Audi 2.8L 30V Misfire at Idle

Discussion in 'Everything Technical' started by 88Quattro, May 4, 2017.

  1. 88Quattro

    88Quattro Well-Known Member

    I have a 99 A6 with the 2.8L 30V V6. The car runs well driving around but will misfire at idle. It's so bad that it will cause a flashing MIL. The issue is worst with light load (neutral). Misfire just about disappears in gear. Add in AC and it's totally gone. Misfire occurs on all cylinders and gets worse as it warms up.

    Things I've changed/checked:
    spark plugs
    cam timing
    smoke intake
    pressurize intake
    Throttle body adaptation
    O2 sensors (front)
    PCV is currently bypassed. No change
    fuel pressure regulator/verify pressure
    Compression test (220ish on all 6)
    fuel trims around 0

    I'm all ears on ideas.
  2. rabbit20v

    rabbit20v BRIDGE!

    Do you have the correct spark plugs? These engines were very picky about that.
  3. vw to bimmer

    vw to bimmer The Krazy Professor

    after the plugs, your crank position sensor can do some wacky things when it is going out.....
  4. 88Quattro

    88Quattro Well-Known Member

    I think I put the proper plugs in: NGK BKR6EKUB I'm more than happy to try something else that someone is 100% on.

    How can I check the crank sensor? Or is it just replace with new or known good?

    Thanks for the responses.
  5. rabbit20v

    rabbit20v BRIDGE!

    That's the correct spark plug.
  6. rabbit20v

    rabbit20v BRIDGE!

    How is the PCV system bypassed?
  7. 88Quattro

    88Quattro Well-Known Member

    PCV: I plugged the port pre throttle body and also on the vacuum side. Interestingly enough, the car seemed to run better when I reconnected it, even with the PCV blowing freely both ways. Not sure if I missed a connection to the PCV system. I have a new complete PCV valve and hose system to install when I get a chance. Since the valve didn't check I thought it was best to replace, even if it wasn't the cause.

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