Question Engine R55 Clubman 100K+ Misfire at Idle Has me Stumped!

Discussion in 'General Technical Questions and Answers' started by Rob-GA, Jun 1, 2022.

  1. Rob-GA

    Rob-GA New Member

    Jun 1, 2022
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    #1 Rob-GA, Jun 1, 2022
    Last edited: Jun 2, 2022
    First time poster, so please go easy on me!

    I have a lot of experience wrenching on BMWs and have now learned more than I probably want to about MINIs (but clearly not enough). I've got one now that truly has me stumped and I'm looking for some advice.

    The subject is a 2009 Clubman with a 6MT and around 115K miles - base model with the N12. It came to me with a leaking thermostat housing, a fault code for the pre-cat O2 sensor, and the dreaded random multiple misfire. I replaced the t-stat and O2 sensor along with new coils/plug. That took care of the coolant leak and O2 sensor code, but the misfire is still there. It was very noticeable while I was running the engine to bleed the coolant and according to my scan tool, #3 is the worst offender. There are occasional misfires on #1 and sometimes #2, but #3 is by far the worst.

    What's weird is that the misfire goes away when driving. When I watch the data stream with the engine idling, it's very obvious that #3 is badly misfiring, with only occasional misfires from #1 and #2. But as soon as I start driving, all misfire monitors drop to 0 and stay there until I stop and allow the engine to idle - then they come right back.

    I suspected that I may have a lazy injector, so I swapped the entire set from another MINI that isn't having any drivability problems. It made to difference.

    Then I thought that maybe, somehow, I got a defective plug/coil. So I swapped those from the other car. It made no difference. While I was at it, I unplugged the coil for #3 with the engine running and it ran even worse. So that seems to suggest that the plug for #3 is getting power and sparking.

    Low fuel pressure due to a weak pump or clogged filter? I tested the fuel pressure and it's 54 psi.

    Low compression due to head gasket issue or burned valve?
    #1 = 175 psi
    #2 = 162 psi
    #3 = 162 psi
    #4 = 178 psi

    Maybe #2 and #3 are a bit low? But only 16 psi difference between the highest and lowest.

    I'm at my wit's end with this car and have run out of ideas. Is anyone seeing anything here that I missed, or interpreting the data in a different way that offers a clue about what's going on?

    Thanks in advance!
     
  2. MCS02

    MCS02 Moderator
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    If this is an S with the N14 motor it may need to have the intake valves walnut blasted. On the S with the turbo they are bad about building up carbon on the intake side. They can do it in as little as 35-40k.
    is it an S?
     
  3. MCS02

    MCS02 Moderator
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    Welcome to MA!
     
  4. 00Mini

    00Mini Well-Known Member

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    Nice catch on the intake valves. That’s why you get the big bucks. :rolleyes::D
     
  5. Metalman

    Metalman Well-Known Member
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    My guess it's a non-S because of the comment of 54 psi.....
    Non-S gets the valves cleaned with fuel contact, so shouldn't have carbon buildup issues ....
    OP should post the engine type or it's going to be a guessing game...

    The S has 2 fuel pumps..... LPFP in the tank, and a HPFP mounted on the head....
    LPFP runs at about 5 bar (73 psi)
    HPFP runs at about 50 bar (725 psi) at idle and 120 bar (1,740 psi) at WOT....

    Need more info....
     
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  6. Rob-GA

    Rob-GA New Member

    Jun 1, 2022
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    #6 Rob-GA, Jun 2, 2022
    Last edited: Jun 2, 2022
    Not an S. It's an N12 base model. I should have specified that! I edited the original post to include the engine type.
     
  7. 00Mini

    00Mini Well-Known Member

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    Welcome to Motoring Alliance
     

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