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  1. #1
    Active Member Two Rings cdc's Avatar
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    Jan 04 2008
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    23854
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    Menifee, CA

    Back in an Audi but missfire problems when warm P0305 05 Allroad

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    Finally picked up an Audi again after owning a B5 S4 a few years ago, this time its an 05 Allroad 2.7t. I have encountered my first problems that being P0305 miss fire but only when the car is warm when cold it runs perfect.

    I have tried switching coils, plugs and done a compression test (120+ psi on all cylinders) and I am in the process of replacing the ignition coil connectors.

    Does anyone have any suggestions of what I can try next? On cold start everything is fine but you can feel the car starting to miss fire the warmer it gets then it triggers the CEL.

  2. #2
    Veteran Member Four Rings
    Join Date
    May 09 2012
    AZ Member #
    93306
    My Garage
    08 A4 Avant, 05 Silver S4 2.7t swap
    Location
    Virginia

    Are the misfires following the coils or not? Canít blame ICMís. The 120 psi is on the lower end of spec I believe. What do the spark plugs look like?


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  3. #3
    Veteran Member Three Rings m_haiser's Avatar
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    Apr 24 2011
    AZ Member #
    74529
    My Garage
    Highland Green Allroad
    Location
    Oregon Coast

    Check the coolant temp sensor too

  4. #4
    Active Member Two Rings cdc's Avatar
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    Jan 04 2008
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    23854
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    Menifee, CA

    Iíve moved the spark plugs and coils to different cylinders but the misfire stays with cylinder 5. Would the coolant temp sensor cause a misfire in only one cylinder?

    Also just to confirm cylinder 5 is the middle cylinder drivers side correct?

  5. #5
    Veteran Member Four Rings
    Join Date
    May 09 2012
    AZ Member #
    93306
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    08 A4 Avant, 05 Silver S4 2.7t swap
    Location
    Virginia

    Quote Originally Posted by cdc View Post
    Iíve moved the spark plugs and coils to different cylinders but the misfire stays with cylinder 5. Would the coolant temp sensor cause a misfire in only one cylinder?

    Also just to confirm cylinder 5 is the middle cylinder drivers side correct?
    Thatís correct regarding the cylinder order. If it isolates to cylinder 5 you probably need to do a leak down and/or pull the head assuming the spark plug looks ok. It may be worth just swapping the plug out first regardless and see what happens.


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  6. #6
    Active Member Two Rings cdc's Avatar
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    Jan 04 2008
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    Menifee, CA

    When I did the compression test I left the tester in the cylinder to see if it held pressure and it did. Today I moved the plugs around and even switched injector 5 for injector 1. It still misfires on cylinder 5.

    Iím totally lost as to whatís wrong with it.

  7. #7
    Senior Member Two Rings Calif_Kid's Avatar
    Join Date
    Oct 14 2006
    AZ Member #
    12545
    My Garage
    2001 A6 6 spd, 2000 Honda Civic hatch racecar
    Location
    Sunnyvale, Calif

    Did you swap the two ICMs (that are on top of the airbox) to see if the misfire switched to the other bank? If you havenít tried that, then give it a shot.

    I was going to mention maybe swapping the fuel injectors around, but then I saw that you just tried that, and it didn't help. I was thinking that it wouldn't hurt, that with the car at idle and the engine cold, to try moving the wires going to the coilpacks slightly, and see if you start hearing a miss (and/or getting a code). Just thinking that maybe the wiring going to cylinder number 5 is a little messed up, but only shows itself when the engine is warm. It is good, that the problem seems to be consistent.

    I did a quick search for P0305 in the B5 S4 as well as the C4/C5 A6/S6/RS6/allroad forums, and there are quite a few threads. Iím not sure if there is anything in the ECU that could cause the issue (that only shows up as the engine warms up), but it seems more likely that it is something else. For the engine coolant temp, even if there isnít any codes for it, you might take a look at its reading in Vagcom when the engine cold, plus as it starts to warmup, and see how stable and reasonable the reading is. - Jim

  8. #8
    Veteran Member Four Rings
    Join Date
    May 09 2012
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    08 A4 Avant, 05 Silver S4 2.7t swap
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    Virginia

    I still think a leak down to look at the rings may be in order.

    Shouldnít have to worry about ICMís. Itís a 2005.


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  9. #9
    Senior Member Two Rings Calif_Kid's Avatar
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    Oct 14 2006
    AZ Member #
    12545
    My Garage
    2001 A6 6 spd, 2000 Honda Civic hatch racecar
    Location
    Sunnyvale, Calif

    Quote Originally Posted by jbain2 View Post
    I still think a leak down to look at the rings may be in order.

    Shouldnít have to worry about ICMís. Itís a 2005.


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    Good point about the ICMs... I've done compression tests, but have never done a leakdown test. Are leakdown tests usually done with the engine cold or warm? Just wondering about if the rings are an issue, why they would only start causing the misfire after the engine warmed up, plus if the ring sealing was temp sensitive, if it would show up in the leakdown test. Thanks!! - Jim

  10. #10
    Veteran Member Four Rings
    Join Date
    May 09 2012
    AZ Member #
    93306
    My Garage
    08 A4 Avant, 05 Silver S4 2.7t swap
    Location
    Virginia

    Quote Originally Posted by Calif_Kid View Post
    Good point about the ICMs... I've done compression tests, but have never done a leakdown test. Are leakdown tests usually done with the engine cold or warm? Just wondering about if the rings are an issue, why they would only start causing the misfire after the engine warmed up, plus if the ring sealing was temp sensitive, if it would show up in the leakdown test. Thanks!! - Jim
    Leak down is a static test with the engine off and cold typically. Looks at rings and pistons. I would expect though for the compression numbers for cylinder 5 to be off honestly. So not entirely sure whatís going on.


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  11. #11
    Active Member Two Rings cdc's Avatar
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    Jan 04 2008
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    23854
    Location
    Menifee, CA

    Today I did a running compression test on cylinder 5 when the car was warmed up. Compression dropped to 60psi with the car running.

    Thanks for the help with the problems I really appreciate it.

  12. #12
    Veteran Member Four Rings
    Join Date
    May 09 2012
    AZ Member #
    93306
    My Garage
    08 A4 Avant, 05 Silver S4 2.7t swap
    Location
    Virginia

    Quote Originally Posted by cdc View Post
    Today I did a running compression test on cylinder 5 when the car was warmed up. Compression dropped to 60psi with the car running.

    Thanks for the help with the problems I really appreciate it.
    Pull the head off with cylinder 5 at TDC. Look at valves and seats. While you have the head off you can pour some oil in piston 5 and see how well it holds it. Hopefully its just the head which you can replace fairly inexpensively.

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