[Oldfrog]

97 GC laredo 4.0. 189K miles. When it's not stalling it runs great. All this started after my driver's side window controls stopped working and I cleaned the air conditioner drain. ( no broken wires in the driver's door, BTW) One day it wouldnt start, so I replaced the battery. It was downhill from there.

Here's the history. I hope someone can tell me the fix for this. It's driving me nutso ! Six months of this is too much.

Stalling....as if ignition was turned off. Sometimes it just bucks once, and the computer goes haywire, messing with the timing, etc...and it stumbles. Sometimes I can floor it and it will run again...but most times I have to kill it, or it just dies.


New battery and cleaned clamps to a shine.
New TPS ( although suspect)...Wells brand.
New IAC , cleaned throttle body..no change...so I reinstalled the original MOPAR.
New CPS ( MOPAR)
New Cam sensor ( autozone), distrib. cap, rotor, plugs.
New Coolant temp sensor.
New primary coil.
Cat convertor is one or two years old. ( meineke)
Backed out two torx screws on PCM ( a known issue...they are too long)
New Fuel pump, filters and cleaned tank.

New battery was load tested.

Advance auto ( whom I dont trust) said the alternator wasnt putting out enough amperage at 1400 RPM. I never have had a charging problem, though.

Just before I installed the new fuel pump, it would start/die/start/die.

It seems stall mainly after it warms up to operating temp, or on warm days...( above 55 degrees).

Cleaned and tightened two ground wires on sides of engine block as well as the fenderwell.

Oh yeah, I'm getting some oil in my air cleaner. I suppose that's a plugged CCV hose. Would that do it ? Sometimes when it acts up, I DO smell crankcase fumes.

Any ideas, other than ECM ?

[CrazyDrivinJoe]

the oil in ur air filter is comming from the the hose that goes from the top end to the air filter I have a small air filter in that spot now and after market intake

[SJZ]

Any codes?

[Oldfrog]

It would mainly throw a 43 and when checked with a code reader, it was a P0351. That's why I replaced the coil.
Bad connecting pin at ECM?

I have started it an wiggled every wire in the engine compartment. No change. Something is heating up.

I have had it do it when I drove over some bumpy terrain at times, right after it first started stalling on me. Now it just stalls at random.

[Oldfrog]

Long ago, after a stalling episode, the codes were P0320 ( no crank reference) and the 351. No primary coil signal.

It has a new MOPAR CPS and I have jiggled wires til I'm blue in the face. Of course, I cant make it stall.

I DO have some oil leaking from either the rear main seal or from the rear of the valve cover. When I replaced the CPS a few months ago, there was some oil on it. Is THIS my problem ? Would a bit of oil on the CPS stop the signal after it heats up?

[SJZ]

Have you looked at the ASD relay? Just a thought.
How often does this happen, and does it restart right away?

[Oldfrog]

I have swapped the relay with the other two. No change.

It happens all the time. I can count on losing igntion after it heats up to operating temp, so I'm afraid to go very far in it now.

Most of the time it starts back up....but lately, it's been taking 4 or more tries to make it start without the timing being off. I think the ECM resets to default after 4 bad start attempts.

But yes, it would seem that something ( a short, etc.) is causing the ASD relay to trip. I'm wondering if my oil leak is causing a bad CPS signal at times. A few months ago, I thought I noticed that it died more often while I was sitting at a redlight , facing uphill.

I can be driving down the road now and all is well, when BUMP ! ~ It loses all ignition. Sometimes it recovers on it's own but it felt like I hit brick wall for a second.

It's got to be something that is causing the ignition to shut down intermittently. The "heat soak" thing is almost certain. If I stop at a store for a coke, for example...and come back out to restart the Jeep, it starts doing the stalling, backfiring, stumbling thing badly.

You guys are my last hope. I dont want to take it to the stealership. Because we all know they will just want to throw more parts at it. I've done that myself already

[leftfield6]

I went through a lot of the same symptoms as you, although mine NEVER threw a code, and it wasn't as closely correlated to engine temp as yours seems to be. Not an exact match, so YMMV on what worked for me.

I replaced parts, in a search and destroy mode, the crank angle sensor, the cam positioning sensor, ignition wires, coil, plugs, etc.

I also changed to shorter screws in the ECU, like you tried.

All to no effect. Eventually swapped out the ECU with a remanufactured one from a company in FL. I think it was around $300 with core return. That was 4 months ago, has ran perfectly ever since.

Like I said, not an exact match to your symptoms, but take it for what it's worth.

