Question about 1995 Mitsubishi Eclipse
I have searched this forum for idle problems and some threads have similar problems and good recommendations associated with cleaning or replacing the IAC valve. But, I would like to test my IAC valve before spending $78 to replace it.
My IAC valve was definitely dirty and sticking. After cleaning thoroughly it still has an idle problem when cold and in gear at a stop. It is idling around 760 out of gear and 560 when in gear and at a stop (unless it dies). The engine RPM was verified with a ProScan PC tool. One of the other threads indicated these are the correct idle speeds.
Sometimes though it does not seem to hold the 560 RPM idle in gear and the engine starts misfiring. It might drop to around an idle of the mid-400's. This is even after the good cleaning.
My daughter drives this car regularly and started complaining last week that when she put it in gear the car would die. Of course, it was about -9 deg F one morning it died and she could not get it started after it died. Kids these days don't know to press on the gas to help start or keep the car running. They expect the ECM to do all the work.
So, I still have the question "is my IAC valve bad?". Before cleaning the IAC valve I connected the coil to a variable power supply to test movement of the valve. I could not see any movement in the valve while changing the voltage from 0-12 VDC. It was also initially set to about 1/16" open and I forced it close with my finger. After cleaning the valve I ran the same test and could not see the valve move either. I could physically move the valve to different positions with a needle-nose pliers, but the voltage changes never move the valve position. I really thought the valve was broken, but thought maybe I did just not understand the true operation of the valve so I installed it. When I started the car it idled up to about 1200 RPM and then started working down to the 760 RPM as it warmed up. I am think it is at least kind of working. Or is the ECM using something else changing the idle speed?
Has anybody ever tried to test an IAC valve with a variable power supply?
It definitely has a freewheeling diode in it, because it has to be connected in the right polarity to the power supply.
Any feedback would be appreciated.Hate to say it but a 16yo IAC valve is probably ready for replacement. You also can't test those things with constant DC voltage, im surprised it even still works. It gets a PWM signal from the PCM.
They aren't really supposed to be cleaned according to Ford, and those symptoms you mention are consistent with failure. Cleaning in my experience is a stop gap measure until it finally goes. I've had some luck by putting some oil on the shaft, can't hurt to try. I have one in my 95 that improved with cleaning and a few months later is starting to have occasional idle trouble.
Another thing you can try is cleaning the throttle body butterfly. I use a spent toothbrush, try not to get cleaner in the side seals.
Check rockauto (also look for a 5% discount code by searching) and you can probably get away under $50 aftermarket. The Motorcraft one is about 72 shipped after discount.
I would change it, you don't want it crapping out in an intersection.
Posted on Aug 13, 2012
a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
Posted on Jan 02, 2017
Tips for a great answer:
Jul 26, 2016 | 2003 Nissan Pathfinder
Jun 12, 2016 | 2006 Nissan Sentra 2.5
Nov 22, 2015 | 2000 Ford Ranger SuperCab
Sep 28, 2015 | 2005 Nissan Altima
Jan 20, 2015 | Cars & Trucks
Nov 12, 2014 | Cars & Trucks
Oct 17, 2014 | 2005 GMC Yukon
May 14, 2014 | 2003 Kia Sedona
Apr 23, 2014 | 2005 Ford F-150 SuperCab
Jun 04, 2013 | 2008 Volkswagen Eos
Aug 13, 2014 | 1995 Mitsubishi Eclipse
210 people viewed this question
Usually answered in minutes!
Step 2: Please assign your manual to a product: