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Chris, Shop Foreman
Category: Jeep
Satisfied Customers: 3137
Experience:  Jeep Certified Master Tech
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96 Cherokee 4.0 auto engine installed, will

Customer Question

96 Cherokee 4.0 auto engine installed, will start but dies as soon as I let go of the key. I swapped in a known working pcm from a 99 Cherokee and starts and runs as normal. Here's where it gets weird, the original and a new 96 pcm will run the 99 Cherokee. thoughts?
JA: Does the vehicle have a carburetor?
Customer: no
JA: Are you fixing your Cherokee yourself? What have you tried so far?
Customer: new ckp, new distributor, checked all circuits to related to issue and everything has tested good. fuel pressure ok. like I said it will run on a 99 pcm but I will get codes and gen light due to clusters being different.
JA: Anything else you want the mechanic to know before I connect you?
Customer: nope.
Submitted: 8 days ago.
Category: Jeep
Expert:  Amedee replied 8 days ago.

Hello and welcome!

My name isCustomerand I can assist you with your question.

Expert:  Amedee replied 8 days ago.

This is most likley due to a bad idle air control module located on the side of the throttle body or the PCM just simply needs to learn the idle. How long have you deen driving the vehicle after the engine was installed?

Customer: replied 8 days ago.
How would that make since if it will run on a 99 pcm but not its original 96 pcm? I also have a new 96 pcm, both of which run a different vehicle.
Expert:  Amedee replied 8 days ago.

But it does run no problem above idle correct?

Customer: replied 8 days ago.
With the incorrect pcm yes.
Expert:  Amedee replied 8 days ago.

Probably because the incorrect PCM has a learned idle

Customer: replied 8 days ago.
I've performed memory resets the IACV and cleaned the throttle body during new engine install. No luck, If either of the Correct 96 PCM's for the vehicle didn't have a learned idle then why would they both run a 99?
Expert:  Amedee replied 8 days ago.

Can you upload a video?

Customer: replied 8 days ago.
Of what specifically?
Expert:  Amedee replied 8 days ago.

Everything.. especially of the stalling condition.