Idle Air Control Systems - Idling continues


Asked by Dec 28, 2015 at 04:10 PM about the 1998 Mitsubishi Galant ES

Question type: Maintenance & Repair

I have a 1998 Mitsubishi galant es and it has failed
to pass inspection due to the Check Engine light
being on.  I have the idle air control system
checked [first] for leaks,  [second] replaced the IAC,
[now] throttle body. Still no change.

What else missing? Any wires needs
replacing/cleaning? Open to ideas.

8 Answers


Take vehicle to parts store like auto zone and they will read the check engine light for you for nothing. This will cut out a lot of guessing and tell you exactly what the problem is.

2 of 2 people found this helpful.

I agree. You may be barking up the wrong tree with the IAC. There's over 100 things that can trigger the check engine light. Post the trouble codes and we can help further. HTH. - Jim

1 of 1 people found this helpful.

@ firebird338 I went ahead and took it to the parts store for a reading. It came back with the original: P0505 'Idle Air Control Systems'. No further info on that. However, the person who looked at it also thinks it is "not" the IAC... It 'IS' a leak from somewhere out-of-sight.

1 of 1 people found this helpful.

Clear the computer, unplug the IAC, and start the engine. The check engine light will come on again because the IAC is unplugged so ignore it. If you get the P0505 code with the IAC unplugged the problem is in the wiring going to the IAC or the PCM (Computer) is bad. If you do not get the P0505 code with the IAC unplugged then the IAC is bad (shorted internally) and needs to be replaced. The engine will run and idle poorly with the IAC unplugged but it'll be just for testing purposes. HTH. -Jim

Best Answer

@ Js08016 Yes, I have been barking up the wrong tree. In addition to what I have mentioned to 'firebird338' post, I have learned that the hoses looked worn out; therefore, I will upgrade them when all this is cleared up. After they did the 'code check', the person blow smoke (smoker trick) into a line that would show the location of the leak, but his method was not strong enough to find it. He did use WD40 to try and locate the area while the car was running. I am positive that it IS a leak. I am have scheduled a full diagnostic to figure it out.

1 of 1 people found this helpful.

@Js08016 I will have him try that and let you know. As 'mechanically blond', I am learning something new every time. It is sad that I am learning the hard way. I appreciate it very much!

1 of 1 people found this helpful.

If you are getting a Idle Air Control code could be the gasket for the idle air control is bad and is sucking in air may just needs to be tightened down or replaced. To check for a vacuum leak would use carb cleaner or throttle body cleaner and spray around suspected area and motor will rev up if there is a leak.

1 of 1 people found this helpful.

@firebird338 Thank you! I will have those checked out! Much appreciated!

1 of 1 people found this helpful.

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