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Thread: Case Study: 2009 Passat CC 2.0T CCTA, #2 and #3 misfires from hell

  1. #1
    Ross-Tech Employee Jef's Avatar
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    Jan 2014
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    Case Study: 2009 Passat CC 2.0T CCTA, #2 and #3 misfires from hell


    Repair shop had done an engine swap from a low mileage donor car. Engine runs great, but will flag #2 and #3 misfires (can't feel them) when the engine is between 2000 and 3000 RPMs, no other time.

    • Compression is about 185 across all 4 cylinders.
    • New coils and plugs installed, juggled around as well.
    • New injector installed.
    • Checked fuel trim values, great readings, no false air issues.
    • Intake and valves inspected, no carbon.

    I had him check fuel pressure, rail pressure is good, but the lift pump duty cycle started of at 52% and later went as high as 62%, so from not so good to not good. Find out that during engine swap, the Fuel Rail Pressure Sensor (G247) was not swapped over. Got the original G247 installed, this fixed the lift pump duty cycle issue, down to 47% now, but still misfires on #2 and #3 between 2000 and 3000 RPMs.

    With key on, engine off, went into the ECM and did 4 or 5 clear DTCs commands back to back as fast as he could. Exit out of ECM, cycled the ignition and started the engine, no more misfire codes when revved up.

    It would appear that in some cases, issuing several clear DTCs back to back in a very short time frame can do a deeper level reset of the ECM.

    I have to give Peter credit for trying that.
    Ross Tech Support Team, Alpha Squad
    Auto-Scan, learn it, love it, live it... then check the fuses.

  2. Likes Uwe, Dana, Bruce, jyoung8607 liked this post
  3. #2
    Verified VCDS User
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    Apr 2019
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    Just ran into the same problem. Did a motor swap in a 2011 Tiguan, new timing set, rear main, decarboned, resealed all injectors, and resealed oil pan. False misfires on cyl 2&3 at 3400+ rpm. Tried a cap discharge and that didn't do it. Finally fixed it once I came across this post, sent 6 clear codes commands in a row.

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