rough idle '96 960

Discussion in 'Volvo 960' started by James B., Sep 27, 2010.

  1. James B.

    James B. Guest

    Just wondering what would cause a random misfire at idle. Engine is
    fine when driving.

    No vacuum leaks, wiring harness and coil packs okay, compression fine.

    Any suggestions to what else I should look at?
    James B., Sep 27, 2010
    KellySueVolvo960 likes this.
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  2. James B.

    James Sweet Guest

    You just listed all the things I'd normally check first. How are the
    spark plugs? Maybe time to have the fuel injectors cleaned?
    James Sweet, Sep 27, 2010
    KellySueVolvo960 likes this.
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  3. Water in the tank or bad fuel.
    Airport Shuttle, Sep 27, 2010
  4. James B.

    James Guest

    Could all six injectors go bad? At the same time?
    OBD throws misfire on all six, plus random misfire. Keep in mind that
    when driving, engine runs fine. No sputtering, missing, fuel smell,
    James, Sep 28, 2010
  5. James B.

    James Sweet Guest

    Well not so much go bad, as just gradually get dirty, it's pretty common
    for the whole set to get about the same amount of contamination because
    they all pass about the same amount of fuel from the same source.

    My first guess would have been vacuum leaks, but you say you've got that
    covered. Could also be something with the ignition, but you say the
    coils all check out fine. I suppose it could be a bad ignition module,
    does a single module drive all the coilpacks on those? Since it's across
    all six cylinders, it's almost certainly something that deals with all
    of them. How about the fuel pressure regulator? Fuel pump issues? Does
    the 960 use a pre-pump in the tank with a main pump under the car, or
    just a single main pump? Does the symptom get worse when the tank is low?

    The most likely thing still comes back to vacuum leaks. There are
    countless places for a leak, have you checked everything? Brake booster,
    air intake plumbing, crankcase ventilation, vacuum reservoir for the
    HVAC system. Air mass meter is another possibility, know anyone else
    with a 960 you could try a swap with?
    James Sweet, Sep 28, 2010
  6. James B.

    James Guest

    I ran some seafoam thru the gas; I'm assuming that cleaned the

    Still has a rough idle :(

    Where is the ignition module in this car?
    James, Sep 28, 2010
  7. James B.

    James Sweet Guest

    That can help a bit, but to do a thorough job and know the results, the
    injectors have to be pulled and run through a testing machine and
    ultrasonic cleaner.

    No idea where the ignition module is on those, I've never worked on a 960.
    James Sweet, Sep 29, 2010
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