Loss of fluctuation of RPM while the car is cold or warm

TAHIR ULLAH DAWAR

MEMBER
1999 TOYOTA COROLLA
4 CYL
2WD
AUTOMATIC
100,000 MILES

Initially my car rpm used to be at 1,100 when cold and at about 600-700 when warm. But from the last month the rpm is at about 800 when cold and remain almost at 800 when it gets war. Thanks

Thursday, September 13th, 2018 AT 7:54 AM

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi and thanks for using 2CarPros.com.

The first suspect I have is the idle air control valve (IAC). The IAC is responsible for maintaining the engine idle speed. Here are general directions for replacement. What I would like you to do is remove it and inspect it for carbon, function (have a helper turn the key on and off while you check for movement,) and if the air way is blocked with debris.

https://www.2carpros.com/articles/how-to-replace-an-idle-speed-control-motor-iac

I attached a picture of the IAC location. It is component I-1.

Check this and let me know what you find.

Take care,
Joe

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Thursday, September 13th, 2018 AT 7:53 PM

TAHIR ULLAH DAWAR

MEMBER
1 POST

Thank you so much.

I was also suspecting that but few days ago a mechanic opened and cleaned the throttle body, spark plugs and also the radiator. Is it not the fault of cool temperature sensor which is always sensing as warm even if cold? Waiting for much helping advice. Thanks

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Sunday, September 16th, 2018 AT 1:03 PM

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

Did he clean the IAC which is different than the throttle bore? On these cars the IAC gets stuck causing the engine to stay at one idle, but the engine coolant temperature sensor can cause this as well. Here is a guide to help walk you through the steps and the location for the sensor for your car below:

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

Check out the diagrams (below). Please let us know what happens.

Cheers, Ken

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