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Old 09-28-2015, 06:30 PM   #1
Scooby Newbie
Member#: 395447
Join Date: Jul 2014
Chapter/Region: E. Canada
Location: Sudbury, Ontario
2002 WRX

Default ej251 acceleration issues.

I recently bought a 2003 Impreza 2.5TS and everything is fine but the car WILL not accelerate properly. It drives perfectly fine, but as soon as I put my foot down the car bogs down and stutters. It accelerates and stops and accelerates and stops over and over until I let off the throttle again.

Could the fact the alternator is dead cause this? I'm replacing it shortly, the o2 sensors are replaced because they were throwing codes. Could is be a TPS sensor or MAP sensor?

Previous owner thought it was a head gasket but it doesn't leak coolant and the compression is a perfect 185psi across the board. I got a fantastic deal on it and would want it running.

I've replaced the plugs and have a brand new fuel pump if that could be the problem.

Car drives fine until pedal to the floor or even moderate acceleration then it starts to stutter and go from acceleration and letting off back and fourth.

Any help would be awesome, thanks!
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Old 09-29-2015, 02:02 AM   #2
Scooby Newbie
Member#: 3409
Join Date: Jan 2001
Chapter/Region: NWIC
Location: Oly
98 My FMIC
Is bigger than yours.


Were you getting a p0420 code? Sounds like maybe the cat is plugging up.
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Old 09-29-2015, 10:33 AM   #3
Scooby Specialist
Member#: 428511
Join Date: Aug 2015
Location: philadelphia
2016 STI


bad alternator couldn't cause that, if the alternator is toasted the battery supplies the power, so if you can start it then your battery is fine.

I would think a MAF issue could definitely cause that.

When it is in it's 'accelerating' phase prior to dying down, does the acceleration feel normal and sound right?
rtv900 is offline   Reply With Quote
Old 09-30-2015, 01:29 AM   #4
Scooby Newbie
Member#: 385766
Join Date: Mar 2014
Chapter/Region: SWIC
Location: Prescott Valley, AZ
1995 Legacy


The time I had a plugged cat long ago on a different platform it was a steady bog rather than cutting in and out. Seems like that is how it would always be unless there was debris in there that was pushed by exhaust flow to block the cat so it bogs and exhaust flow dies away so it drops clear, etc, etc.

Does it feel like an electonic kind of cut in and out or a physical thing? My current problem definitely feels electronic the way it cuts in and out.
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Old 09-30-2015, 03:50 PM   #5
Scooby Newbie
Member#: 431227
Join Date: Sep 2015

I just went through the same issue on my 02 RS. Replaced plugs, wires, both o2 sensors, and cat. Turned out to be my fuel pump.
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Old 10-07-2015, 12:25 PM   #6
Scooby Newbie
Member#: 378119
Join Date: Jan 2014
Chapter/Region: E. Canada
Location: Ottawa
2004 Impreza WRX
World Rally Blue


Fix that alternator.
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Old 10-13-2015, 12:59 AM   #7
Scooby Specialist
Member#: 318411
Join Date: Apr 2012
Chapter/Region: South East
Location: North Carolina
17 WRX


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