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Thread: Bad misfire - need some help here

  1. #1
    Join Date
    Jul 2012
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    Yardley, PA
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    98 M3/2/5

    Bad misfire - need some help here

    Update 8/19 - problem has returned after new coil.

    Hey all,

    The other night I decided to pull my seats and pull up the carpet to dry out after some rain got into my driver-side footwell. This is what I did in order:

    - disconnected the battery
    - pulled seats
    - pulled up carpet to air out
    - Couldn't get the driver's footwell carpet area all the way up without pulling the throttle out
    - Pulled throttle and put back in few hours later
    - reconnected battery but did NOT put the top bracket on top of the battery to keep it in place (was only going for a test drive)

    Went out for a 10-20 min drive and did a WOT in third - everything felt great. A few minutes later at a stop light it started misfiring consistently through all RPMs out of nowhere. Pulled over and noticed the negative end on the battery connection was spotty (probably because I never fully seated the battery with the bracket and it could've been moving around slightly while driving). I'd try starting it and the car went black as soon as I tried to turn her over. Went back and reconnected the battery tightly and it started up but still had the misfire. The car spit codes for P1637 and a misfire on cylinder 5. I have not pulled the valve cover to inspect for loose rocker arm shims but plan on doing that tonight after I'm back from work. I've tried cleaned the sensors on the pedal and the front TPS to no avail. Also tried reconnecting the battery, etc. Every time I start it it starts with the misfire and does not change through any RPM (nor am I limited to any RPM).

    Could the spotty battery connection have fried something like the throttle actuator? Idk...

    I am stumped.

    TIA,
    Hank
    Last edited by hkovalcik; 08-19-2018 at 12:33 PM.
    01/98 Porsche 996.1 911 - 2/6 - Current
    '03.5 M3 2/6 - Arizona bought - Wrecked 09/2018
    '06 WRX fully built/6 - Sold
    '95 323is/5 - Sold
    '95 325i/5 - Sold
    '01 540i/6 - Sold
    '03.5 M3 2/6 - Sold
    '02 M3 vert/6 - Sold
    '98 Cosmos M3/2/5 - Stg 2 AA Supercharged - Sold
    '98 M3/2/5 - Sold

  2. #2
    Join Date
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    Clear the codes,complete a short drive cycle,
    then perform a new scan for codes to confirm.

  3. #3
    Join Date
    Jul 2012
    Location
    Yardley, PA
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    98 M3/2/5
    Quote Originally Posted by MIKYZZ4 View Post
    Clear the codes,complete a short drive cycle,
    then perform a new scan for codes to confirm.
    Already did that. Same codes. Misfire cylinder 5 and 1637. I have a feeling the misfire is causing 1637 so i picked up an ignition coil from VAC here in philly - throwing it in tonight to see if it changes.
    01/98 Porsche 996.1 911 - 2/6 - Current
    '03.5 M3 2/6 - Arizona bought - Wrecked 09/2018
    '06 WRX fully built/6 - Sold
    '95 323is/5 - Sold
    '95 325i/5 - Sold
    '01 540i/6 - Sold
    '03.5 M3 2/6 - Sold
    '02 M3 vert/6 - Sold
    '98 Cosmos M3/2/5 - Stg 2 AA Supercharged - Sold
    '98 M3/2/5 - Sold

  4. #4
    Join Date
    Jul 2012
    Location
    Yardley, PA
    Posts
    822
    My Cars
    98 M3/2/5
    Quote Originally Posted by hkovalcik View Post
    Already did that. Same codes. Misfire cylinder 5 and 1637. I have a feeling the misfire is causing 1637 so i picked up an ignition coil from VAC here in philly - throwing it in tonight to see if it changes.
    ​FIXED. ^^ Ignition coil #5 was the problem. Cheers.
    01/98 Porsche 996.1 911 - 2/6 - Current
    '03.5 M3 2/6 - Arizona bought - Wrecked 09/2018
    '06 WRX fully built/6 - Sold
    '95 323is/5 - Sold
    '95 325i/5 - Sold
    '01 540i/6 - Sold
    '03.5 M3 2/6 - Sold
    '02 M3 vert/6 - Sold
    '98 Cosmos M3/2/5 - Stg 2 AA Supercharged - Sold
    '98 M3/2/5 - Sold

  5. #5
    Join Date
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    Great, I enjoy when a simple scan leads directly to a simple repair or replacement.

