Motor redlined with no throttle input....wtf?

Alright, mom has a Jeep XJ also.

She comes home all nervous and says she was sitting at a red light, foot on brake pedal, and all of a sudden, she said the Jeep revved as high as it could and held there until she turned the key off.

She always seems to have weird things happen when she is driving a car, and without me being there, I really do not know what to think.

I think she is crazy, but she says it did that.

Thoughts:

Even if the IAC somehow jumped all the way open, it would still not rev very high because of the physical limitations of the air flow through the IAC.

If a large vacuum line came loose, sure, it would idle high, like 1500-2000rpms (like brake booster line) but still no where near redline.

The Jeep has cruise control which has never worked. Even if the diaphragm could some how pull the throttle plate open, cruise control doesn't engage at low speeds. And I do no believe it would open the plate to WOT.

I could understand if she was driving and the throttle got stock, but she was sitting still. I checked the linkage and everything looks fine.


Any ideas??? She is afraid to drive the thing now. I have since driven it and there are no problems.

Help!!!

Her purse fell onto the gas pedal?

Someone had the same problem here recently. The problem was real. As I recall it had something to do with the intake manifold being the source of the extra air in his case.

It does not take WOT to redline the engine in park or neutral (no load). You did not say how high the RPMs got. Mine got as high as 3000 rpm in park, 1500 in drive on several occasions. Several problems caused it at different times, once was a bad MAT, another was a loose, dirty ground wire (causing a variable ground resistance that affected the TPS voltage to the ECU. Another was a stuck IAC.

Found it:
http://www.naxja.org/forum/showthread.php?t=901241

Mom's got big feet and was hitting the gas pedal a bit?