2003 WRX sputters ONLY WHEN WARMED UP
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This is a discussion on 2003 WRX sputters ONLY WHEN WARMED UP within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; I'm new to this forum but I figured I would ask for help since I have searched many hours online ...

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    2003 WRX sputters ONLY WHEN WARMED UP

    I'm new to this forum but I figured I would ask for help since I have searched many hours online but have found no solution.

    It only sputters out if 1. It's warm (exterior temp and engine temp) 2. Boost builds past 7psi.

    If the car is cold I can start it, let it warm up to operating temp, and it will build boost normal and pull hard. However after around 10 minutes of driving if I accelerate hard enough to build boost it will sputter. It seems to be around the 7psi mark (gauge reads .05 bar)

    I can also park the car and let it sit for 5 minutes or so, and it's like it hits some magic reset switch and it will drive and build boost as it should...but same thing happens after 10 minutes of driving.

    Only mods at the moment are:
    - SPT intake
    - Invidia down pipe
    - Invidia exhaust
    - Mishimoto intercooler hoses
    - Perrin manual boost controller

    Car is currently tuned for 16psi

    Other info:
    Fresh oil change
    Car has 60,000 miles
    Did a boost leak test and there appears to be none
    Cleaned MAF (car had a k&n filter on when I bought it so maybe MAF was damaged from filter oil?)
    No CEL light

    I am going to change spark plugs next.

    Anyone else ever had a similar issue or know what might be causing it?

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    New spark plugs..

    Changing coil packs tomorrow.

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    What engine management are you running for those mods?
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    Nothing at the moment. All I know is It was tuned using ecuflash. (I'm not 100% sure on the quality of the tune)

    I ordered a cobb accessport v3 which I understand can overwrite the ecuflash?

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    OMG WTF MainFrame's Avatar
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    It can, but you should be aware that the Access Port does not come with a map that will work with those mods. You will have to get a custom tune to be able to drive it safely.

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    Cobb only supports the stock boost controller and only the Cobb or aem intakes. The map notes will tell you what mods are compatible. The exhaust components are fine

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    Pro Manscaper Mikie13's Avatar
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    Quote Originally Posted by tezkr View Post
    Nothing at the moment. All I know is It was tuned using ecuflash. (I'm not 100% sure on the quality of the tune)

    I ordered a cobb accessport v3 which I understand can overwrite the ecuflash?
    Anything can overwrite anything...but an off the shelf Cobb map won't work for an MBC.

    An SPT intake won't cause problems with an AP. They don't do much on the 02 WRXs.
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    So if I get an oem boost controller I can run an ots map? Stage 1 I'm guessing?

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    Pro Manscaper Mikie13's Avatar
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    Quote Originally Posted by tezkr View Post
    So if I get an oem boost controller I can run an ots map? Stage 1 I'm guessing?
    Yes, if you put your boost control back to stock spec, yes you could run an OTS map. However you'd have to run a Stage 2 map with because you have a downpipe.

    Are you positive those are the only power mods you have?
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    Ok ya I found their map notes now. I'll just plan on trying the stage 2 map and see if it's an issue with the tune.

    Yes I'm sure. I'll try to get to the dealership before they close and have them order me an oem boost controller.

    Thanks for the help btw..first subaru so I'm still learning

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    Ok so put cobb stage 2 on, ran even worse. In the meantime I had ordered a new MAF sensor so I replaced it and that made a world of difference! I'm guessing the kid I bought it from had it tuned while the MAF was bad.

    Ok fast forward to today and I had a CEL. Looked it up on AP and it's reading p0037 (rear o2 sensor if my research is correct?) This had me curious so I started tracing wires and it turns out the rear o2 sensor is where the af gauge is reading from. Is this sensor necessary for the ecu to get proper data?

    The car runs strong but still feels like there may be a sensor or something somewhere causing it to loose a bit of power. Any input is appreciated!

