A4 1.8t rough idle

Discussion in 'General Vehicle Chat' started by Craigcorson, Mar 11, 2018.

  1. Craigcorson

    Craigcorson Forum Member

    Joined:
    Nov 1, 2013
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    Location:
    Inverkip
    Got a 2005 a4 cabrio, again....

    This one has a rough idle with the occasional yellow light.

    Had initially thought it was the PCV valve UFO thing next to the bulkhead.

    Replacing that has improved it slightly but after searching the internet most people say try and take the oil cap off when running.

    With the old valve I could, just. With the new one its much worse.

    Got a couple of spare coil packs which was a doh moment. Should I be looking for another valve or a vacuum leak?
     
  2. Savagesam

    Savagesam Moderator Staff Member Moderator

    Joined:
    Nov 24, 2012
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    1,096
    I'd go vacuum leak, mine was horrible at idle when I had one. I thought I'd broken something but it'd just got brittle with age and cracked.
     
  3. GVK

    GVK Paid Member Paid Member

    Joined:
    Oct 23, 2003
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    Location:
    Lincs.
    Disconnect the MAF see if idle improves could be dead MAF or vac leak as above.
     
  4. Craigcorson

    Craigcorson Forum Member

    Joined:
    Nov 1, 2013
    Likes Received:
    80
    Location:
    Inverkip
    problem solved, 3.20 check valve located underneath the inlet manifold

    woohooo
     

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