Stock 1999 Cherokee Sport 4WD, 4 door, Auto

When I am driving around, there is a sudden loss of RPMs then it goes back to around 750rpm. Also, the RPMs drop below 750 then back up if I take my foot off the gas quickly then coast to a stop. Then, if I put it in park or neutral the RPM's go up to 1000 and hover there.

This seems to happen only when my AC is on, not with the heat/defrost (or nothing). It seems to go back to normal after I park it for a bit, but comes back when I turn on the ac. There is the regular twitch in the RPMs when heat/ac is off but think that is commonplace with Cherokees.

No check engine lights. Recently replaced downstream O2 sensor to try and fix this problem, but still occurring.

Any Ideas?

Thanks,

Paul

 

i had a simular problem a while back where crusing at 55 60 mph the rpm's would drop down from 1800 to sometimes below 450 rpm's kinda makes like a sudden jurk like the jeeps turning off and back on real fast.after changing many parts found out it was the throttle position sensor. hope this helps you

 

Could be the IAC valve is starting to fail.

 

yeah, try iac or tps first. Clean iac, don't replace at first. AC also commands the iac to increase idle, so since it happens more with ac on I would definitly start there.

 

Cleaned IAC, we will check tomorrow on the drive to work...thanks