[sfortin]

So, when I do a hard acceleration I lose power when I reach around 4500 RPMS or so.
It feels like if I’m red lining at those RPMS and that the car wants me to shift. The car starts jerking back and forth like if gas is coming in and out.
If I do gradual acceleration, I have no issues.

To try and troubleshoot this I have changed the spark plugs, fuel filter, fuel pump.
I have no engine codes and checked with OBD sensor with no avail.
Any suggestions?

 

[MainFrame]

Is the car 100% stock? Is this something it just started doing, or has it been doing it for a long time? Did it start suddenly out of no where, or had you done something to it prior to the issue?

 

[mycologist]

tag for later

 

[sfortin]

i bought the car used not even 6 months ago.
It is stock and it use to do it every once and a while and now it seems to do it all the time.
So, problem has gotten worse in a short period of time.
NOw, seems to do it even at lower RPMS. Sometimes in the 3400 as well. usually in 1st or second gear.
When I downshifted on the highway, did the same in higher gears.

 

[sfortin]

sorry to ask, but wouldn't a faulty coil pack act up at all rpms and probable cause engine misfires?
My coil packs failed on my jetta (sorry to cheat on the wrx) and I got misfires.
engine light would flash. Doesn't Subaru act the same?

 

[sfortin]

I did find this information on another forum (not to cheat on this site, you guys are great, but its based on having more info to help others)

WRX Detonation Cause FOUND! (Datalogs Included) - NASIOC

If anybody has seen this happen to their 2002- 2004 car the ECU is stated to have some issues at fast spooling of the turbo and the Subaru ECU not having proper AF ratio configured.

Anybody have this info or similar that could share this would be awesome.

 

[MainFrame]

..wouldn't a faulty coil pack act up at all rpms and probable cause engine misfires?
My coil packs failed on my jetta (sorry to cheat on the wrx) and I got misfires.
engine light would flash. Doesn't Subaru act the same?

A failing coil pack could certainly cause misfire.. but not always (or at least not always detectable to the ECU). Usually a misfire will be accompanied by a flashing CEL, then there may or may not be a code stored in the ECU describing which cylinder the misfire was occurring on.

I did find this information on another forum (not to cheat on this site, you guys are great, but its based on having more info to help others)

WRX Detonation Cause FOUND! (Datalogs Included) - NASIOC

If anybody has seen this happen to their 2002- 2004 car the ECU is stated to have some issues at fast spooling of the turbo and the Subaru ECU not having proper AF ratio configured.

The delay in switching from closed loop to open loop fueling described in that thread was a problem that popped up in the 2004 year model when the ECU was changed for the new model. Bugeye WRX generally don't have that problem.




For what it's worth, I had an issue with my 02 WRX for a long time where it would stumble and lose power as soon as the boost pressure reached about 14psi.. and it was not able to achieve boost higher than 15psi even though it had a manual boost controller and was tuned for 19psi. There was never any check engine light, and no misfire was recorded. Data logs looked normal until the boost pressure reached that point. There was nothing clear in the data logs that indicated a problem with anything.. other than the rpm became erratic and it couldn't produce any boost past 15psi. I finally was able to trace that down to a failing coil pack. I would guess that it wasn't getting a strong enough spark on that cylinder and it was blowing out once the boost reached a certain level.

My issue was boost pressure dependent, not RPM. As long as I didn't press the throttle hard enough to hit 13-14psi I could rev it all the way to redline without stumbling. That sounds like it could potentially be your problem since you said if you accelerate gradually it doesn't happen.