IndyKeith

1999 Cherokee Sport - 257,000 miles

It's been running great, but has suddenly started dying after a few miles of driving. It will restart, once, for about 30 seconds before it dies again. Then it won't start for an hour or so, and the whole process repeats itself.

I hooked up a code reader and had 2 error codes:

P0138 O2 sensor circuit / high voltage bank 1 / sensor 2
P0141 O2 sensor heater / circuit bank 1 / sensor 2

I changed both O2 sensors; I think the originals were still in there.

The cherokee runs much smoother, but the same thing happened. No error codes.

When it stalls, I assume it's losing spark. There's no sputtering or surging. Nothing but a silent stall. But I don't see why that would only happen after the car reaches 180 degrees or so.

I'm good at turning a wrench, but lack troubleshooting skills.

What is a good next step?

Thank you

tjwalker

I don't think that the oxygen code issue is related to your "no start hot" issue.

It really would be helpful to know what component you are missing when it won't start. Only takes 5 minutes to confirm. Take out a plug, keep it attached to the plug wire, place the plug electrode near a good engine ground. Have a buddy turn the engine over while you watch. You are looking for a strong, BLUE, snapping spark. Yellow, orange, white indicates a weak spark which can be caused by a failing ignition coil.

If you have NO spark, the #1 culprit is the crankshaft position sensor. This sensor absolutely can suffer from thermal failure. Search for testing procedures. If you replace it, do yourself a favor and use a genuine Mopar sensor. Aftermarket crank sensors and "hit and miss" with quite a bit of miss in my opinion.

The ignition coil can also suffer from thermal failure and can also be tested, but the crank sensor fail happens more frequently.

Spark: 12 volts from ignition switch to the ASD relay; when the key is first turned on the PCM provides a ground to the ASD relay to energize it, then the ASD relay passes 12 volts to the coil primary side. If no crank sensor signal is generated after a couple of seconds the PCM cuts the ground to the ASD relay (and fuel pump relay too) and that cuts power to the coil (and fuel pump). Key to START and once again the PCM energizes the ASD relay. Now, a critical element is the crank sensor--no signal from the crank sensor and the PCM won't trigger the coil to provide spark.

Good luck and be sure to keep us updated!

BlueRidgeMark

Here's a troubshooting tip for this particular probllem: ICE.

Or, COLD, at least.

After following TJ's instructions above, and while it's still hot enough to not start, ice the suspected component. In this case, the CPS first. It's tough to get to, but you should be able to get some ice or at least very cold water on it, OR, if you aren't happy about spraying cold water on an electrical component, use . If cooling the component gets you running again, you have identified your culprit.

BTW, a short spritz won't do it. Spray that thing down good!

Sluntpunch

Sounds like you have a fuel pump issue. A couple years ago I had similar symptoms. Jeep would stall out, limp it home. Then the next morning it would start and run fine. Took it to a shop, they told me the fuel pumps was going out. So I replaced it (easy job to do) no more problems.

BlueRidgeMark

We prefer to advise people to test their way to a solution rather than blindly swap parts because it worked for somebody else.

IndyKeith

There's no spark after it stalls. The cold spray does allow it to restart. Cooling it at least allows me to drive to the store and back reliably, which is only a couple of miles away.

I've ordered a CPS, it will be here tomorrow.

Thanks for the help.

Keith

IndyKeith

I got the old part out. I attached a photo of my ratchet/extension combo. Maybe it will be helpful to someone else.

I went in head first from the drivers side. Feet first would be easier for a righty, but my gut won't fit under my stock height truck, and I was too lazy to jack it up.

The bottom bolt came out in less than a minute. The top one took a little more effort to get the socket on the bolt, but still took less than 5 mins. I worked from the right side of the driveshaft, but sighted from the left. I got both bolts 90% of the way out with the socket and then pulled them out by hand from above.

Dropping the driveshaft would make it a lot easier.

Hopefully, I can just reverse the process of installing the new part when it arrives.

Keith

BlueRidgeMark

Cool.

Kat smith

Did that fix the problem? I am having the exact same issue

Saudade

This thread is 5 years old. The OP hasn't been here since 2018. I would not expect a reply. Instead you should start a new thread highlighting any issue you are having rather than bump old posts.

Welcome to the forum.

lawsoncl

But, yes crankshaft position sensor would be my first guess in your case as well. Often does not set a code. You might be able to confirm it's become heat sensitive by blowing some canned air (upside down to get the freeze spray) on it to chill it when it's not working and see if that gets it going again.