celica surging

[Bsktball55]

My wife's 2000 celica is reving when you come to a stop or it is in neutral. It is intermittent so the dealer couldn't get it to repeat, but when you go to stop, the engine will rev up to about 2,500 rpms so it is like someone is stepping on the gas as you are trying to stop. Other times when it is idling it will continuously go between 1,000 and 2,500 rpms like you are sitting there tapping on the gas. Does anyone have any idea of what could cause this to happen? It can be dangerous as you are trying to stop and the engine is revving up causing the car to go forward. It will go 30-35 mph without ever touching the gas. It happened to her 3 or 4 times last week. The rest of the time it is running normal.

[mustang67408]

There are a few things that might cause this.
1: Check to make sure the vehicle is full of coolant, if the coolant is low, the IAC motor may not come off of high idle and when the TPS is showing the throttle closed with high rpm's, the ecu will go into fuel cut causing the 1000rpm-2500rpm engine speed shift as you described.
2: the IAC motor is malfunctioning
3: the TPS is malfunctioning

Have any codes stored?

[Bsktball55]

There has not been any codes that have been stored. The dealer had the car for two days and never got it to act up or throw any codes. It has ran fine the last couple days, but the problem seems to be intermittent.