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Loud Bang noise in cold morning start 850 1995

posted by  HO on  Sun Jan 23 05:59 CST 2011
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last visit: Tue Aug 12 14:01 CST 2014
[RELATED]

My car exhibits a loud bang noise due cold morning start. It sounds like an explosion inside the engine. It only happens to the very first cold start of the car. Subsequent start of the car sound normal (no loud bang noise). In previous winter, cold morning start always a bit louder than warm morning start. However, this year is very loud even my daughter asked me what is happening to the car when she is standing nearby.

What could it be to cause this loud bang noise under the hood ? My car just gets passed 240k miles. Any suggestion is appreciated.

Thanks,

Ching-Ho Cheng
--
1995 855 NA, Bilstein Strut & Shocks, Volvo Protective Grill, K&N Filter, E-Code Lens, ClearCorner Light, Alpine CD-Changer, AutoDim RearView Mirror, 6000K HID








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    Loud Bang noise in cold morning start 850 1995

    posted by  KlausC on  Sun Jan 23 16:30 CST 2011
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    last visit: Fri Oct 24 10:15 CST 2014
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    When is the last time you checked your spark plugs? If they are worn, they might not be firing as well with the extra rich mixture, causing a flame in the exhaust manifold when the mixture finally ignites.

    You also need to check the fuel pressure regulator, if there is any fuel in the vacuum line that goes from the FPR to the vacuum tree.

    Klaus
    --
    Always willing to listen, just not able to take direction.








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      Loud Bang noise in cold morning start 850 1995

      posted by  HO on  Mon Jan 24 08:08 CST 2011
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      last visit: Tue Aug 12 14:01 CST 2014
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      Klaus,

      I changed the spark plugs along with wire, distributor cap and distributor rotor not long ago. This loud band noise was first started in cold morning in Boston (around Autumn time) even before the spark plugs/wire/distributor cap/rotor change. So spark plugs/wire/distributor cap/rotor change did not change the symptom.

      How do I check this vacuum line between FPR and vacuum tree ?

      Thanks,

      Ching-Ho Cheng
      --
      1995 855 NA, Bilstein Strut & Shocks, Volvo Protective Grill, K&N Filter, E-Code Lens, ClearCorner Light, Alpine CD-Changer, AutoDim RearView Mirror, 6000K HID








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        Loud Bang noise in cold morning start 850 1995

        posted by  KlausC on  Mon Jan 24 12:23 CST 2011
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        last visit: Fri Oct 24 10:15 CST 2014
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        The FPR is on the passengerside of the fuel rail, next to the injectors. The vacuum line goes from there towards the throttle body, you should be able to see it without removing anything as it goes across the intake manifold.

        While you are there, take the cover off the throttle cable and inspect the other lines that go to the vacuum tree for cracks, etc. The nipple covers should all be snug.

        Klaus
        --
        Always willing to listen, just not able to take direction.








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    Loud Bang noise in cold morning start 850 1995

    uid 5322's pic
    posted by  alschnertz on  Sun Jan 23 10:38 CST 2011
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    last visit: Fri Oct 24 10:32 CST 2014
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    If it's a quick bang or clunk, I'd first check the exhaust system for loose hangers or shields.







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      Loud Bang noise in cold morning start 850 1995

      posted by  HO on  Sun Jan 23 15:59 CST 2011
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      last visit: Tue Aug 12 14:01 CST 2014
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      It is a quick bang noise right at the moment when engine fired up. If this is related to exhaust shield or hangers, then how come subsequent start up has no quick bang noise ?

      Thanks,

      Ching-Ho
      --
      1995 855 NA, Bilstein Strut & Shocks, Volvo Protective Grill, K&N Filter, E-Code Lens, ClearCorner Light, Alpine CD-Changer, AutoDim RearView Mirror, 6000K HID








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        Loud Bang noise in cold morning start 850 1995

        uid 5322's pic
        posted by  alschnertz on  Mon Jan 24 11:21 CST 2011
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        last visit: Fri Oct 24 10:32 CST 2014
        [RELATED]

        Just a guess that things may have heated up and expanded just enough to not cause the bang after it's been started once.

        Or that the car starts easier after it's warmed up - less cranking, less fuel injected leading to a less powerful explosion on that 1st crank.

        Maybe you could describe the bang in more detail.







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