1st Gen R50 Cooper R50 misfiring on cylinder #1

Discussion in '1st Generation: 2002–06 R50, R53 & 2004–08 R52' started by jeffster06, May 20, 2015.

  1. jeffster06

    jeffster06 Active Member

    Apr 23, 2010
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    So I don't have all the details yet but will have the car at my house this weekend to really dig in (helping a coworker). Here is what I do know after looking at it for about an hour in a dim lit parking garage.

    Cylinder #1 misfires at idle, my scanner counted about 120 misfires while idling in the garage. (approx 10 mins of idle time)

    It only seems to misfire while idling

    The car has been worked on and the shop is now suggesting pulling the head to take a look, this seems like overkill as there are not odd noises like a valve sticking etc. that and holding throttle smooths it out.

    For some reason cylinder 1 has auto tranny fluid in (enough to see the red in the tube but not flooded) and around the plug hole on the valve cover. To me this was extremely odd as the car is a 5 speed so I have no idea why its there. (first thought was accidental spill)

    From what I have been told is the coil pack has been replaced (it looked new), plug wires (they didn't look new but number one was sparking when I pulled it during idle), she said the shop tried new plugs and that didn't help the problem but couldn't say if they left the new ones in.

    My thoughts are when I get the car I will do a compression check, inspect the plugs and wires (I may try using a set of plug wires I have on my shelf).

    What are some other things I should be looking at? is it possible she has a slightly clogged injector?
     
  2. cristo

    cristo Well-Known Member

    Jan 4, 2015
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    I'm wondering if the red ATF was put into the cylinder to do a compression check at the shop (usually you
    check first without and then with some oil or similar added to see if that helps the numbers or not).
     
  3. jeffster06

    jeffster06 Active Member

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    I had that thought as well, but I've always used a few drops of oil. makes me wonder if the shop did a compression check and found cylinder one reading low.
     
  4. Eric@Helix

    Eric@Helix New Member
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    Yep, one would hope that it was put there deliberately, because if trans oil is finding it's way into the #1 plug journal, there's a whole heap of trouble.

    Start with a compression test (inspect the plugs as they come out). It's unlikely that it's your wires, but that's easily tested by swapping the number 1 wire with another one and see if the misfire follows the wire.

    Don't pull the head until you've confirmed that there's a compression issue.
     
  5. RallyMini370

    RallyMini370 Well-Known Member

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    I bet it's a burnt out exhaust valve. My R50 had the same issue on #2 anyway as Eric says do a compression check first.
     
  6. jeffster06

    jeffster06 Active Member

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    I have been searching for this issue and came across the burnt valve threads, I really hope its not that.
     
  7. aslondon

    aslondon Member
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    Please keep us posted. Inquiring minds want to know.

    Al
     
  8. ZippyNH

    ZippyNH Well-Known Member

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    Hate to say...a burnt valve is preferable to a piston/ring issue....sure the head comes off, but the engine stays in...
    A good compression check, wet and dry by a pro, will give you a good idea what's up...
    Good luck.
    Guess you could move the injectors...use new o-ring if you do too see if it follows the injector, but gut says valves....so many have gone over the years, some due to low octane fuel letting the valves run hot, some from just wear.
     
  9. ZippyNH

    ZippyNH Well-Known Member

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    P.S.
    Misfire at low rpm is typical of lower compression....
    As the rpms increase, there is less time for the air to leak out on the compression stroke...
    So symptoms match...if it is the valves it typically worsens rapidly....
     
  10. ColinGreene

    ColinGreene Well-Known Member
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    Leak down test would be better.
     
  11. RallyMini370

    RallyMini370 Well-Known Member

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    Well if it is a burn valve I have the original head in the garage as I fitted a MC head with better valves. if you need a valve I can send you some. Gratis!
     
  12. jeffster06

    jeffster06 Active Member

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    I have learned some more info on the car today, The shop that has been working on it did a compression test and cylinder 1 was half the tolerance it should be (didn't specify the number). Looks like the head will be coming off.

    Before I go pulling the head is there anything else I should check for?

    Also if I pull the head what are some other items I should tackle while in there, new timing chain? etc.... this MINI has approx 117K on it.

    Should mention the shop that has been working on the MINI seems to know what they are doing but my co worker is having sticker shock as the repairs are amounting to almost the purchase price of the car (oil pan gasket and passenger axle are bad as well). I just happen to be a nice guy and won't charge her what they were going to.
     
  13. RallyMini370

    RallyMini370 Well-Known Member

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    This is how I found out it was a burnt out valve: I took the valve cover off to see when both valves were closed on the suspect cylinder. I then connected an air line to the compression tester line. I blew air into the cylinder and then put my hand over the tail pipe. I could feel air coming out which confirmed the burnt out valve.
     
  14. jeffster06

    jeffster06 Active Member

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    Just got the MINI home, this poor thing needs some help, noticed the cooling fan running on high when I turned it off, quick check using the AC the low speed fan isn't turning on. I also noticed a weird metallic noisy while it's idling, thinking maybe an idler or belt tensioner. To think I haven't even got to really looking at it. Oh and the door handle on the driverside doesn't open from the inside.
     
  15. RallyMini370

    RallyMini370 Well-Known Member

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    Door handle is the cable from the inner door pull has popped out at the lock end, I glued mine in. quite easy to fix. The rest will need some work. Well it is the weekend and that's what weekends are for!
     
  16. jeffster06

    jeffster06 Active Member

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    Yea the handle issue will probably be the easiest to fix lol. Luckily they don't need the car back until mid July so I can take my sweet time, although the longer I look the more I'll find.
     
  17. jeffster06

    jeffster06 Active Member

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    #17 jeffster06, May 25, 2015
    Last edited: May 25, 2015
    Finished checking the compression *cold*
    #1: 50 psi
    #2: 90 psi
    #3: 90 psi
    #4: 80 psi

    *hot*
    #1: 91 psi
    #2: 200 psi
    #3: 200 psi
    #4: 150 psi

    #4 also appears to be low when warm, the cold numbers were only cranked for 6 cycles, warm I went to max. #4 was taking longer to achieve so I stopped it early.
     
  18. jeffster06

    jeffster06 Active Member

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    Got the head off this morning, this job was almost too easy. Maybe I just anticipated it being harder, took me 4 hours to get it off, this was with taking breaks and removing the radiator (needs a cooling fan fix) which wouldn't have been neccesary.

    Cylinder one has a burnt exhaust valve. So next up is to get the head fixed/refreshed and reassemble. I still have quite a bit left to fix but I'm happy to get this part partially knocked out
     

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  19. RallyMini370

    RallyMini370 Well-Known Member

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    just like mine, buggered. I'd go get a used R53 and drop that on. I found a 20,000 R53 head on Ebay for $90
     
  20. RallyMini370

    RallyMini370 Well-Known Member

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    #20 RallyMini370, May 31, 2015
    Last edited: May 31, 2015

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