Misfire caused by exhaust leak ???

Discussion in 'Modifications And Maintenance' started by Paul Revere, Jun 6, 2009.

  1. Paul Revere
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    Paul Revere BANNED

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    So cliff notes for those who don't know first ... buy car mod car run car out of oil Subaru replaces block at 58k drive car blow motor at 90k (spun a bearing 3 and 4. Block was salvageable as it was driven no more than 6 miles after initial noise. Now has blueprinted crank and rods, ACL main and rod bearings, and stock pistons and rings.) fix that get car back and have 1700 on the block.

    Mods-

    New short block at 58100 miles ... rebuilt at 90k
    ACL main and rod bearings
    Blueprinted crank and rods
    Crucial Racing up pipe
    Invidia V3 divorced down pipe
    Billy Boat catback
    GMBCS
    Stock injectors
    Walbro 255 fuel pump
    K&N drop in filter
    Gimmick turbo inlet
    Perrin Y pipe kit
    Open ECU tunez

    PROBLEM!- So today is the first day since I got my car back that it has rained heavily here. Car drove flawless no hiccups, stutters, no cels until today. Now it seems like I have a pre turbo exhaust leak at on the passenger side (i say that because thats where the popping/backfire is loudest) and I have a rough idle and cylinder 4 misfire and cel that flashes/stays solid/flashes/stays solid/flashes ... Under load the car builds boost then as soon as the wastegate opens it like acts weird for a little while then drives normal and so on and so on. Also my car seems to pop a lot more than before the motor rebuild ... like all the time.

    Question- Could that exhaust leak cause a rough idle and misfire if the ambient air is coming in contact with the front 02 sensor?

    Its raining and I have no way to currently put it in some kind of shelter so I will let it sit and think about how bad it is for the time being. Like a time out. Maybe drive it tomorrow when its not so wet or I can crawl on the ground and tighten the exhaust.
     
  2. Shibbs
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    Shibbs The Daywalker

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    First off, if its not running right, DON'T BUILD BOOST, DUMMY. haha

    Second, any leaks could definitely cause a CEL.

    Are you running a blowoff valve? That set too loose could be your popping issue.
     
  3. readymix
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    readymix ...Lest ye be trod upon... Staff Member

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    If it is the popping I am assuming it is, it's probably coming as he applies throttle from idle or between shifts at low rpms. Kindof a "THUNK" noise from the drivers side, from in the car it probably sounds like it is blasting out the side of a loose exhaust manifold, am I right?

    If i were you, I'd go grab some 14mm sockets and get under there and start tightening up your joints all the way from the manifold back to the midpipe. An exhaust leak can cause serious pressure and turbulence issues especially pre-turbo. Your car's ability to move gas from the exhaust ports on your heads to the back of the car is crucial to it running properly.
     
  4. Paul Revere
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    Paul Revere BANNED

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    Jason picked up what I was putting down, yes that is basically what is happening. I plan to work on it tomorrow if I can ...
     
  5. Paul Revere
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    Paul Revere BANNED

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    Just drove it again to make sure ... this is really bugging me!!! I guess it could be a coil pack or anything I guess ...
     
  6. readymix
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    readymix ...Lest ye be trod upon... Staff Member

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    The only reason i can tell you in detail what you are experiencing is because my car does it, and did it before. I tightened up all the bolts on the exhaust and it seemed to go away for about a year. Also, check the hangers for your exhaust and make sure they are all connected and tight, that keeps your exhaust from waggling about under load and loosening up the bolts.
     
  7. Paul Revere
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    Paul Revere BANNED

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    Well you can lock this and keep it open for others or just keep it open but Mike Wray found the problem, it was a loose connector on cylinder 4's coil pack.
     
  8. WRX1
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    WRX1 _ Staff Member

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    Well, I can tell you this, ANY exhaust leak will not suck in air, the exhaust will come out, but it will not suck up fresh air.

    A pre-turbo (uppipe leak), kinda sounds like a pissed off squirrel.

    And since you have a flashing cell (which means you should not be driving it or getting into boost), what is the code??

    Russ
     
  9. Paul Revere
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    Paul Revere BANNED

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    It was a mass air flow sensor code (because I was instructed to disconnect the sensor), cylinder 1, cylinder 2, cylinder 4, and a temp code. We didn't know what it was but now all is fine, ran a little rough at first after fixing it ... cylinder 4's plug was pretty fouled out I'm guessing.
     
  10. AWDimprezaL
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    AWDimprezaL has more posts than you

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    #1 quit beating on it, even if its running good...
    #2 get rid of it before it burys you in debt.
     
  11. Shibbs
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    Shibbs The Daywalker

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    Too late for #2.
     
  12. Paul Revere
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    Paul Revere BANNED

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    Gotta pay to play ... I just seem to have bad luck with this car, sadly I think the last motor went because of an over looked part :(