Has not been idling properly?

ANONYMOUS

MEMBER
1999 MITSUBISHI GALANT
16,200 MILES

I own a mitsubishi galant GDI 1834 cc. Recently the car has not been idling properly. At start up the car will rev to 2000 rpm and when drive is engage it will drop to 600 rpm. The idle speed will then fluctuate and it will shut down, it is even worse if the AC is on. It constantly shuts down but will restart immediately. I had it checked and I was advised to change the air flow sensor and the oxygen sensor and clean the throttle body including the idle sensor. I have done all these things but the problem persists. Is it the high pressure pump on the engine head? The car accelerates fine on high speed and there is no reading on the scan tool for the pump. Please advise

1 Reply

SQM

MECHANIC
6,383 POSTS

Hello,

It sounds like the idle air control valve is likely bad.
You have cleaned it, which can help if the issue was triggered by being dirty component. But if the stepper motor of the idle air control valve is bad then it will also have similar impact on the idle.

https://www.2carpros.com/articles/how-a-idle-air-control-valve-works
https://www.2carpros.com/articles/idle-air-control-valve-service
https://www.2carpros.com/articles/how-to-replace-an-idle-speed-control-motor-iac

Test the IAC stepper motor by checking the resistance.
I have include diagrams that shows how to test the motor and other components of the IAC.

Please let me know of any questions.
Thank you.

Images (Click to make bigger)