very early beginnings of said issue).

It is also not the "screw" issue because the screws that people think are too long don't touch the board anywhere near any traces.

The crank position sensor was replaced about 2 months ago because it was failed. This issue didn't exist at that point. I'm not sure I believe it is the crank position sensor again because this is a pretty random issue and there is no indication that the gauges freak out when the stumble occurs. A CPS will cause the gauges to freak and do odd things. Also when a CPS goes it is usually all or nothing - none of this random intermittent BS.

I also know it isn't anything like a loose wire that is wiggled/jostled with a bump because the one and only time it has done it for me it did it while sitting in my driveway idling. Basically it was like someone killed the spark for a second. There was no lead up and nothing after it. Just died for literally a second and then picked right back up again.

The fact that it did it while idling sort of rules out the TPS as the sensor hadn't moved in quite some time.

That leaves the following in my mind:

• Cam position sensor
• MAP
• ECM (Still not sold either way)
• *Remote* possibility of another failed crank position sensor

Data stream on the TPS and MAP look fine. O2s look fine as well.

Anyone have any thoughts to share on the matter?

CrazyMacaw

I went through the same thing with mine a little over a year ago. Mine turned out to actually be a bad ECM and I replaced it and things were great for about 10 months. Then one day out of the blue it started acting up again. I thought it the CPS so I replaced it with a factory sensor and it ran great for a couple of days then it was back to stumbling and stalling getting more frequent each passing day.

When mine stumbled or stalled all gauges, lights, radio and such would stay on, it was only the motor that would lose power and like yours sometimes it came back on its own and other times I had to pull over and crank and crank and it never gave a code.

Well one night she stalled on me and I'd crank and she would start and run for a minute then die again and sometimes crank and crank with no start. While I was looking under the hood I leaned on my battery and noticed a tiny arc, I mean tiny almost invisible. I thought to myself crap that's not good. The battery terminals were clean and tight and the arc actually came from where the wires went into the factory connectors not where the connectors attached to the battery. The wires didn't seem loose but I jammed them up into the connector and the thing fired right up and took me home without even so much as a hiccup.
The next day I went outside and tried to replicate the stall by messing with the battery wires but couldn't do it but I knew that arc I saw was a bad thing so I replaced the terminal connectors and for the last 4 months I haven't had an issue.

Evil Drew M

For what it's worth I just pulled the ECM and all the pins are spotless. No signs of arcing or corrosion. I shot them with QD electric parts cleaner and packed them with dielectric grease but in this case I'd wager that it isn't a connector issue.

jknob1986

02 grand cherokee im having the same problem as we spean just replaced cam/crank sensor coil and the computer... H>E>>L>>>P!!!!!!!!!!!!!!!!!

Evil Drew M

As an update the ZJ I'm dealing with is NOT fixed. Here is the list of what has been done:

• Crank Position Sensor (Prior to this latest issue)
• TPS
• MAP
• Coil
• Cam Position Sensor
• ECM

It runs for 4-5 days after the ECM is reset and then it starts stalling. This is a classic sign of a failed ECM but the ECM is brand new and I have a hard time believing that the new ECM is bad given the exact same pattern of failures both before and after it's replacement.


I'm about out of ideas. Anyone?

Evil Drew M

Oh - also replaced ASD and fuel pump relays.

fishcreeker

On my 97 I went through 3 ECMs before I got a good one. Exact same problems as yours. They were all rebuilds. First one lasted 3 weeks before problems again, 2nd one 1 week. This last is on week 7 and seems fine. I had chrysler flash the last one,seems to run better now than ever.

CrazyMacaw

I dont believe there is such a thing as a "brand new" ECM for a 97 ZJ. They havent made them in quite some time. Everything available today is remanned or rebuilt which seems to mean different things to different suppliers. To me it would mean opening the unit, replacing the components inside ( at the very least the known weak or problematic ones) and reflowing all of the solder points. It seems like a lot of the suppliers just give them a bit of a vibration/bench test, flash the software if needed, repaint the box and sendem on out.

fishcreeker

Chrysler said they dould get a brand new one for $750 or get a rebuilt one from NAPA for $400. I chose the rebuilt to save money. I believe there are new ones out according to the dealer.

N8BIG

Just by chance did you check the ground on the block by the oil dipstick tube? My 98 had broken off and I put a new connector on it and mine has not done it since. also the other grounds from the engine to the body and the battery to the body should also be checked.

Did this problem just jump out nowhere? Or was somebody working on something else and bump something?

Bassmanbob

Try the fuel rail and the Injectors and there is a fix on google called 96ZJ 4.0 multiple Random Misfire SOLVED try that I am going to do same