Blackcherokee290

Okay so this is weird, I have a 2000 Jeep Cherokee Classic 4.0L I6 4WD:


I installed a extended idle switch to the jeeps computer (after I tested it and confirmed the idle went up to 1000 rpm when I grounded the computer pin) by soldering in a switch to go from the computer pin to ground - worked fine.


Used it intermittently (sometimes for up to an hour) on a road trip through Nevada (hotter than hell) - NO issues and always ran the AC


Used it at home here for about 40 minutes (using A/C too) while having a long ham radio chat (transmitting at 50watts can drain the battery fast) and like 45 minutes into it the engine RPM goes up to like 1500 rpm....then goes slightly erratic before settling back at 1000 RPM, chalked it up to maybe pulling too much power or something with the ham radio.


Then I used it for a unplanned 60 minutes (again using A/C) waiting for a friend (again I was transmitting with the ham radio but only at 25watts), at about 65 minutes the RPMs jump to 1500RPM and then drop to 300RPM and the engine runs like crap. I shut off the idle switch and turned on the auxiliary cooling fan (to blow heat out of the engine bay) and turned up the heater and rolled down the windows. The idle switch would not work after this.


A few miles down the road I try it again and it works.


Now it sorta idles low and I had a thought: I reset the computer about 50 miles before I left on my trip, maybe the computer got all confused (since it was in fast-learn mode) when I used the extended idle switch before it completed its (50 I think) warm up cycles it has to go through before it exits fast-learn mode. I looked everywhere and my model CAN be outfitted with the switch and it just is a switch straight to ground....but maybe too much current flowed to ground??? I have no idea WTF happened. Anyone who has any thoughts on this is welcome to put in their 2 cents. I have since cut out the idle switch and am letting the car computer reset again by pulling the power.

SeriousOffroad

Extended idle only works in Park.

Turn it on when your parked then put it in gear...Extended Idle is disabled by the PCM.

SeriousOffroad

PCM automatically adjusts idle when A/C is on, whether you have an Extended Idle Switch or not.

Blackcherokee290

See thats what's weird....it stopped working while in park, i tried neutral too and no go. But after i drove a few miles i dropped it back into neutral at a red light and turned on the extended idle switch and it started workin again. And yeah i thought it was the ac causing the high idle, but it does a high idle at warmup every morning with or without the ac. Just really trippy trying to figure it out.

thatXJguy

Mine works in park AND neutral, and from what I understand, that's how it's supposed to work, just not in drive or reverse. It's a Mopar switch.

The switch will only idle high when you're at a stand still also. If you're rolling, it will idle normal until the vehicle comes to a complete stop.

I would check that you don't have a bad connection in your switch or elsewhere. Here's a guide I wrote:

https://www.cherokeeforum.com/f51/ho...switch-204925/

SeriousOffroad

The only difference between Park and Neutral is the position of the pawl in the transmission, so of course the extended idle works in neutral.

Blackcherokee290

Okay thanks for the suggestion about the bad connections and the write up link, i actually used your write up to do the job.

And yea i know the pawl is all that makes the difference (at a red light i didnt want to freak out the driver behind me by putting it in park lol), i just wanted to say exactly what happened - i never was rolling when the idle got weird, always stopped. I have a feeling its going to be impossible to track this **** down. I'll double check the connections though.