high idle rpm in manual tran Legacy... why?!?! [Archive]

mwmtlm92

10-27-2006, 08:36 PM

Need some suggestions pls. Here is the story...

1992 Legacy manual. 74k miles.

Just recently, the engine rpm races to ~2000 rpm when putting in the clutch. Mostly happens when engine is warm. Somewhat intermittent.

Never happened before. Any ideas?

Thx in advance!!

Wiscon_Mark

10-28-2006, 03:56 AM

Clean out the IAC valve, or even replace it. Try a tune up. It's probably something minor.

Durs845

10-29-2006, 04:44 PM

probably IAC , mines idleing all screwy 1800-2200 constintly up and down , regardless if the motors warmed up or not.

warrior

10-31-2006, 08:30 AM

probably IAC , mines idleing all screwy 1800-2200 constintly up and down , regardless if the motors warmed up or not.

This was a HUGE issue with Eagle Talons/Eclipses (my first car) It was always the IAC valve, there was no code for it when it stopped working. The computer would register too much air so it would increase fuel, when rpms go up, it was register rpm to high, cut fuel.. hence the surging up and down.

It may not be the same with Subaru's but all and all, it's most likely that.

smoke3006

10-31-2006, 11:12 AM

Stupid question:
What's the IAC and where is it located?

I did search but I didn't find specifics, sorry.

Wiscon_Mark

10-31-2006, 11:15 AM

It's on the throttle body.

That large line the goes directly from the intake tube into the intake manifoldish/throttlebody area is the Idle air bypass line. The IAC valve is in there.

jey

11-05-2006, 01:23 AM

probably IAC , mines idleing all screwy 1800-2200 constintly up and down , regardless if the motors warmed up or not.

This was a HUGE issue with Eagle Talons/Eclipses (my first car) It was always the IAC valve, there was no code for it when it stopped working. The computer would register too much air so it would increase fuel, when rpms go up, it was register rpm to high, cut fuel.. hence the surging up and down.

It may not be the same with Subaru's but all and all, it's most likely that.

Mine does that if the idle adjustment screw is adjusted to too high. And like warrior said, what happens is that the computer would increase fuel up to a certain point, and then cut it, causing the surging up and down.