  6. #6
    Join Date
    Jul 2012
    Location
    Yardley, PA
    Posts
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    My Cars
    98 M3/2/5
    Update - problem is back. Started misfiring again this morning (have driven roughly 100 miles since installing the new coil). I'm wondering if the rain has something to do with it. A good bit of it gets in my trunk because the taillight gaskets are shot. I had duct tape over the edges under the trunk to prevent water getting in but have since taken the tape off with the intention of doing it right and getting new gaskets. I've read horror stories about a misfire on cylinder 5 being a re-occurrence and the only solution seems to be a new DME.
    01/98 Porsche 996.1 911 - 2/6 - Current
    '03.5 M3 2/6 - Arizona bought - Wrecked 09/2018
    '06 WRX fully built/6 - Sold
    '95 323is/5 - Sold
    '95 325i/5 - Sold
    '01 540i/6 - Sold
    '03.5 M3 2/6 - Sold
    '02 M3 vert/6 - Sold
    '98 Cosmos M3/2/5 - Stg 2 AA Supercharged - Sold
    '98 M3/2/5 - Sold

  7. #7
    Join Date
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    Chicagoland area
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    Perform a compression test.

  8. #8
    Join Date
    Jul 2012
    Location
    Yardley, PA
    Posts
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    98 M3/2/5
    Quote Originally Posted by MIKYZZ4 View Post
    Perform a compression test.
    You think there's damage?
    01/98 Porsche 996.1 911 - 2/6 - Current
    '03.5 M3 2/6 - Arizona bought - Wrecked 09/2018
    '06 WRX fully built/6 - Sold
    '95 323is/5 - Sold
    '95 325i/5 - Sold
    '01 540i/6 - Sold
    '03.5 M3 2/6 - Sold
    '02 M3 vert/6 - Sold
    '98 Cosmos M3/2/5 - Stg 2 AA Supercharged - Sold
    '98 M3/2/5 - Sold

  9. #9
    Join Date
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    Chicagoland area
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    EXOTICS
    Well we're trying to confirm a fault that's specific to cyl#5.

  10. #10
    Join Date
    Jul 2012
    Location
    Yardley, PA
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    98 M3/2/5
    Quote Originally Posted by MIKYZZ4 View Post
    Well we're trying to confirm a fault that's specific to cyl#5.
    I'll do a comp test but I don't think that'll give us much because I think she's healthy. I'm reading about the harness going bad and I'm wondering if that spotty battery from the first time I drove it wacked something like that. Regardless, at this point I'm going to replace all coils/plugs and do a comp test then. I'll report back with some results.
    01/98 Porsche 996.1 911 - 2/6 - Current
    '03.5 M3 2/6 - Arizona bought - Wrecked 09/2018
    '06 WRX fully built/6 - Sold
    '95 323is/5 - Sold
    '95 325i/5 - Sold
    '01 540i/6 - Sold
    '03.5 M3 2/6 - Sold
    '02 M3 vert/6 - Sold
    '98 Cosmos M3/2/5 - Stg 2 AA Supercharged - Sold
    '98 M3/2/5 - Sold

  11. #11
    Join Date
    Jul 2012
    Location
    Yardley, PA
    Posts
    822
    My Cars
    98 M3/2/5
    Replaced coil on cylinder 3. Everything is good, thanks. Misfire on cyl 5 was a misread since I had it unplugged
    01/98 Porsche 996.1 911 - 2/6 - Current
    '03.5 M3 2/6 - Arizona bought - Wrecked 09/2018
    '06 WRX fully built/6 - Sold
    '95 323is/5 - Sold
    '95 325i/5 - Sold
    '01 540i/6 - Sold
    '03.5 M3 2/6 - Sold
    '02 M3 vert/6 - Sold
    '98 Cosmos M3/2/5 - Stg 2 AA Supercharged - Sold
    '98 M3/2/5 - Sold

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