My 1999 XJ Automatic is getting random increases of rpm while driving.
I dont know how high the rpm gets but when I let go off the brakes while driving it almost runs by itself without the need of giving it gas.

Sometimes it happens ,sometimes not. I checked for possible vacuum leaks but couldnt find anything.


What could be the cause of random high rpm's?

thanks in advance guys

 

Idle air control motor probably.

 

where is that located?

 

On the throttle body. There are two things with wires going to them. The one on the right should be the throttle position sensor. The one on the left should be the idle air control motor

 

It happens when your foot is off the gas right?

 

TPS is on the rear of the throttle body (1996). IAC is on the side closer to the valve cover?

 

My 99 does the same thing so I hope you figure it out. I will replace the IAC sometime this week.

 

It stopped doing it. But now sometimes when I shift into reverse in takes a while to shift gear.

My Cherokee has a new TPS sensor and I cleaned the IAC a few months ago.

Must be something else

 

Check for codes !