[Oldfrog]

That would be fine, if I knew it was the problem.
I have spent nearly $1000 on it already. On a Jeep that's 11 years old this April. How smart is that ? As you can tell, I love this Jeep, even if it's my third one.

Unless I find this problem soon, it'll be my last, but I really dont want to part with it yet.

Does anyone know of a case where an oil leak was affecting the CPS signal? Surely the magnet is not that weak.

[95ZJ-tilshedies]

Originally Posted by Oldfrog

Does anyone know of a case where an oil leak was affecting the CPS signal? Surely the magnet is not that weak.

I was having almost the exact same symptoms as you --- including the fairly severe rear main seal leak -- (I am fixing my rear main this weekend). I replaced my CPS a month ago, and have not had a problem since. Your theory is really interesting -- I did notice the CPS that I removed wasn't covered in oil --- is there a lot of oil getting to the top of your bellhousing?

[Oldfrog]

I'm sure there's oil on the bellhousing.

But you just gave me a thought. I replaced the CPS about 2 months ago...and noticed that while I was tightening the bolt, after several turns, it seemed very hard, as if it were crossthreaded. Now, understand that I've been working on cars and race bikes for over 30 years, and I know not to keep cranking on a cross threaded bolt. As I recall, I backed it out a bit , then cranked it down a bit more....and checked it as best I could. It seemed tight at the time...but who knows when you have 28 inches or so of socket extensions flopping around on your ratchet? Man ! I do NOT want to go under there and deal with that CPS again !

I had a heckuva time getting my hand up in there, due to the front drive shaft. But if that CPS is moving ever so slightly after the bellhousing heats up, that could do it, couldnt it ?

[OnlyJeep4me]

Have you checked the connector pins on the ECU? If there is any rust that can cause problems like your describing. My 96 XJ went through a spell like this at 243,000 miles and I replaced the IAC and never had another problem.

[95ZJ-tilshedies]

Originally Posted by Oldfrog

But if that CPS is moving ever so slightly after the bellhousing heats up, that could do it, couldnt it ?

It seems to me like it could. I know what you mean about getting to that PITA

I struggled for months before I decided what to replace first; I really didn't want to go through what you have gone through. Below is pasted from the FCM for a '95: This is what convinced me to start with the CPS; it explained (to me) why it was happening so randomly; it sounds to me like you have a reasonable explanation as to why your sensor might be failing...

SENSOR OPERATION—4.0L ENGINE
The flywheel/drive plate has groups of four notches
at its outer edge. On 4.0L engines there are three
sets of notches (Fig. 6).
The notches cause a pulse to be generated when
they pass under the sensor. The pulses are the input
to the PCM. For each engine revolution there are
there are 3 groups of four pulses generated on 4.0L
6-cylinder engines.
The trailing edge of the fourth notch, which causes
the pulse, is four degrees before top dead center
(TDC) of the corresponding piston.
The engine will not operate if the PCM does not receive
a crankshaft position sensor input.

[Oldfrog]

Havent checked connector pins at ECU, other than wiggling the heck out of the plugs and wiring while it was running. It didnt make it die.

If it WAS the CPS ( remember, it's a new Mopar CPS)....one would think it wouldnt run as well as it does, eh ?

What I mean by that is, if it isnt stalling it runs great, sometimes for long stretches of time, non stop. Today, there was about an hour of stop and go city driving when it didnt try to die even once. Then all of a sudden, it bucked a few times....and kept going.

Later,at a redlight, it spit and sputtered, backfired and died...with crankcase smoke coming out from under the hood. ( I suppose it was thru the air cleaner).

It started back up after a couple of tries and it ran fine again. Go figure. It sure sounds like the CPS, though, the more I think about it.

But before I tackle that again, I need all the info I can try beforehand.

[95ZJ-tilshedies]

Originally Posted by Oldfrog

If it WAS the CPS ( remember, it's a new Mopar CPS)....one would think it wouldnt run as well as it does, eh ?

What I mean by that is, if it isnt stalling it runs great, sometimes for long stretches of time, non stop. Today, there was about an hour of stop and go city driving when it didnt try to die even once. Then all of a sudden, it bucked a few times....and kept going.

I disagree: The FSM says "The engine will not operate if the PCM does not receive a crankshaft position sensor input." To me that meant that the engine would be running like a top, and the second that the signal was lost from the CPS, the engine would shut off (this is what mine was doing) --- but as I would keep rolling at highway speed, the signal from the CPS (for whatever reason) would be restored, and the engine would kick back in and continue running as if nothing ever happened.

Originally Posted by Oldfrog

But before I tackle that again, I need all the info I can try beforehand.

I hear you!!! good luck!