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Help with M42 running issues

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    Help with M42 running issues

    I recently installed a head on a 91 318is m42, Did the chain guides also. Car was brought to me on trailer. Now with everything together, it will start but not respond to the throttle properly or idle. All air hoses were replaced are seem tight. I can find no obvious air leak. The stomp test says 1215 or airflow meter. Tried another one no difference. The TPS switch seems ok, it has variable resistor as the throttle moves. The funny thing is when I disconnect the tps switch and start the car, it pegs to redline and the key must be turned to stop it. I am at a loss with this. Tomorrow I'll go back over everything again and see if I missed any thing. Any ideas?? The crank and cam sensors must be ok as it starts ok but won't react to the pedal at all, won't hold a steady rpm anywhere.
    Greg Mierz
    Puget Sound BMW club member since 1978
    Board Member for over 26 years now retired
    1969 2002 ti since 1974
    1986 325is my current daily driver
    GMTechnic BMW consultation service BMW mechanical services at less than independent shops or dealer

    #2
    I bet you've got a massive vacuum leak. Double check all the hoses under the intake manifold.

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      #3
      It was a air leak but not the hoses. The owner put the manifold on and got a locating dowel jammed and the intake manifold wasn't seated near #4 cylinder. Remove the uppper manifold to check all the hoses and discovered the leak. Fixed it and all is well. Live and learn, never assume it is right until you verify it is right.
      Greg Mierz
      Puget Sound BMW club member since 1978
      Board Member for over 26 years now retired
      1969 2002 ti since 1974
      1986 325is my current daily driver
      GMTechnic BMW consultation service BMW mechanical services at less than independent shops or dealer

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