[Mean Green]

Originally Posted by thebearII

My 2001 PT Cruiser has developed a problem and I can't seem to figure out what is wrong.

My wife drives the car and she complained about it surging when sitting at a stop light. She always drives with the AC on.

I tested the car and it did exatly what she said, I also discovered when you rev it up in park, it acts almost like you're hitting a rev limiter. It revs about half way and then surges like a rev limiter has kicked in. Sorry I didn't look at the tach. The surge at idle in gear (automatic) seems to go away a little when you turn off the AC.

On my test drive the surge would happen while stopped at a light. While driving I floored the gas pedal and expected the surge to happen but it didn't the car felt fine all the way past 65MPH. That surprised me.

I thought the AC compressor might be freezing up but no evidence of any problem when watching the belt with the AC on in park at idle.

I did notice with the hood up and in park if I stomped on the gas pedal I would hear a sound similar to a pop off valve just before the engine began to rev up, almost as if a hose had come loose. I checked for loose hoses, didn't find any.

So I told my wife to drive the car the next day on her errands. She said it was fine except for the surging at the stop light. However, on her way home the temperature guage pegged, hot idiot light came on and when she parked the car she could hear the coolant boiling into the overflow tank.

I looked again to see if the belt had broken, thinking the AC compressor had foze up and the belt broke....it was fine and all looked OK. I could not see the water pump so I don't know if it froze up and is causing the problem. No squeal like the belt is rubbing against a dead pulley so I don't think the water pump is the problem.

No water shows on the oil dip stick.

Sorry for the long story but I wanted too make sure you had as much info as possible.

Any ideas ?????

The Bear II

With surging it is usually the TPS, throttle position sensor. You come to a stop and the rpm's shoot up to like 2k.