05 wrx rpm issue

[Zach]

Hey guys my friend owns an 05 wrx and reacently he started experiancing a problem with the rpms. Pretty much what happens is when your in 3rd/4th gear and you got WOT the rpms get to 4k then instantly drop to 3.5k and then the rpms climb like nothing was ever wrong. Anyone have any ideas what it might be? I know an internet diagnosis is hard with out seeing the car first hand, but where just trying to get pointed in the right direction.

 

[i-wagon]

Stock? Tuned? I'd wonder if it's losing fuel in that rpm range maybe tweak a tune. Fuel pump getting old? Right one for stage of tuning? Cel maybe?

 

[Zach]

My friend hasn't done anything to the car other then cosmetic stuff since hes owned it but as far as I know its got a 3 inch DP and is suposibly stage 1. I also noticed that his bosst is pretty high hitting 18-20psi some times which is higher then my car and its stage 2.

 

[RyanR]

Sounds like overboost (resulting in fuel cut) under high load in that rpm range, which makes sense if he is running a stage 1 tune with a downpipe. Now that the temps are dropping, it's much easier for it to occur.

I can help point you in the right direction remotely if he can post up logs of the issue occurring.  However, I still recommend you let someone with mechanical/tuning ability actually lay hands on it.

Log the following values:

Engine Speed
Engine Load

Feedback Knock Correction
Fine Knock Correction

IAM

A/F Learning #1 (%)
Manifold Relative Pressure (corrected)

Wastegate Duty Cycle
Target Boost
Injector Duty Cycle

Mass Air Flow (g/s)
IAT
Wideband o2 sensor if he has one (and he should)

My advice to him is to stop driving the car, or to stay out of the boost until this is sorted out.  I realize on one hand I'm telling you to post up some logs of it happening, and on the other telling you to just take it to a tech.  I'm trying to offer you options, in the event that he doesn't live around a competent tech.  If you tell us where he is located, we might be able to recommend someone he can go to.

 

[Ryan]

I would do some general maintenance stuff such as replacing fuel pump and filter. Clogged injectors might do it too.

 

[Zach]

Sounds like overboost (resulting in fuel cut) under high load in that rpm range, which makes sense if he is running a stage 1 tune with a downpipe. Now that the temps are dropping, it's much easier for it to occur.

I can help point you in the right direction remotely if he can post up logs of the issue occurring.  However, I still recommend you let someone with mechanical/tuning ability actually lay hands on it.

Log the following values:

Engine Speed

Engine Load

Feedback Knock Correction

Fine Knock Correction

IAM

A/F Learning #1 (%)

Manifold Relative Pressure (corrected)

Wastegate Duty Cycle

Target Boost

Injector Duty Cycle

Mass Air Flow (g/s)

IAT

Wideband o2 sensor if he has one (and he should)

My advice to him is to stop driving the car, or to stay out of the boost until this is sorted out.  I realize on one hand I'm telling you to post up some logs of it happening, and on the other telling you to just take it to a tech.  I'm trying to offer you options, in the event that he doesn't live around a competent tech.  If you tell us where he is located, we might be able to recommend someone he can go to.

He lives in Monmouth like 300 feet down the orad from me. I told him to either go see Mike or go to M&A auto in Lisbon, but I can only tell him so much its up to him to make an appointment.

 

[Zach]

So He got it checked out by M&A Auto and I guess they found a vacum leak, larger then stock injectors, aftermarket catless uppipe,  and an originally catless downpipe with a cat welded into it and I guess it was already running a stage 2 tune. They also said at one point it looks like their was a larger turbo because the stock one that's on their now is not in the correct location.