Idle Up

Gentlemen, I need assistance on an idle thing with my 1989 S-10 Blazer.

Here is the input info. on the idle problem.

1. Miles on vehicle is 80,000.

2. Problem hss been around since fall of 2009.

Here is what happens.

1. Start engine warm or cold.

2. Engine goes up to say 1100 rpm and holds this for say 5 seconds.

3. After the 5 seconds, the engine speed ramps up to say 1500 rpm for say 4 seconds and then ramps down to say 1000 rpm for a cold engine or to 750 rpm for a warm engine.

The following items have been done:

1. Replaced the throttle body gasket.

2. Examined vacuum hoses for leaks.

3. Replaced some vacuum hoses (due to age).

4. Examined the TPS and checked with multimeter. OK.

5. PCV valve cleaned and ok.

5. Removed and cleaned IAC valve. Cleaned the carbon from the pintle and throttle body seat in housing. Side note guys-the pintle appeared to have carbon deposits (soot) on say 80% of the circumference. The remaining surface area of the pintle was clean. Does this indicate the pintle is seating correctly?

Your suggestion will be appreciated. Thanks.

just one question, did they still put dash pots on the idle mechanism in this year? If so, you may want to check that. the high idle is dependent on engine temp, so find out how the temp sensor mechanism works, and see how it is failing. do you have a repair manual?

No dash pot on this throttle body unit. I do have a Chevrolet repair manual. I will recheck the water temperature sensor. Thanks.