Impreza spitting white smoke

[AlmightyBirdman]

So here's the story: Two of my friends have Imprezas, one has an 03 on has an 05. The friend with the 03 is selling his soon and switched exhausts with my friend with the 05 because he wanted a quieter exhaust and to make some money before he sold his car. So yesterday they switched exhausts, and for some reason when they bolted the exhaust onto the 05 and started it up it was spitting out white smoke and smelled like gas indicating it was running lean. Now my friend with the 03 has never had any problems like that with this exhaust. So we decide to put on the cat to see what happens(it was just straight pipes from the turbo back to the muffler before), and the same thing happens. We think that it needs a tune but a dyno tune at AMS is $$$$$ so I figured I'd ask before he got it tuned if anyone else knew why it's running lean. tia.

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[Mook]

i take it these are both wrxs?

 

[AlmightyBirdman]

Yes we just thought it was weird that when the 03 had it on it was normal but on the 05 it runs lean. We don't know if the 03 was tuned or not though it was bought modded.

 

[Spicy McHaggiz]

IF it is untuned and it has an aftermarket turboback exhaust then it needs tuned ASAP because its running lean as hell. 02-04 had pretty touchy ECM's so something that simple would cause it to run lean.

www.nasioc.com

 

[AlmightyBirdman]

Yeah we figured it was that he needed to be tuned, I can't remember if the car that it's on now is an 04 or 05 so it must need to be tuned if the 03 it was on before had no problem.

 

[Mook]

did they do a hard ecu reset after they put the exhaust in?

let the ecu try and relearn w/ the new exhaust on it. those ecu's arnt that dumb, they should be able to recalculate fuel for whats happening. im not saying the car doesnt need a tune, because that would help it out greatly, but it just seems odd that it would be affected that much.

not sure what else it could be. maybe take the maf out and clean that up, make sure its getting a good reading of air coming into the engine

 

[AlmightyBirdman]

Yeah I'll talk to him about that today, thanks mook.

 

[Spicy McHaggiz]

Mook a "hard reset" on the ECU won't compensate for a complete turbo back exhaust on these cars.

 

[Mook]

i would think it enough to keep it from running super lean....surely it cant be THAT much worse than other turbo cars

 

[Chrisco]

Define lean, because you aren't using terms correctly here based upon the symptoms that you've described. If you can smell raw fuel coming out of the tailpipe, that means it's running RICH. Considering most cars (i can't say every because I know it'll bite me in the ass) are tuned rich from the factory in WOT conditions, I don't see how not tuning the thing is going to hurt anything.

It sounds to me like you and your friend are confused.

Also, if you're seeing white smoke and you're sure it isn't just water vapor then you have something wrong completely unrelated to an exhaust issue. White smoke = burning coolant, which would give off a sweet maple syrupy aroma. Blue-Bluish white = burning oil. Black smoke = too much fuel = rich. A lean mixture isn't going to produce any coloration in the exhaust unless it's at the point where you already melted something in the engine and now you're burning coolant/oil.

With the car running at idle, put your hand behind the muffler a couple inches away and tell me if you see little specs of carbon/water getting splattered on your hand. If you are, it's running rich, not lean.

 

[Mook]

i didnt even read the part about smelling like gas

 

[Chrisco]

Mook a "hard reset" on the ECU won't compensate for a complete turbo back exhaust on these cars.

If putting an exhaust on throws the AFR's off THAT much, then it's going to throw a code and cause the check engine light to come on. I highly doubt that's going to happen.

However, i know that Subarus have 2 sets of cats, was one before the turbo in the stock manifold? If they're all after the turbo and you removed them all, then the car is definitely going to run like shit, but it'll be running like shit rich, not lean.

 

[Mook]

agreed

 

[AlmightyBirdman]

doh! I meant to put running rich my bad guys. But when he revs it up it spits white smoke out and smells like straight gas.

 

[Spicy McHaggiz]

If putting an exhaust on throws the AFR's off THAT much, then it's going to throw a code and cause the check engine light to come on. I highly doubt that's going to happen.

However, i know that Subarus have 2 sets of cats, was one before the turbo in the stock manifold? If they're all after the turbo and you removed them all, then the car is definitely going to run like shit, but it'll be running like shit rich, not lean.

02-05 Subaru used a cat pre turbo in the "up pipe" and then 2 cats post turbo. One in downpipe and one at the tail end of the downpipe.

And the CEL is true if the car hasn't been touched by a tuner before. If one of these cars has a Cobb AP tune on it, even a stage 1 which would be for a single downpipe it completely disables the CEL for cats.

 

[Chrisco]

doh! I meant to put running rich my bad guys. But when he revs it up it spits white smoke out and smells like straight gas.

smelling like straight gas and white smoke still don't go hand in hand.

 

[IDAFC21]

you sure you guys didnt bump an oil and/or coolant line loose on the turbo when you were bolting up the downpipe or something?

 

[AlmightyBirdman]

I'll have to ask them, but yeah it is really weird.

 

[Stink Star]

If one of these cars has a Cobb AP tune on it, even a stage 1 which would be for a single downpipe it completely disables the CEL for cats.

it disables the CEL for the post cat 02 sensor... the engine still needs an accurate signal from the first 02.... thats how it determines how much fuel to add. if a cobb tune disables that, then that is the worst tuning company in the history of the world

 

[Spicy McHaggiz]

it disables the CEL for the post cat 02 sensor... the engine still needs an accurate signal from the first 02.... thats how it determines how much fuel to add. if a cobb tune disables that, then that is the worst tuning company in the history of the world

Maybe we didn't read the same thing but I said it disables the CEL for not having any cats on the car. Obviously it still uses the first O2 to "tune" the car.

 

[WhiteDevil]

Im with chrisco on this one, lean is lack of fuel, if you are smelling fuel then you are rich. what else did you guys touch under there?