Misfire/Jerky Acceleration - Subaru WRX Forum
 
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#1 Old 01-11-2012, 05:21 PM
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Misfire/Jerky Acceleration

I purchased my 2007 WRX wagon a year ago and I have had a recurring issue with misfires or jerky acceleration. All that I have have not stock as of now is a spt intake and a muffler. Originally I was getting CEL code P2097 and Subaru (three different dealers) all told me they didn't know what the issue was and that my car was running fine which it clearly isn't (one dealer told me off the record he suspected a cat but wouldn't recommend an expensive repair on essentially a hunch). I replaced my O2 sensor, plugs, fixed a vacuum leak, and all new belts and my CEL was off for several months, but the car would still periodically misfire. Since then I have had code P0420 (inefficient cat) thrown a couple of times. The misfire occurs under load typically during any acceleration or going up hills and seems to happen through a whole tank of gas. I always put in premium and try to hit up name brand gas in up scale areas... As of now I am planning on going with a new catted downpipe and accessport, but I don't want to drop the cash if the problem is somewhere other than the cat. Any thoughts would be appreciated. I have also toyed with the issue potentially being an something with the fuel system (injector, pump, etc...)

p.s. Feel free to give me suggestions on how to better post or use the site if I newbed something up here as it is my first post....
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#2 Old 01-12-2012, 05:56 AM
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You posted in the right place. So you replaced the rear O2 sensor. How do you know it's misfiring without any misfire codes?

Have you done a compression check ?

Paul
2002 WRX Sold
2007 WRX Sold
2007 STi totaled
2007 Foz XT sold
2007 MS3
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#3 Old 01-12-2012, 08:00 AM
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If it's misfiring it should be throwing a code for which cylinder it's actully missing in.

Then, if you actually do have a misfire code, figure out which cyliner it is and move that coilpack around to see if the miss follows the coil.

Other than that, try cleaning out the MAF and the FRONT 02 sensor in the headers (if you already didn't, you didn't specify which one).

Pretty much that's from free to $5 for maf cleaner to $150 for the sensor.

-Chris
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#4 Old 01-13-2012, 04:05 PM
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It has never actually thrown a misfire code that is just what it feels like. I replaced the front o2 sensor and I have cleaned my MAF. I could understand how my cat would make it feel like it was missing if it was limiting flow, but didn't know if that would produce the same CEL code. I have not done a compression test and not sure if one was done when my plugs were replaced. If compression was the issue would it be a periodic problem or more consistent?
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#5 Old 01-14-2012, 09:25 AM
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You mention your modes include a SPT intake and a cat back exhaust. Is your car currently tuned? I know you said you wanted to by an AP in the future.

I ask because your car is very sensitive to any modification to your air intake system and should therefore be tuned to handle the larger volume of air or you'll most likely be running very lean. Not sure if this is the problem you've been experiencing. One thing you could do (if your car has not been tuned) is re-install the factory air box and see if it corrects your issue. If it does, then wait to install the intake until the car is ready to be tuned.

Hope this helps

2011 WRX Premium Sedan - WR Blue
Cobb AP Stage 1 93 & Cobb SF Intake
Short Shifter
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#6 Old 01-15-2012, 07:38 AM
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Check the fuel filter. I had a very similar issue with mine a few months ago. Filter fixed it right up. Its easy to change and not expensive at all. I paid 20 bucks for a wix at oreillys. The regular one was about 12 i think.

Kevin.
Cobb ap stage 2 ots, catless uppipe, catless turboback, Cobb Sf intake.
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#7 Old 01-15-2012, 11:18 AM
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I don't think that there is a replaceable fuel filter on the '07s I think it is essentially a screen at the pump.... I will be buying an AP and downpipe as soon as possible (probably won't be till I get my tax return) and hope that some EM and unrestricted flow will take care of it. I can't put the stock air box on since my car came with the spt on it. If nothing else it's a good excuse to go stage 2.
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#8 Old 01-15-2012, 12:10 PM
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Generally these cars are pretty good at picking up a misfire, so good that usually if one cylinder misfires, it'll throw that code as well as a multiple misfire code. Just saying I think the sensors would pick it up if it did.

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