Need help troubleshooting engine - no code
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This is a discussion on Need help troubleshooting engine - no code within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Here's the situation: 06 WRX wagon - stock. 97k miles. Runs like a dream, always has. It's a smidge less ...

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    Need help troubleshooting engine - no code

    Here's the situation:

    06 WRX wagon - stock. 97k miles. Runs like a dream, always has. It's a smidge less boosty than at 4,00 miles, but I ain't complaining. I almost never drive below 9,000 ft elevation and on recommendation from Silverthorne Motors (Vista) service manager, I start using mid-grade gas instead of premium. Whenever I go to Denver, I throw in the good stuff. I don't have knocking issues. I frequently run at lowest possible RPM to save on gas. I've been doing this for 50k miles with no issues. I live 5 miles up a mountain and probably have ~8k miles on bumpy dirt roads to get to my house. Vibration and dirt are big issues. (once had a plug work out on my pickup)

    I do this myself, with a mechanic buddy helping me:

    I replaced the spark plugs for the first time. NGK plats, oem gaps. I know, too late, but the old plugs looked fine. White tips when pulled out.

    I replace the easy belts and check the timing belt and tensioner. All good. Better than expected. (hopefully not relevant, but I also did pads and rotors)

    I drive ~100 miles with no issues whatsoever.

    So, I'm driving up Trout Creek Pass in traffic, and RPMs drop, I pull over and it stalls out. I can get it started again, but it's really hard. The first few tries fail, but if I pump the throttle rapidly and I can get it started. On the first rev, I can get it to 6k RPM, but once it settles down, I can't get it past 4k RPM. Unless I flutter the gas pedal, it wants to stall. Eventually there is nothing I can do but either let it stall or turn it off. I get towed back home. This behavior hasn't changed, except maybe it's been getting harder and harder to get it started. It's not drivable. If I put it in gear, I have so little power, that I can't get up my driveway (kinda steep) and it wants to stall. It doesn't sound like a cylinder is missing, and I don't smell gas while someone else is keeping it running.

    No check engine light. I talk to the dealer, auto parts guys, mechanic friend, and a general Subaru mechanic that I trust. Respectively they suggest; fuel pump, knock sensor, MAF sensor, and IAC motor.

    The two little wires in the MAF look perfect. I can't really warm it up, but the car doesn't act any different with the MAF disconnected. Of course, it throws a code when I disconnect the MAF, but it goes away after I disconnect the battery.

    I took apart the IAC. It was a little grimy, I cleaned it, no change after I reinstall it.

    My neighbor suggests that I disconnect the fuel line somewhere, start it, and if it pushes gas out several feet, that's probably not it. I haven't tried it yet. I'm not sure where I would disconnect it.

    PLEASE HELP!! I can't afford to just buy parts as a simple troubleshooting step. Can I assume that there is a 0% chance of a sensor or IAC failure since there is no code? Does that leave me with only the fuel pump / filter assembly? Would any of you risk the $200 and replace the fuel pump/filter?

    Thanks in advance for your help.

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    Registered User devik's Avatar
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    Not sure if this helps at all, but I had the exact same symptoms about three years ago, turned out to be a shot injector. I'm pretty sure I threw a misfire CEL though.

    I'd say it sounds like a fuel system issue as well, but some others with more mechanical experience than me may be more helpful and can give actual troubleshooting steps.
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    Quote Originally Posted by devik View Post
    Not sure if this helps at all, but I had the exact same symptoms about three years ago, turned out to be a shot injector. I'm pretty sure I threw a misfire CEL though.

    I'd say it sounds like a fuel system issue as well, but some others with more mechanical experience than me may be more helpful and can give actual troubleshooting steps.
    Thanks! If my problem was fuel pump or filter, I can see us having the same symptoms, I guess. Assuming checking the injectors is hard, I'd like to rule out everything else first. I'm still hoping for a low-cost troubleshoot.

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    Registered User oguitar's Avatar
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    How old is the fuel filter? Has it ever been replaced?
    Life is like riding a bicycle in order to keep your balance you must keep moving.

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    Quote Originally Posted by oguitar View Post
    How old is the fuel filter? Has it ever been replaced?
    97k. Never been replaced. I'm told the pump and filter are one part, and from a diagram I've seen, that makes sense.

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    Registered User oguitar's Avatar
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    Looks a little complicated. On older WRX's the fuel filter is in the engine bay. Simple job to replace. Looks like you will have a bit harder of a time.

    Take a look at this it might be of some help. http://www.iwsti.com/forums/how-inst...placement.html

    I would start with the fuel filter. Report back what happens.
    Life is like riding a bicycle in order to keep your balance you must keep moving.

  8. #7
    He simply abides. SD_GR's Avatar
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    Well, one way to have a car that doesn't run but also not have a CEL is to run the motor out of fuel. I suppose the fuel filter is worth checking from what the OP said.

    I'd go back to premium fuel anyway unless there is a way to log ignition events.
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    Registered User EvoEatr's Avatar
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    FWIW, I've done many of the in tank fuel filters, Its prob about a half hour job even for a novice, The hardest part is pulling all the stuff out of trunk/back seat to get to the access cover...haha, however make sure the dealer has the filter before you disassemble everything, I know the dealer I am at (I believe) doesn't stock them...

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