High idle

[Jeepgcce]

Hello jeepz users,
I've had a problem with high idle for a few days now. I have replaced IAC valve, MAP sensor, and TPS. There for awhile it would idle anywhere between 1100 and 2000 if gas pedal is pressed and released it jumps to 3000 and stays there. I've checked for vacuum leaks and fuses even tested alternator and heard about low power steering could cause high idle. But it was full. So I drove it as is and it would eventually go into limp mode. Of course tried cutting it off and restarting but only for it to go a little farther and go limo mode again. I bought another IAC valve and it seems to work a little better but still getting high idle and limp mode is gone. Any help would be greatly appreciated. Really need fixed ASAP as it's the only form of transportation I have at the moment. Thanks.

2004 Jeep Grand Cherokee Columbia edition
4.0
4x4

 

[JPNinPA]

You have a vacuum leak.
Look for a disconnected or cracked vac line. With engine running Take WD40 or TB cleaner and spray around each vacuum line, injector spark plug intake to cylinder and base of TB. Listen for the rom to change. There you will find your leak.


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[JPNinPA]

Also make sure the IAC gasket is intact when installing and the TPS just gets placed on do not wind it or twist once on the valve stem.

Also hope you used OEM sensors. Aftermarket parts fail out of the box.

Reset the PCM by disconnecting the battery pos terminal touch it to negative for 15-20 sec. Reattach. Turn key to on position do not start. Turn lights on. Turn lights off then key off. Then try starting. If idling normal let it run for 15 min without driving.


Regards,
JPNinPA

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[JPNinPA]

Any luck?


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[OhNoAO01TJ]

Yes you do have a vacuum leak before you go through the tedious task of checking every vacuum line check all of your bolts on your exhaust manifold, engine block, as well as your exhaust pipe. I've had two different occasions where a manifold bolt was completely missing on my TJ where it would red line at start up.