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Thread: Engine bucking issue

  1. #1
    Join Date
    May 2004
    Location
    Marlton, NJ
    Posts
    136

    Engine bucking issue

    Car starts fine: when you accelerate gradually it's fine. But when you hit the throttle to accelerate and it kicks down it bucks violently until you take your foot off . It did it once or twice in the beginning. Now it's all the time. Replaced fuel pressure regulator. No affect. Also, no codes or check engine light on. Ideas????
    1990 X7 auto
    Last edited by 90redsc; 05-08-2017 at 07:56 PM. Reason: Added info

  2. #2
    Join Date
    Dec 2007
    Location
    Salem, OR
    Posts
    6,294
    Done anything w/plugs and wires lately?

    Done any engine cleaning recently?

    See any evidence of rodent nesting?

    How old is the fuel?

    Checked the harmonic balancer?

  3. #3
    Join Date
    May 2004
    Location
    Marlton, NJ
    Posts
    136
    Nothing with plugs or wires
    No animals
    No eng clean
    Dampner is ok

  4. #4
    Join Date
    May 2004
    Location
    Marlton, NJ
    Posts
    136
    Fuel is new

  5. #5
    Join Date
    Dec 2007
    Location
    Salem, OR
    Posts
    6,294
    Does the tach jump around?

    How many miles on plugs/wires?

    Any mods?

    Manual or auto trans?

  6. #6
    Join Date
    May 2004
    Location
    Marlton, NJ
    Posts
    136
    Tach jumps until you take foot off throttle
    6k on plugs and wires

  7. #7
    Join Date
    May 2004
    Location
    Marlton, NJ
    Posts
    136
    No modifications

  8. #8
    Join Date
    May 2004
    Location
    Marlton, NJ
    Posts
    136
    Auto trans

  9. #9
    Join Date
    Dec 2007
    Location
    Salem, OR
    Posts
    6,294
    Most times w/these cars, plug wires are the issue when you see heavy miss/bucking.

    I'd go over them carefully to be sure they're still fully seated - as hard as that can be to do.

    Might want to search here on tach jumping, just to be familiar w/that issue and it's causes.

  10. #10
    Join Date
    May 2004
    Location
    Marlton, NJ
    Posts
    136
    I'll check k them. Thanks

  11. #11
    Join Date
    May 2002
    Location
    Dallas, TX
    Posts
    5,641
    I'd vote for plug wires.. not seated fully.

    But something else you can do is to disconnect the cam sensor. See if that clears it up. Takes multiple tries to start the car, but once its running it will run fine. If the problem goes away, replace the cam sensor.

  12. #12
    Join Date
    May 2004
    Location
    Marlton, NJ
    Posts
    136
    I'll try that also

  13. #13
    Join Date
    Apr 2007
    Location
    New Orleans, LA
    Posts
    1,957
    sounds like my original 90 sc I got from jersey back in 08, the problem on mine was that one of the plug wires was melted by the exhaust and the coil was on its way

    replaced both and it ran perfect, up until the crank split

  14. #14
    Join Date
    May 2004
    Location
    Marlton, NJ
    Posts
    136

    Wires

    Any particular brand of wires you recommend?

  15. #15
    Join Date
    Oct 2012
    Posts
    34

    Plugs and wires

    Thanks millions guys. New plugs and wires did the trick. Runs great!

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