Idle raises to 2500 rpm when car is very hot

you forgot to say hot or cold engine so is 2 answers.
they had 3 engines that year (the nn = liters)
G16, 16valve i4
j20 dohc i4
H27 v6
nobody on earth can guess the engine, and is an engine question
2000 is 100^% normal on any cold engine, 1500 to 2500 range cold
based on coolant temps -30f to 180f.
the colder it is at starter the faster the idle, and is AIC controlled
when hot the engine ecu goes to full hot (normal ) engine rpm controls using the ISC.
the exact parts are not the same on the 3 engine ever.
next time tell engine and if RPM is cold engine or hot.

btw I owned all 3 cars before, so have full documentation on them.
and restored them too. and can field most questions.

The throttle position sensor may be causing your issue----This sensor monitors the outside air temp.In the winter the throttle opens up far because th.e air temp is cold and vice versus

55 is max (pressure relief)
20 is typical hot engine at 800 idle. and rises as RPM rises.
your post tells neither , temp, or RPM

could be a air pockets in the coolant system that have top bled out
it is a simple exercise to have a compression test done to check for head gasket or cracked head

which car is it?

problem with 1993 Geo Prizm '99 silverado 5.3 engin will not idle runs at 2500 rpm and drops down to 1000 rpm the back up to 2500 rpm -------------------------

this is what i found about code f85




QUESTION: 1991 Sedan Deville, 4.9 port injection
Car runs great until outside temp reaches 92 deg. or above. the car will start to cut out under load (take off or hill. if i pull over the car will idle fine rev the engine to a steady high rpm and it will cut out. i had a code e44 (o2 sensor rich)so i replaced o2 sensor with no effect. the other code received was f85 (Throttle body service required). I have checked all connectors and hoses attached to the throttle body. all ok. looking inside throttle body there ar two tubes under the flaps one is totaly restricted with a black buildup and the other partly blocked. Not sure what these tubes do and if that could cause engine to cut out when hot and under load. any ideas?

ANSWER: You found your problem which is this black residue which when hot turns to a jelly substance and blocks the idle air passage. You need to clean all that residue from the throttle body and do not forget to spray the small hole in the side of the throttle body just behind the throttle plate.

Could not agree with you more - was thinking that it was a circulation problem with coolant when you mentioned your suspicions.

clean your map sensor first not reading air temp

I would probably start by replacing the upper hose. The temperature guage and heat will be affected by poor circulation of coolant.

This sounds like you have a pcv hose that has become an open vacuum leak. It is located under the upper intake, or given the year your air filter box may not be correctly sealed and possibly have a mass air flow sensor concern. Any Check engine light or codes to work with ? I f you have further questions just leave a comment on my page,