i have an 89 xj 4.0l 6. now this truck just recieved a new tranny,throtle position sensor. now when the truck is siting there idleing and the motor souunds like it will cut out or die down in revs just for a split second. it will do this warm, cold, in gear and at speed. now it think it could be the idle air valve in the throtle body, but is there a way to check it or does someone know what the problem is or what else to check. any addvise is helpful.

I have a '91 Cherokee. It was doing to same thing up until a few months ago when I bought a bottle of fuel injector cleaner and an Oxygen Sensor. That seemed to cure it. Now it starts and runs fine. Give that a shot, the sensor isn't that expensive and it isn't hard to install. Good luck.

pull the idle air stepper motor, and clean it (And the throttle body where it attaches) with wd-40 and an old toothbrush. It really smoothed out the idle on mine, there was a lot of black greasy buildup on the motor and the throttle body.

btw- be gentle you can break the stepper motor if you aren't careful

thanks guys ill give that a try.