I recently bought a 1999 T5 V70 wagon....5 speed stick with 100,000 miles. All is fine EXCEPT, the car hunts at idle between 500 and 1000 rpm. There is a regular pattern of speed-up and slow down.

This is the first fly by wire year, with frequently failed throotle bodies, but this throotle body was already replaced by th last owner in 2003. It has no engine codes, no check engine light. The car starts fine. The throotle body is clean. My independent mechanic thought it was the throotle body...the dealer will not replace it since there is no code. (The dealer is stumped.) The car starts fine and idles at 1000 rpm, then when warm...it hunts. The car runs very smoothly when driving, no drivability issues, good gas mileage.

I've been told is could be a bad coolant temp sensor...but there is no error code.

Any ideas/similar experiences and solutions?