2004 WRX wagon, 117k miles Stage 2 Stock intake / filter Probably about 10k miles ago I started to have issues with the engine dying on warm starts, while the transmission was in gear (clutch in) during parallel parking, and even shifting at speed with the clutch in around corners... on freeway interchanges when it got REALLY bad. I don't need to tell you guys how unsafe this is due to power steering loss, etc. :eek3: I brought it into Morrie's and the first couple times they couldn't figure out what it was, blamed it on the tune, etc. I tried cleaning the IACV myself + new gasket, which mostly fixed the problem, but then it got worse again. Finally a Morrie's guy took stuff apart and found that the throttle body was carboned up and the IACV was in bad need of cleaning. Cleaning both fixed the problem completely!! :biggthumpup: Everything was fine for a couple thousand miles, until I was coming back down from Pike's Peak and the whole thing started back up again (mildly). That was 2k miles ago and it's gradually getting worse, like it did before. :emo: Here's my question: What would cause the throttle body & IACV to get carboned up in the first place? I could clean the throttle body & replace the IACV, but I don't want to do that yet if this problem is just going to keep coming back for some other reason. Ideas?
Check for excess blow-by in the turbo inlet, PCV lines and y-pipe. I don't know what else could jam up the IACV and TB so quickly, unless the air filter is shot. ~Dan
Should have double-quoted, but here I am... ScubaSteve cleaned my MAF sensor before when I had it at his place for engine mount replacement, and that didn't do anything. PCV... sorry, can you remind me what that stands for? Still a newbie in many ways.
Cleaning the MAF won't change the cleanliness of your TB and IACV. PCV is positive crankcase ventilation. Basically, as the engine heats up and you generate boost and such, the engine (crankcase) develops excess positive pressure that needs to be released. If the excess pressure isn't released, the engine doesn't work as efficiently. Since the crankcase contains oil, the excess air pressure mixes with the oil. The oil+air mixture is dumped into the turbo inlet and mixes with fresh air and goes back through the throttle body and IACV. This excess oil+air mixture is known as blow-by. The PCV system helps the engine breath while not in boost and while idling. Part of the PCV system controls and carries blow-by. Here's a helpful link that explains how the engine works while under boost and during boost. It also explains different catch can setups. http://www.iwsti.com/forums/2-5-lit...e-venting-o-separators-catch-cans-thread.html ~Dan
OK. Skimmed through the STI PCV reading... Since I'm only at Stage 2, would it be safe to assume that I probably just need to replace my PCV valve, and not necessarily install some sort of catch can? Am I right in thinking that the stock setup does NOT have an oil catch can?
On every 04-05 I seen, there is no PCV valve, it looks like one but is just a free flowing orifice tube.
