My 2000 OBW with 5MT has recently started fast idling at 3000 RPM. It does back off a bit when going to slow idle, but only down to 2000 RPM. This only happens when the engine is cold. Starting the engine when its warm results in regular idle rates 1.5K RPM fast and 1K RPM slow.
I had a similar situation a year or two ago, and back then I think the problem was with the throttle position sensor. However, back then it would do this all of the time when starting up (it would go down after a few minutes of driving), warm or cold engine. This one only does it when the engine is cold. Previously it would only idle at 1.5K fast and less than 1K slow when starting cold.
Any ideas what could cause this? Oxygen sensor? Something else?
Yousuf Khan