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960 & S90 rough engine S90-V90 1997

posted by  doctim on  Thu Oct 21 06:07 CST 2004
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I have a '97 960 and a '98 S90 with the same B6304 engines. They are running rough when idling, like they missfire and then recover. The local mechanic says that each cylinder has its own coil and he needs to find out which one is misfiring. Are these coils known to cause misfiring (both motors mileage in the 130k range)? Should they all just be replaced?
Thanks, doctim.








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    960 & S90 rough engine S90-V90 1997

    uid 19's pic
    posted by  jbowers on  Thu Oct 21 09:49 CST 2004
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    last visit: Sun Jan 22 13:49 CST 2012
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    Have him read the codes from the ECU out of the OBD-II socket. We can tell you which cylinder is missing.

    Based on my personal experience, my first place to check is the intake manifold gasket around cylinder #1, (first one from the radiator).

    If the gasket is redish-orange, it is the frist design and WILL fail sooner or later. If greenish-aluminum it should be OK but check anyway.

    Usually a weak spark will show under load, not at idle. What are this mechanic's quaalifications? If he doesn't have a code reader, he can't work on this car unless you want to pay for a lot of expensive parts while he tries to hit the right one.
    --
    '96 965 with 16' wheels at 120K. Had '85 745 Turbo Diesel for 200K.








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    960 & S90 rough engine S90-V90 1997

    uid 25930's pic
    posted by  VHT on  Thu Oct 21 06:22 CST 2004
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    Could be a leaking intake manifold gasket. Spray a little carb cleaner near the gasket while idling and notice any change.
    --
    VHT 92 965








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      960 & S90 rough engine S90-V90 1997

      posted by  someone claiming to be jrroberson on  Fri Oct 22 00:07 CST 2004 [RELATED]

      Have you tried cleaning the idle control valve which is hooked to the breather tube between the air mass flow meter and the throttle. That can smooth out an idle problem. I would also look at the throttle body itself and give that a good cleaning as well. You may have a lot of carbon built up in the engine also.There is a machine called Motor vac that hooks up to the fuel rail that will clean the injectors,intake valves combustion chambers,exhaust valves even your 02 sensors, If your in an area that has one of these go by and have it done can't do anything but good with the mileage you have. When was the last time you changed your 02 sensors? They are to be replaced at 100m.
      They are quiet costly in these cars.
      Good Luck
      Poolman







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