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Thread: E34 engine loses power @ 4500 RPM

  1. #1
    Join Date
    Aug 2005
    Posts
    1

    Default E34 engine loses power @ 4500 RPM

    Engine runs strong til 4500 RPM, then power fades abruptly.
    Running thru the gears (5 Speed Man. Trans), engine runs superbly, then at 4500 it hits a wall. What has been replaced in the last year; new fuel pump, fuel pres regulator, oxygen sensor, & catalytic convertors. Rebuilt engine has 20,000 miles on it, in a 92 525i with 95,000 miles.
    Has anyone experienced a similar problem or have an idea what might be causing it?
    Thanks in advance!

  2. #2
    Join Date
    May 2004
    Location
    Japan
    Posts
    9,250

    Default

    Fuel filter, rotor+disty cap come to my mind.

  3. #3
    Join Date
    Jul 2005
    Location
    Exeter, Devon, UK
    Posts
    106

    Default

    check the injectors as well... mine had a slight blockage in one... also check HT leads, distributor and rotor arm...

  4. #4
    Join Date
    Dec 2003
    Posts
    571

    Default

    Could just be something simple like the air filter.

  5. #5
    Join Date
    Feb 2005
    Location
    Richmond, TX
    Posts
    620

    Default

    Quote Originally Posted by shogun
    Fuel filter, rotor+disty cap come to my mind.
    No rotor and cap on an M50

    1988 M3 - Track rat
    1989 325iC
    1995 530iM
    2000 323iT - UUC BBK, PSS9 Coilovers
    2005 GMC HD Crew

  6. #6
    Join Date
    Jan 2004
    Posts
    4,150

    Default If its not the cat plugged up again then i would check one or more of the

    coils for poor output, someone else had that same problem with an m50 and it turned out to be a couple of bad coils....






    Quote Originally Posted by e34fun
    Engine runs strong til 4500 RPM, then power fades abruptly.
    Running thru the gears (5 Speed Man. Trans), engine runs superbly, then at 4500 it hits a wall. What has been replaced in the last year; new fuel pump, fuel pres regulator, oxygen sensor, & catalytic convertors. Rebuilt engine has 20,000 miles on it, in a 92 525i with 95,000 miles.
    Has anyone experienced a similar problem or have an idea what might be causing it?
    Thanks in advance!

  7. #7
    Join Date
    Oct 2004
    Posts
    3,395

    Default

    Quote Originally Posted by Bill R.
    coils for poor output, someone else had that same problem with an m50 and it turned out to be a couple of bad coils....
    That's what I was thinking....restricted flow at the cat. best, whit

  8. #8
    Join Date
    Feb 2005
    Location
    Richmond, TX
    Posts
    620

    Default

    Quote Originally Posted by lowell
    That's what I was thinking....restricted flow at the cat. best, whit
    He replaced the cats. Coils should cause a miss at idle if they are going bad.

    1988 M3 - Track rat
    1989 325iC
    1995 530iM
    2000 323iT - UUC BBK, PSS9 Coilovers
    2005 GMC HD Crew

  9. #9
    Join Date
    Jan 2004
    Posts
    4,150

    Default Baloney, even though he replaced the cats if there's a

    problem such as unburnt fuel it will kill the new cats very quickly. And typically a weak or bad coil will have more than enough energy to light the mixture at idle when with the throttle bore is closed. But not so when accelerating under load.








    Quote Originally Posted by brodee
    He replaced the cats. Coils should cause a miss at idle if they are going bad.

  10. #10
    Join Date
    Dec 2003
    Location
    Eastern Tennessee USi
    Posts
    14,839

    Default

    yep the old blow the spark out in high wind theory.

    I would check them (coils) first because even if you replace the cats your gonna dump more raw fuel in there and kazam! just like magic youll be asking the same question a month from now.

    OT: I used to be on a forum where guys would have super powerful ignition systems getting high speed miss...chasing things and spending thousands of dollars and of course I wouldnt get the credit for being nut on in the first place. You have high compression and a miss at 7000rpms...lets see here, whats the plugs gapped at .045...LOL Try .030...that would start all kinds of stuff going. I dont need to gap them that small I have 30 bazillion volts...whatever man.
    95 E34 530I V2.37
    ===========
    Those who make peaceful revolution impossible will make violent revolution inevitable.

    John F. Kennedy

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