Engine races when car is partially warmed up and restarted.

Dear Tom & Ray:

I have a four-cylinder 1986 Ford Taurus. It has a problem which has baffled
the mechanics at my Ford dealer. When the car is partially warmed up and is
restarted after having been off for a while, the engine races. And it only
does this in the spring and fall when temperatures are cool. In the summer
and dead of winter, it's OK. The dealer has tuned it up, replaced the
computer and the idle air control, all to no avail. It acts exactly the
same. Should I junk it and ride my bike?-- Bill

RAY: The bike might be a little faster going up hills, if I remember the
four-cylinder Taurus correctly, Bill. But I don't think things are that
desperate yet.

TOM: The dealer made two good guesses, and given that neither one did the
trick, my next guess would be an out-of-specification coolant temperature
sensor. A coolant temp sensor that's on the fritz could easily send a wacko
signal to the computer under certain conditions, and that could cause the
computer to boost the idle unnecessarily.
RAY: A new coolant temp sensor costs about 20 bucks, Bill. So see if your
dealer is willing to make a trade. Tell him you'll give him that new
computer you didn't need if he'll give you a new coolant temp sensor and
about 380 bucks. Good luck.
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