What's wrong ? - RPM's rise & fall @ idle only

[Legacy Wagon]

Car is a '91 Legacy Wagon LS 5sp

This is something rather new. Started about 1.5 months ago . At first it was just a little annoying but lately its caused my car to stall every so often so its a PITA now. What happens is when the car is left to idle , sometimes the rpms with go up & down and on the down the car damm near stalls or will stall. Happens without ryhme or reason, sometimes it does it sometimes its just fine. Doesn't seem to matter if its -5 or -35. Doesn't matter if I just started the car or if I come to a stop after 30 mins driving on the highway. Other than that the car runs excellent, it revs freely, never hesitates and fires strong up every time when stalled.

I will say that in late Nov one of the exhaust pipes cracked where the two front pipes from either side of the motor join right before the cat. It ran fine for over a month this way so I'm not entirely convinced that's the problem though it very well may be. Suggestions ?

Watch the video below I took in the driveway. THat's all the car, not me screwing with the gas pedal. Sorry for the small size, thought it was filiming @ 320 but ended up at 120.


http://vortex1.no-ip.com/tex/subaru...pm/MVI_1477.AVI

[Legacy777]

probably your IAC valve sticking.....there are a few threads here on how to clean them. Ciper has done this many a times with success.

[legacy92ej22t]

It sounds like your IAC solenoid valve is going bad or is maybe sticking.

With the engine cold, turn the key to "on" but don't start the engine. Check for battery voltage on the electrical connector on the harness sides middle terminal. Also check the resistance on the IAC valve side. Check terminal 1-2 and terminals 2-3. Both should have 9 ohms. If either check is open or short then the IAC valve is bad.

If you have battery voltage and the correct resistance on the IAC valve then start the engine and allow it to warm up. Once it's warmed up, turn the engine off, remove the IAC valve and check to make sure the shutter is completely closed. If it's open then the IAC valve is bad or sticking. You can try to clean the shutter with some good brake cleaner and put it back in and see if it helps. If not then it's time for a new IAC valve.

I hope this helps.

Oh, that link you have there didn't work for me.

[legacy92ej22t]

Haha, Josh. You must have posted right as I started to type my responce.

[Legacy Wagon]

Good stuff guys, I'll try this on the weekend. Matt - Can you point me to somethign that has pictures to show 1st where the IAC is and then which terminals are whcih ? Cheers !

Alexxi

[Legacy777]

pics of IAC, and other misc engine sensors

http://www.main.experiencetherave.com:8 ... P_2470.JPG

http://www.main.experiencetherave.com:8 ... injectors/

[legacy92ej22t]

Good stuff guys, I'll try this on the weekend. Matt - Can you point me to somethign that has pictures to show 1st where the IAC is and then which terminals are whcih ? Cheers !

Alexxi

Hmm..I don't have any pics of one on the car. It's on the passanger side of the intake manifold, down low kind of towards the firewall. It has a couple hoses running into it, one larger and one smaller. IIRC, the larger one is an air hose and the smaller one is a coolant line. At the top it has an electrical connector that connects to the side of the top.

In terms of the terminals, there's only 3, kinda like this [321]. Check the middle one on the harness side for battery voltage. On the IAC side check the one on the left and the one in the middle (3-2) for 9 ohms , then check the one in the middle and the one on the right (2-1) for 9 ohms.

Hope that helps.