Honda Repair: surging idle in hot weather, honda civic dx, air control valve

Question
I have a 1990 manual Honda Civic DX with ~109,000 miles on it.  If the outside temperature is above 85 or so and the engine is warmed up, the idle races badly when i'm not in gear - i.e. stuck in traffic, waiting for a light, etc.  If i don't start moving the car, the idle goes faster and faster and then suddenly stops, and it feels as if the car is about to stall, but it doesn't.  The racing idle is accompanied by a lot of heat - the gearshift feels hot, the steering column feels hot, and the key is hot when i finally do stop the car - but the temperature gauge doesn't show any abnormal heat at all. I took it to a honda dealer who replaced the radiator fluid, after telling me that there were "bubbles" in what i had in there (?) and it seemed a little improved but was not fixed.  There are no problems in cooler weather. Any advice is appreciated.  

Answer
Kathy,

Wow that's a tricky one. The first thing I would check is the throttle cable. You need to have it adjusted. Have them put some slack in the cable at the throttle body. I have seen quite a few of those cables for some reason "shrink"? That could be causing the high idle. You may even be able to do it yourself. It;s not hard to do.
Also check your floor mat. Sounds wierd, but sometimes they get caught on the gas pedal,and cause the pedal to be depressed, thus raising the idle.Another thing is the IACV (idle air control valve) If your valve is bad, it may cause this also.
In any case, this is a serious saftey concern. You can imagine what can happen if your idle creeps up while waiting at a light. You should get this problem resolved quickly.
Good luck and thanks for the question,
gene