RPM Idle Dip

[Tedpro]

Hello,

After a recent Rally X my 05wrx.
Whenever I rev up the engine a little bit either from and idle or from driving, when it comes back down it dips anywhere from 200-400RPMS, and is steady idle at about 600-700RPM.

Could this be a result of a dirty airfilter/O2 sensor(err I meant MAF)?

[Gravel Crew Rally Team]

I would say to clean/check your air filter and spray off your MAF sensor. Use electrical cleaner or find and actual MAF cleaner, you can go to pretty much any parts store and find those. o2 should be ok.

[Tedpro]

I replaced air filter, and still same issue.

Going to clean MAF soon.

I saw this review : http://forums.nasioc.com/forums/showthread.php?t=781242

Could this being dirty/bad gasket be causing my issue as well?

[Tedpro]

So I think I have a vacuum leak.
With the hood open, and revving the engine. I hear a short sucking sound coming from engine sometimes.
- it happens right after the idle dips the lowest , I hear the sound , then RPM comes back up to proper idle.
Is this a vacuum leak or something else?
Will this ruin my car? I've been driving like this for a bit now.

Swapped MAF & airfilter , not the issue.

[trastrim]

You accidentally the whole air leak? Is this safe?

[Tedpro]

I saw on a couple websites that replacing the PCV valve might fix this.
I still have not cleaned the IACV yet.

[T-Heineken]

I cleaned my IACV and replaced the gasket and it helped when I was having issues with idling (almost to the point of stalling).

You can just let the whole top piece soak in a wee bit of petrol...now that'll clean it right up!

[Tedpro]

How long did you let it soak?

[Tedpro]

So issue seems to be fixed, I saw a post on a different forum that some guy had put seafoam in his BOV[recirc in my case] vacuum hose to clean out the IACV(I was not able to get the 2 screws off, and didn't want to strip them). After sea-foaming and driving car around it seems to have fixed the issue. As for the leak sounds, it may becoming from the up-pipe gaskets as I am missing some of the bolts from there.

[Jesseshawkins]

I'm hoping to revive this thread maybe, and this may be a dumb question. I did a search and returned nothing. Im having this exact same problem on a tuned / rotated / dominator 3 2004 STi. Where is the IACV? on the throttle body? is there a procedure to clean it out?

I thought it was my MAF scaling and Ive gotten everything I need to do opensource ECU tuning but I need to nail down that everything else on the car is working correctly first.
Thanks guys.

[kreitz3]

I'm pretty sure all STI's in the U.S. are DBW and do not have an IACV.