i have a 1990 accord with a 2.2 sohc with 250k. for the past couple weeks when i starting in the morning or when leaving work (cold engine) the idle jumps between 800 to 2000 rpm. when the engine warms up the idle is fine. some people are telling me that is a coolant temp sensor. are they right. i don't want to start throwing parts in to it.

 

i had a similar problem and it was the O2 sensor...just a thought

 

Be sure the coolant is full and block burped thru the12mm bleed screw at the T-stat housing; Then adjust the FITV ....turn it in a couple turns or until the cold idle surge smooths out.
OR if you want to waste some money throw an O2 sensor at it.

 

Please Search next time. This is not a new topic.

 

I have been working on the same problem.After replacing the brake booster it does the
surging about half of the time.Try plugging off the booster vacuum hose before starting
cold and see if it helps.

 

dammit i just posted this somewhere... look through my posts and find the one about the cold start wax valve.

 

The fast idle valve probably needs to be replaced, also the intake air temp sensor. That is most likely the cause. The throttle position sensor can bring these symptoms as well.

 

After replacing the brake booster it was still surging about half of the time.I ordered a
new fast idle thermal valve (f.i.t.v) from the dealer.Problem solved.