High idle (not linkage)

[Christian Williams <delorean@xxxx>]

Hi guys,

I was holding off on posting this problem until I had my o2 sensor
replaced, which I did this morning.

The problem is that when I start the car up, it idles fine. After driving
25 minutes on the highway to work though, it idles around 1500 RPM. I've
left the car running, opened up the engine compartment, and pushed on the
throttle linkage, but I find that it always returns all the way. The next
time I start the car up (provided that it's cooled off), it idles fine
again.

What else should I check?

Thanks,
Christian