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02 Wrx Hesitation/bucking NEED HELP PLEASE

595 Views 0 Replies 1 Participant Last post by  Sprusinski
Hi all!
I have a 2002 wrx wagon with the following list of engine mods:
SPC air intake
grimspeed up pipe
sti intercooler
invidia downpipe
mishimoto lines
turbosmart multi function bov
manual boost controller peaking at 17 psi
and a "new" used td04 turbo
3in full catless exhaust

In the last 2000 miles I've done:
new plugs and coils
new bank 1 o2 sensor
speed sensor
cleaned air filter
cleaned MAF

For a few months I've had a problem with my car bucking/hesitating really bad when I get on the throttle. I've surfed through other forums many times but can't seem to find the exact problem I'm having. When making around 14 psi and at 1/2 throttle in second - fourth gear the car hesitates and backfires really badly around 4k rpms. I've replaced coils, spark plugs, cleaned the maf, reset the ecu, and o2 sensor to try and solve the problem but nothing has worked. The car also bucks slightly out of first and second but only when the car is cold (bad clutch maybe). The engine mods were done prior to my ownership as well as the tune. The previous owner says he experienced none of those issues, however. When I stay off the throttle the car behaves like a normal car until I get on it. My ideas are maybe fuel pump/injectors (although i ran injector cleaner through them a few tanks ago). Maybe a boost leak? I'm at a loss for what the problem could be. Any help would be appreciated. I'll include a video of the problem. You can see it's almost like the car hits redline at 4k when it's obvious it still has a lot more to go. Thanks for the help. The car hasn't thrown any cel's either.
I've also had a problem with the car stalling out after I was getting on it when the car is warm. I'll turn off the car and start it up again and it'll die unless I give it throttle. Not sure if that is connected or not.

WRX bucking and hesitation

I've talked to a reputable Subaru shop near me and the current hourly prices are out of my price range at the moment so I'm going to continue to try and diagnose by myself.
I replaced the MAF but am still having the same issues when I reach boost. I know that using the obd2 reader to measure AFR isn't the best idea but under throttle, the car begins to run lean around 20/1 which I know is really poor.
I think that is what is causing the sputtering and stalling at 4k rpms almost like it's hitting the rev limiter. I'm going to check fuel pressure tonight and crack open the tank to see if I have a clogged sock.
The car always sputters under full boost at 4k rpms but will rev out when I keep the throttle low. It occasionally will surge when taking off in first and second at low speeds. Maybe this is related to the other issue?
I know wrx fuel pumps rarely go out but is that something to consider? The fuel pressure test should help me diagnose that issue tho. I am thinking the issue is fuel-related currently. After replacing the MAF, spark plugs, and coils I'm not sure what else to check. The car is making its peak boost at 17 psi which is what the manual boost controller is set to so I don't think there are any leaks. Any other ideas would be very much appreciated. I'll do a leak-down test somewhere in the next couple of days and report my results. I'm still at a loss. Thanks for your help.
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