High idle speed on 1988 Accord

I got a call from my inlaws because thier 88 Accord LX was idling high. I
had changed the timing belt and alternator on this car about 5k miles ago.
No problems, except for a easily fixed squealing belt, after the work was
done. They recently took the car in to get inspected and the mechanic told
them the car was not going to pass inspection unless they cleaned the
carburetor. Apparently the mechanic used a whole can on the carb and then
the car passed inspection. Shortly thereafter the idle speed jumped. When the
car is cold if you step on the gas the idle speed drops to about 1k. After the
car warms up, it idles at around 2k. I'm going to give the car the once over
this weekend. Anyone have any tips on where I might start looking for the
problem?

 

Maybe the carb cleaner he used fouled up a sensor in the carb?

 

What sensor?

 

Is it an auto trans? If so, a common problem with that model (I'm still
driving our '88 Accord LX back and forth to work so I'm VERY familiar with
that vehicle) is a faulty Frequency Valve C which causes this symptom. I
replaced the original one around four years ago with a used one(around $40)
from Matta Motors(www.mattamotors.com). When I bought it they confirmed that
it was a very common problem and were very familiar with it. It was fine
until a year ago and then it would again occasionally refuse to kick down to
normal idle speed....racing at 2000+ rpm when in P or N. I've found that
smacking the side of it several times with a wrench works wonders

It's the small, black cylinder-shaped thing on the passenger's side(mounted
in the fender well) in the engine bay. It's located directly under the
fusebox and it has TWO vacuum hoses going to it.