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97 Jeep Laredo 6-cyl stalls intermittently when warm

1997 jeep 6cyl, runs perfectly but last week began stalling while idling in city traffic, then is hard to start and acts like its running out of gas. After sitting a few minutes, I get it running and limp home while racing the engine.

I’m in San Francisco and it first happened after sitting in the warm sun following 2 months of constant rain & cold. Happened again 2 days later under similar conditions. It still starts easy and runs perfect when the engine is cold mornings & evenings or on the freeway anytime, but the problem is intermittent and sometimes stalls after getting off the freeway, while idling with my foot off the gas even on chilly nights. Other times is fine under the same conditions.

I thought it was moisture due to all the recent rain, possibly vaporizing in the sun, so I’ve been keeping my gas tank full and took a 3-hour road trip hoping to clear it out.

I took it to a mechanic who could not reproduce the problem, but found a fault code p0351 - ignition control circuit for cylinder 1 malfunction. He said to replace the distributor, but only 70% hopeful that would fix it.

Another mechanic guessed a throttle position sensor. Others agree they can’t tell unless I can reproduce the problem in front of them, but so far I cannot. The engine idle speed seems slightly lower now (about 500 rpm) than last month but I can’t adjust it.

Any suggestions? How can I narrow this down to fuel or ignition problem?

1997 jeep grand cherokee laredo 4wd, inline-6cyl, auto trans, 170k miles, no engine warning lights.

The most common problems with a p0351 on a 4 litre jeep has nothing to do with distributor or tps. Unless the tech can duplicate the problem, it will just be parts slinging. The most common fixes from most popular to least are: computer, coil, crank sensor, coil connector, wiring. The big problem though is duplicating and diagnosing. The ignition problem is pretty obvious. It’s not fuel. Actual definition of P0351 is ignition coil 1 primary circuit malfunction. One thing to check that I have seen quite a bit of is the rear oxygen sensor wiring laying on the exhaust.

Looks like you were right… seems to have been the computer (PCM). I took the car to a jeep specialist on Sutter st. in San Francisco and he thought it was the coil. Luckily it stalled after replacing it (no charge), so he concluded a bad PCM. Seems fixed now, I hope it lasts.

Assuming this is the true fix: I’m lucky I didn’t replace a bunch of other stuff, but I’m a little disappointed in Jeep. The PCM is about the most expensive engine part, and there is no way to test it, or for the home mechanic to replace it, and the idea of solid state is no moving parts so why should this fail? Seems crazy to add a bunch of controls to an engine and then use a computer to make it run… i suppose all cars work this way now, but stalling is a deal-breaker.

In my research online I found so many others with this same problem. There was talk of some jeeps “eating” PCMs, and even a web-site trying to profit from this PCM situation. I’m left feeling that Jeep messed up on this.

A few days after the new PCM my Jeep began stalling when cold (the opposite problem). Never did that before and I returned to the shop. Battery was suspect, replaced it, no luck so the shop kept the car for a week and observed the problem but could not locate the cause. They said it was maybe “bad gas”. That sounded fishy or an amazing coincidence but I started using Chevron not the discount brand… and three fill-ups later the engine is running better, not stalling, but not normal either. Occasionally the engine stumbles, misses or nearly dies but then recovers and runs perfectly again. usually while driving. If it happened while stopped I believe it would stall. I’ve never had this much trouble with an engine and surprised at the number of people with similar problems.

“Bad gas” is code for “we don’t have any idea.”

Is that check engine light back on? Have it scanned for codes either way.

No check lights but it has continued to run poorly off and on, and now 2 months later I’m just dumping it. Recently I can’t start it, for hours. I was stranded once on the freeway so far. I’ve stopped trying to reason it through. Basically the engine won’t run right and fixing one symptom only makes a new one appear. It’s stumped the all-brand shops and the Jeep experts alike. But I’m mostly impressed with the number of people with my same experience and the myraid would-be solutions. I pick up my new car tomorrow–no more Jeeps.