Running rough and no codes

Discussion in '2nd Generation: 2007+ R55 through R61' started by Neil, Jul 25, 2018.

  1. Neil

    Neil New Member

    Jul 25, 2018
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    Working on 2008 MCS N14. Engine blew exhaust valve without warning. Had cylinder head repaired at local performance machine shop. After reassembling engine it continues to run rough. Compression test before initial start up was low but still in range. 130,138, 116, 135. Bentley says 8-12 bar +- 3bar variance. 3 was the bad cyl and with it being the lowest it is concerning. Granted it had zero compression before cyl head repair but still concerning. Would’ve liked to see higher and more consistent numbers with refurbished head but nothing I can do about it now. I just need it to run. I don’t have any misfires or any trouble codes. No MIL. Timing is good. I’ve got new o2 sensors. Plugs replaced Les than 20k ago but I did have to replace #3 because it melted when the ex valve did. Fuel rail pressure at idle about 700psi. I just don’t know what to do. Any suggestions are greatly appreciated.
     
  2. MCS02

    MCS02 Moderator
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    Did they check the head for cracks? If it is not the head it may be a bad piston or rings. You could put some oil in that cylinder and see if the compression comes up. if it does your rings are bad.
     
  3. Dave.0

    Dave.0 Helix & RMW Powered
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    You posted the same thing on the NAM. I think your problem is Thumpers crap head and CAM.

    Do you have a tune on your car? Take it off and set it to stock tune. Test.

    If you have your old Head and CAM put them back in and test again.


    Thumpers parts and heads are known to be crap but people still buy them and us old heads have no idea why.
     
  4. Neil

    Neil New Member

    Jul 25, 2018
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    Yes they checked the head. Wet compression test had no change in numbers. Thanks for the post.
     
  5. Neil

    Neil New Member

    Jul 25, 2018
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    #5 Neil, Jul 25, 2018
    Last edited: Jul 25, 2018
    I did post on NAM but I think you might be confusing me with another post. My car is all stock. I haven’t purchased anything from thumper. I’m just trying to reach more folks for input so I joined MA. Everyone on NAM has been super cool and I appreciate all the replies. I’m just kinda stuck and looking for advice.
    Would you know why from a cold start the motor runs in closed loop and closed loop fault? What do you think about those compression numbers? 130,138,116,135 Is Bentley wrong with the 8-12bar? It starts up right away no problem but runs horribly. Even with 680psi atvrail could I have a hpfp issue? I just don’t know what’s going on.
     
  6. MCS02

    MCS02 Moderator
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    things that come to mind then are, Bad head gasket, the head needs planing, a valve is not seated or lapped in properly,Vanle not adjusted correctly, Head has a crack that was not pound. If you feel sure the bottom end is good you have a problem with the head. How does the cam look?
     
  7. Neil

    Neil New Member

    Jul 25, 2018
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    Cam looks like hell but it should run. Never seen cams wear like this. I had an old Acura b18c1 that went through just as much oil and spun waaaaay faster but cam never wore like this. Anyway. Head was all done by shop. They took off a skin. I torqued it down according to Bentley applying torque then degrees. I guess I need to get a leak down tester. Or take it to a shop.
    I called machine shop and he said if it wasn’t sealing it’d be throwing codes. He said to set number 3 at max lift to make sure the lifter has bled out completely. 1) I thought hydro valves weren’t adjustable-what is he talking about? 2)it’s idled for long enough to heat up a couple times so oil should have made it through every orifice by now.
    I have a sinking feeling head wasn’t done right.
     
  8. MCS02

    MCS02 Moderator
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    The shop I worked for long ago used a machine shop that did most people in the area race engines. They had one of the best reputations they were very good. Every once in a wile something was not right but they would always take care of it. I am not saying they didn't do their job but don't rule anything out.
    The cam, are you saying its bad? if so change it, then recheck your numbers. AllMag https://www.allmagautoparts.com is a great place to get used parts. To point one they are hydraulic, too many cars dancing in my head.
     

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