Erratic idling, hard starts, AW4 problems

Been searching and have found some info, but not sure where else to go about this.

98 xj AW4.

Jeep will start up normal when cold, idle and drive w/normal shifting.

Once it warms up, it will sometimes idle very rough, and sometimes die. When it dies, it will crank but not start until it's been sitting for about 20 mins.

I have changed the coil, and CPS, and nothing.

Once warm, tranny will sometimes slip, and only go back into 1-2, or Rev. Shifting from 1-2, 3, OD works, but if I gas it in 1-2, it accelerates very slowly.

Changed fluid (dex III) and filter - nothing.

Pulled code P0758 - solenoid b. Was about to order a pack, but read also that it could be a bad TPS?

Would that be the next step you guys would take? I also found it could be a bad TCM. This thing is driving me crazy.

When you drove with manual shifting, was that with the TCU disconnected?

No, I have not disconnected it yet. What do I do to test that? And where is it on a 98? Pass side under glove box?

Your TCU is located under the driver's side of the dash, between your right knee and the airbox.

That code should have been P0756 for solenoid B--recheck it.

The TPS wouldn't give you that code, but might be related to the running issue (maybe). When was the last time the upstream o2 sensor was changed??

Checked twice and both times it said P0758. Checkers only said shift solenoid, advance said solenoid b.

When I searched the code online, results came up for solenoid b as well. :dunno:

W/the jeep running, I disco'd the tps and it went into a nice idle. Could that be the problem?

I picked a set of 3 solenoids for free today. From a 92 xj though. Going to drop the pan today and hope they are the same ones.

On 02 sensors, not sure.. I just bought this xj a few weeks ago. I was told about the tranny problem, but not the idling problem.

djlarroc said:

W/the jeep running, I disco'd the tps and it went into a nice idle. Could that be the problem?

Click to expand...

yes, the trans needs good TPS data to determine when it should shift, and the ECU obviously needs it to sense the throttle position.

If you have access to an analog meter, or a good fast reacting digital meter it's not hard to test.

You should see a smooth change in the voltage, any errattic jumps or dead spots indicate it needs replacing.