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Thread: 525i help needed please !

  1. #1
    Join Date
    Apr 2006
    Posts
    7

    Default 525i help needed please !

    E34 525i 2.5 24v DOHC.

    The car starts and runs perfect most of the time.
    Every now and then after it has started in the morning it will run fine and then suddenly become sluggish.
    Pressing and holding the throttle flat it revs to +-3000 and then drops back down, then up again and back down, it will not rev up.
    Also driving it like that is impossible, pulling off is nearly impossible.
    When I unplug the Air sensor it runs better but heavy on fuel, sometimes that doesn't even help.
    Anything to try or test ???

  2. #2
    Join Date
    Oct 2005
    Location
    Durban, South Africa
    Posts
    398

    Default

    Does the engine shut off at all after revving to 3K?
    And how does it idle in that state? should be around 750 to 900 rpm I think.

    I would try and test or have a look at your fuel pump. I'm having similer problems with my 90 525i and I'm replacing the fuel pump. Which will fix my problem. Another thing, when was your fuel filter last changed?

    Once the car is warmed up, will it run fine or not?
    Car: BMW 525iA.
    Engine: M20.
    Trans: Auto.
    Year: 1990.

    Location: Durban, South Africa.

  3. #3
    Join Date
    Dec 2003
    Location
    Eastern Tennessee USi
    Posts
    14,839

    Default

    Agreed with Rob, change the fuel filters first, if still having problems hook up a fuel pressure guage to see where your at and go from there.
    95 E34 530I V2.37
    ===========
    Those who make peaceful revolution impossible will make violent revolution inevitable.

    John F. Kennedy

  4. #4
    Join Date
    Apr 2006
    Posts
    7

    Default

    Somedays it will be fine and not do it at all like today. Car ran beautifully today. Other days it just goes haywire.
    Will see if I can change the fuel filters this weekend.
    We thought it was temp related, when the car gets hot. But like today it was hot and nothing went wrong.
    Idling is a bit eratic when it does that.
    Switch it off and on a few times and it goes again.
    Other days you must sit and wait for it to come right, up to 2 hours sometimes.
    Might it be knock sensors or something ?

  5. #5
    Join Date
    Sep 2005
    Location
    southeastern, CT
    Posts
    54

    Default

    I had a similar problem on my 325i (same engine) and a new coil pack fixed everything. Do you have hesitation or bogging as well?
    If so you might want to check the coil packs/boots and plugs.
    Also might want to try cleaning the ICV.
    Also if the check engine light is on you should read the codes.

    89 535i/5
    90 535ia 158k
    90 Infiniti Q45 (sold)
    91 Sho (sold)
    94 530i/5 (sold)
    95 855 T5 @15psi boost

  6. #6
    Join Date
    Aug 2005
    Posts
    593

    Default

    Quote Originally Posted by gt90
    I had a similar problem on my 325i (same engine) and a new coil pack fixed everything. Do you have hesitation or bogging as well?
    If so you might want to check the coil packs/boots and plugs.
    Also might want to try cleaning the ICV.
    Also if the check engine light is on you should read the codes.
    Not to hijack the thread. I have a hesitation when pressing on a gas pedal. The car does not react, you wait for maybe a second and it picks up. Or I release the gas, press it a little slower.
    You had the same hesitation and new coil packs fixed it?
    1994 520i with M50 engine, manual transmission and air conditioner.
    VIN: GG45422

  7. #7
    Join Date
    Sep 2005
    Location
    Goulburn Australia
    Posts
    689

    Default

    I agree that it sounds like a fuel starvation problem. I've had similar with cars other than my E34. The junk inside the filters moves around. Some days it wont bother you other days it will clog up. Starting the car a few times and jolting the fuel from rest through the pump will stir the junk up.
    Cheers

    Wingman
    '89 525i/A Exec 193000kms
    '94 Subaru Liberty AWD Wagon
    Looking for Merc 300TE
    NSW, Australia

  8. #8
    Join Date
    Apr 2006
    Posts
    7

    Default

    When I unplug the Air sensor it runs better sometimes but then it smokes and is heavy on fuel.
    Going to change the fuel filters and check the spark plugs and wires.

  9. #9
    Join Date
    Aug 2005
    Posts
    593

    Default

    Is it safe to unplug the MAF while the engine is running?
    1994 520i with M50 engine, manual transmission and air conditioner.
    VIN: GG45422

  10. #10
    Join Date
    Sep 2005
    Location
    Goulburn Australia
    Posts
    689

    Default

    It would appear that your O2 sensor is working then (I assume that it is black smoke). Is there a 'miss' anywhere?
    Cheers

    Wingman
    '89 525i/A Exec 193000kms
    '94 Subaru Liberty AWD Wagon
    Looking for Merc 300TE
    NSW, Australia

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