Engine problems - dying MAF?
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This is a discussion on Engine problems - dying MAF? within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Hello all, Yesterday while driving in some heavy rain, my 02 WRX started to have some stumbling issues. When I'm ...

  1. #1
    Registered User devik's Avatar
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    Engine problems - dying MAF?

    Hello all,

    Yesterday while driving in some heavy rain, my 02 WRX started to have some stumbling issues. When I'm not in gear I can rev the engine up to 7k without problem (usually), but when I'm driving and I start to get on the throttle, the engine will respond until about 5100 rpm at which point it seems like the ECU is cutting fuel delivery, exhibiting that "fluttering" type of rev. Sometimes it's a higher RPM when it starts to cut out, sometimes lower, and it was idling pretty rough.

    I got a P0103 "MAF Voltage High" code thrown, so the amateur mechanic in me supports the 'dying MAF' theory, but a friend suggested that the MAF might have been throwing a fit due to the significant amount of water in the air during the rainstorm, and that -might- be what caused the CEL. I cleared the code, and that seems to have taken care of the rough idle; I've driven about one mile since clearing the code (I don't want to risk damaging my engine) and the code hasn't come back on. I'm not sure how long it would take for the ECU to report a problem again.

    What are your thoughts, folks? Any suggestions? Money is tight right now so I really can't afford to just drop a new MAF in, especially if it doesn't solve the problem, so I'd like a few options. I already plan to pick up some MAF cleaner with my next paycheck and see what that gets me, but does anyone else have advice?
    2002 Silver Bugeye WRX - Bugeye Mafia #327
    "Stage 2" + STI TMIC

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    He simply abides. SD_GR's Avatar
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    Engine problems - dying MAF?

    Is your intake faulty somehow? Rain should not be an issue. Check that the housing is closed and the lower tabs are seated and make sure the filter and MAF are clean and dry.
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    Registered User devik's Avatar
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    Quote Originally Posted by SD_GR View Post
    Is your intake faulty somehow? Rain should not be an issue. Check that the housing is closed and the lower tabs are seated and make sure the filter and MAF are clean and dry.
    I pulled the intake piping "upstream" of the airbox about two years ago, so the airbox is drawing from the wheel well, didn't consider water intake to be a problem since we very rarely get heavy rain here in AZ. I've never had a problem with it before this, but now I'm thinking it might've been a mistake :P

    The filter was a bit wet when I checked it, took it out to dry beore putting it back in, though I think it's probably still a bit damp deeper inside of the filter element, and I'm going to replace it before trying anything else.

    The airbox itself is sealed up, though a shop broke one of the lower tabs a few years back, so it's held in place by one of the plastic tabs on the engine-facing side of the airbox, and the two metal clips. I've checked the box every time I reassemble it and it always seems to be keeping a tight seal despite the missing tab.
    2002 Silver Bugeye WRX - Bugeye Mafia #327
    "Stage 2" + STI TMIC

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    Moderator Donkey's Avatar
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    Engine problems - dying MAF?

    If your filter was wet then you MAF is wet. MAF cleaner is like $5. If you are in a real pinch you can use non-chlorinated brake clean. Make sure you actually clean the MAF and not just the IAT sensor.
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