(SOLVED) Weird symptoms with automatic PCM in manual TJ (2.5, AX-5)

Gollywomper · Apr 13, 2022

mrblaine said:
See if you can correlate that to not doing any steering while moving. There is a pressure switch on the steering pressure line that is supposed to let the PCM know when to bump up the idle when the steering is being used. Or maybe sit still and turn the steering wheel to see if it does the idle bump then.

So I checked my PS pressure switch. When it closes it gives the engine a monetary surge at idle. One quick surge then returns to normal idle. If I keep shorting the plug rapidly then the idle will continue to raise.
My high idle while moving continues with zero steering input and with the switch disconnected as well. It is very controlled and consistent. I’m wondering if it is a pcm thing on the 97/98’. My brother in laws 99 does not do it.

SkylinesSuck · Apr 13, 2022

Very interesting. Mine exhibits this behavior, but I thought it was a tuning issue I haven't been able to figure out yet. Maybe I just didn't notice it before? Mine will even do it if I stop on a hill pointed nose down and start rolling in neutral. It goes from choppy chop idle to 1100rpm and stays there until I come to a complete stop with zero throttle input the entire tire.

I heard the JTEC PCM in the Viper had a "max rpm at 'X' speed" parameter you could set to stop this behavior but that option isn't there in HP Tuners for mine. Can somebody with an unmolested TJ check to see if theirs does it?

Gollywomper · Apr 13, 2022

SkylinesSuck said:
Very interesting. Mine exhibits this behavior, but I thought it was a tuning issue I haven't been able to figure out yet. Maybe I just didn't notice it before? Mine will even do it if I stop on a hill pointed nose down and start rolling in neutral. It goes from choppy chop idle to 1100rpm and stays there until I come to a complete stop with zero throttle input the entire tire.

I heard the JTEC PCM in the Viper had a "max rpm at 'X' speed" parameter you could set to stop this behavior but that option isn't there in HP Tuners for mine. Can somebody with an unmolested TJ check to see if theirs does it?

My engine, computer and wiring are all stock.

thedustyboot · Apr 25, 2022

An update to this thread I started. Found a loose ground wire below and aft of the distributor on the passenger side of the engine block. I actually wiggled it while the engine was running and it killed the engine.

PCM is still the same, I’m still acquiring funds to buy the proper PCM.

Will post more updates as I tackle things one by one. And providing work lets me have a couple days off once in a while

thedustyboot · May 13, 2023

It's been a hot minute since there's been any updates to this thread but I only just recently found a manual PCM for my TJ.

As described above with regards to the strange symptoms I've been experiencing, the installation of this new-to-me PCM has solved my symptoms/gremlins.

No more CE light, no more strange high idle when vehicle is moving, and much better throttle control at low rpm's.

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(SOLVED) Weird symptoms with automatic PCM in manual TJ (2.5, AX-5)

Gollywomper

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SkylinesSuck

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Gollywomper

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thedustyboot

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thedustyboot

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