Strange, new idle quirk...

[Rick Lee]

This weekend, while on the way to Philly from Hershey, my car had some strange idling issues. We were in bumper-bumper traffic and I did not get out of first gear for quite a while. My accelerator seemed to me sticking. Once I released the clutch, the car would go by itself and, even up a steep hill, it took some braking to get it to stop. Sometimes I would push in the clutch, take it out of gear and the idle would shoot to about 2500. It went back down after I punched acc. pedal. The pedal always returned when I took my foot off, but the idle would not. What causes this? Thanks.