Messed up idle

[Ghost]

Note: I have searched threads on high idle, and I plan to attack the TPS, ISC and double check for leaks.

I sort of had these following symptoms before, almost always when the engine was cold. I recently changed the plugs and wires for OEM spec NGKs (I disconnected the battery for a couple hours while doing this). This has made the symptoms many times worse. But besides that nothing is obviously wrong, and the new plugs had a very positive effect on response under boost. When I'm flogging the car it feels happier than ever.

Whenever I touch the gas the EFI system is really reluctant to let the idle drop. It will hang at whatever RPM I released the throttle from for a couple seconds. If the car is coasting, I can feel that there is no engine braking, if I push in the clutch it hangs for a couple seconds then will drop over a couple seconds, sometimes hanging a little above 2000 rpm for a moment.

Driving around with this is like having somebody flicking your ear repeatedly. It is maddening.

So I was thinking maybe the ISC is gunked but after reading around that seems like a bad thing to clean out. I figure the set screw on the throttle is okay, and that the throttle plate is closing all the way, otherwise it wouldn't gradually lower. And yes, the throttle snaps closed. What do you guys suggest, what should I start with?

[Legacy777]

Has it always done this or is it something that recently started?

One you can check on the IAC valve is remove the electro magnetic head (mark its position so you can put it back the same way) and see if the valve portion spins freely. If it does, then the IAC should be ok.

Are the symptoms worse when the engine is "cold" vs. "hot"?

Does your throttle body have one of these bypass needle valves?

http://www.main.experiencetherave.com/subaru/images/tb/

[IronMonkeyL255]

If it has one of those bypass needles, I would suspect that. I had the one on mine back out after not touching it, and it was causing similar issues. Was driving me crazy trying to figure it out, but once I did I loc-tited it in place when I set it.

Also, there should be a way to check if the idle switch in the TPS is being triggered. There is a specific switch that gets triggered when the throttle if fully closed. I can't seem to find the way to check it right this moment, though.....

[Legacy777]

Here's the info on how to check the idle switch.

http://www.main.experiencetherave.com/s ... sting3.jpg

Other scans with info on which pin is which
http://www.main.experiencetherave.com/s ... sting1.jpg
http://www.main.experiencetherave.com/s ... sting2.jpg

[Nibbib]

I have that same issue lol but it didn't have it when I first got the car more around when summer started here in oregon