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    The stock rear o2 sensor is only a cat efficiency sensor...at least on your year model I know it is. It's not a narrowband sensor like the front, which sends info to the ECU for fueling.

    What AFR gauge are you referring to? ..not sure I understand what you're saying. If you have an aftermarket AEM or LC-1 wideband gauge, they could have very well installed the wideband sensor in the rear o2 position and removed the cat efficiency sensor.

    The CEL code your receiving is heater core low, which means the sensor is burnt out or the wires are shorting out. But I was under the impression that the Cobb stage 2 tune would have defeated this error code.

    Interesting problem you got going on. I had a P0037 briefly on my Cobb stage 2 OTS tune, but I reset the code and it never came back. I think the lean AFR's I was experiencing may have secondarily triggered it. I've since fixed the AFR's and haven't had a P0037 since.
    Last edited by wreckingball man; 10-12-2013 at 06:34 PM.

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    Quote Originally Posted by wreckingball man View Post
    The stock rear o2 sensor is only a cat efficiency sensor...at least on your year model I know it is. It's not a narrowband sensor like the front, which sends info to the ECU for fueling.

    What AFR gauge are you referring to? ..not sure I understand what you're saying. If you have an aftermarket AEM or LC-1 wideband gauge, they could have very well installed the wideband sensor in the rear o2 position and removed the cat efficiency sensor.

    The CEL code your receiving is heater core low, which means the sensor is burnt out or the wires are shorting out. But I was under the impression that the Cobb stage 2 tune would have defeated this error code.

    Interesting problem you got going on. I had a P0037 briefly on my Cobb stage 2 OTS tune, but I reset the code and it never came back. I think the lean AFR's I was experiencing may have secondarily triggered it. I've since fixed the AFR's and haven't had a P0037 since.
    Its an aem wideband gauge. The wideband sensor is in the cat efficiency sensor spot. Ill look a little more in depth for shorts when I get home. I reset the code and drove it for a bit and it didnt pop back up so maybe I have the same issue.

    How did you fix your AFR's?

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    Mainframe was telling me about putting the wideband sensor in the rear o2 sensor bung, so maybe he could hep you sort that out. From what he was telling me it was a better location than what the AEM manual recommends. Like I said, I thought the AP was supposed to defeat that code, so I don;t know if you need a resistor in the circuit since the sensor is now missing or what.

    And how I fixed my AFR's, well, It's kinda complicated. I had a p0171, the P0037 only came up after the 171 was present for a while. I changed fuel filters then used injector and MAF cleaners. Then I changed the front o2 and the AFRs were correct again, but my fuel trim percentages are still kinda high. I'm still trying to get it worked out. My car never sputtered or hesitated, just ran rich (the computer thought it was lean, so it added too much fuel, making it rich).

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    Quote Originally Posted by wreckingball man View Post
    Mainframe was telling me about putting the wideband sensor in the rear o2 sensor bung, so maybe he could hep you sort that out. From what he was telling me it was a better location than what the AEM manual recommends. Like I said, I thought the AP was supposed to defeat that code, so I don;t know if you need a resistor in the circuit since the sensor is now missing or what.

    And how I fixed my AFR's, well, It's kinda complicated. I had a p0171, the P0037 only came up after the 171 was present for a while. I changed fuel filters then used injector and MAF cleaners. Then I changed the front o2 and the AFRs were correct again, but my fuel trim percentages are still kinda high. I'm still trying to get it worked out. My car never sputtered or hesitated, just ran rich (the computer thought it was lean, so it added too much fuel, making it rich).
    That's where the gauge is hooked up..it's linear with the AP's afr reading but the AEM gauge reads about .2 more so for my purposes at the moment it's accurate enough.

    Once the car warms up it will still loose power. I'm heading to the stealership tomorrow to order a new OEM front o2 sensor and a few vacuum lines.

    Good luck with your car..glanced over your build thread its lookin good. Clean paint man! Wish I had that paint

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