Ok this one is driving me nuts .... Sometimes when I'm coming to a stop or just slowing down with my foot on the brake my xj will just speed up for a second.... pretty hard too. I can see the rpm's go up a little when it happens. I was at a stoplight last night, almost completly stopped, and then my car just revs up. I had to put all my weight on the brake to stop the car. It only lasted for second and maybe happens every three days or something. What can this possibly be?

Check and clean your IAC.

what does IAC stand for? thanks

Idle Air Control sonser/motor,its on the front of the throttle body.

My wifes pt cruiser had that issue. The only codes i could get for it were for the cooling system. I replaced the thermostat, and the ect sensor. Not sure how its connected. but it hasn't done that since.

I had someone tell me that if a sensor is bad, it will send a bas msg to the computer. And then the computer makes the car act like what its being told is wrong.

I'm not a guru like some of the guys on here, but id go to the parts store and pull the codes. Start with the cheapest part, and go from there...

thats the thing when mine was bad It would idle up really high.I pulled it out cleaned it,didn't help.Ended up just replaceing it.Worked out fine.

Agreed, this is the first place to look for any idle issues. Its a small motor that opens when the throttle is closed to allow a steady idle. It may be sticking and in turn causes the a high idle issue.

ok thanks guys. I'll go check it out.