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howdy all i have a 1998 wrx wags and i have been having the(apperantly common) problem of losing revs, choppy idle,almost stalling then picking up revs again,loss of power/bogging down when accelerating. then it will run fine for a while sometimes days sometimes mins. mods so far are: front mount,bov,cat back,pod filter,boost controller,turbo timer, light weight pulleys. after reading some threads on this forum i pulled off and cleaned the throttle body, idle air control valve(new gaskets for both), air flow metre, o2 sensor. and it still runs crap. while removing the o2 sensor i had to take off the heat shield for the turbo and i noticed some carbon deposits on the inside of the shield so i'm guessing a leak from the gasket. would this be causing the problem to go on?
any help/advice would be greatly appreciated.

cheers

rob

Is it producing any engine codes via your check engine light?
Despite cleaning the air flow meter that could still be the problem, they can certainly produce those symptoms even without producing an error code. Might be an idea to ask a favour from someone and borrow a known working one to try out.

Mmm, AFM's are a know problem with that model.

full atmo bov (most cheep ones) will do it every time or yeh afm

yeah it is a full atmo bov(turbosmart type 2 v-port) but that was on the car b4 this problem came about.

i un-pluged the afm while the car was running and it ran even worse so i dont think its that

a guy at profix said that the idle air control valve is stuffed, subaru want $750 for a new one is there any cheaper options(second hand, aftermarket, ect)

cheers
rob

drako wrote: a guy at profix said that the idle air control valve is stuffed, subaru want $750 for a new one is there any cheaper options(second hand, aftermarket, ect)

Very possible - borrow a known working one to find out for free.
If it's the problem yeah, source a good secondhand one, unfortunately there is no cheap option for brand new. Another thing you could try it spraying it out with upper engine cleaner, sometimes they just foul up.

drako wrote: i un-pluged the afm while the car was running and it ran even worse so i dont think its that

This proves absolutely nothing, a faulty AFM will still run your car better than none at all.
It still could be the problem - borrow a known working one to find out for free.
If it's the problem best bet is to source a good secondhand one, you will be unpleasantly surprised by Subaru's pricing on these too I expect!

By the way just had another thought, I've had similar problems to your description too and in my case it was bad injector seals. The rubber O-rings weren't sealing properly. Hard to test for without removing the injectors and replacing though. More food for thought.

AFM- i went on the same witch hunt with my wagon, is your pod filter a oiled type like K&N?

yeah its a trust ram air podfilter

I had the same problem with an MPFI L series, and it was the idle air control valve, pretty easy to diagnose though, just block it off to see if the idle steadies. I think they are closed when engine is at operating temp??