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  1. #1
    VXRed
    Join Date
    17th February 2019
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    134

    Default Back firing under heavy acceleration

    Hi guys, yet another problem lol standard. As title says car is back firing 4-5 times in a row really quickly under heavy acceleration accompanied by a loss of power. Otherwise drives fine. Just had it mapped a month ago been fine since map until today when this started. Iím thinking spark plug and or gaps, or coil pack maybe? Or is the map running too rich? But it has been running well with the map for a month and this just started! It does feel under powered in 4/5/6 sometimes.


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  2. #2
    VXRed blooded Seanwebb68's Avatar
    Join Date
    31st July 2014
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    407

    Default

    Iíd start with spark plugs


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  3. #3
    VXRed
    Join Date
    17th February 2019
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    134

    Default

    Yea cheap first and then up from there I suppose. Is it correct that Astra h vxr runs the best on standard OE plugs, even when mapped etc? Iím stage 2 and does anyone know what the gaps should be, Iíve heard 0.7mm?


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  4. #4
    VXRed
    Join Date
    17th February 2019
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    134

    Default

    Or if anyone has any other ideas that are common for making this happen?


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  5. #5
    VXRed blooded Seanwebb68's Avatar
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    31st July 2014
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    407

    Default

    Yeah these are what youíre want

    The part number is 55562534 which are NKG PFR6T-G


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  6. #6
    VXRed blooded
    Join Date
    2nd April 2015
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    358

    Default

    See that's interesting. I just had my MOT done and the garage put in some new sparks. I was running with the standard/original Bosch plugs but i'm not sure what he's replaced them with. I've since installed a top hat, a new MAF (to cure a different issue) and just noticed that when boost comes in under hard acceleration it begins to backfire/judder?

    I suspect i'm having the same issue. Going to try it again tonight on the way to work and see if it wasn't just a one off.

    If it happens again, i'll check what sparks he's put in and probably replace them with some of the same Bosch ones or NGKs. Can't imagine that the coil pack has just decided to pack in. I've looked down in the engine bay and can't see any lose hoses that have blown off.
    Last edited by offender; 26th March 2019 at 04:23 PM.
    Astra H VXR | Stage 3 | 304 Bhp | Whiteline RARB | AEM cone filter | Direct Route | Airtec front mount intercooler | Cobra Sport 3" Exhaust non-resonated + Sports cat | Enhance Performance Top Hat

  7. #7
    VXRed
    Join Date
    17th February 2019
    Posts
    134

    Default

    Mine was the plugs. They were loose and battered so needed refreshing. Iím told they run best on the OEM plugs that I believe are ngk. Sounds like this may be your coil pack have you checked that?


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  8. #8
    VXRed blooded
    Join Date
    2nd April 2015
    Posts
    358

    Default

    Haven't checked anything yet. Just drove to work and got the same issue except the EML started flashing and gave me error codes for misfire and misfire in cylinder 2 (30001 and 30201). Given that it's on new plugs from a MOT I'll check them out and see what he's put in the car, can't imagine he'd stray from OEM parts but it's worth a check. I'll have to order a coil pack if the plugs don't change anything.

    I've had NGK plugs randomly fail on me before, it's why I switched to the Bosch ones. Throughout the time of being stage 3 the Bosch ones have been good for me but I'll have to wait and see what exactly is in the car now before I make a decision on what to do next
    Last edited by offender; 26th March 2019 at 09:58 PM.
    Astra H VXR | Stage 3 | 304 Bhp | Whiteline RARB | AEM cone filter | Direct Route | Airtec front mount intercooler | Cobra Sport 3" Exhaust non-resonated + Sports cat | Enhance Performance Top Hat

  9. #9
    VXRed
    Join Date
    17th February 2019
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    134

    Default

    Surely coil pack man common as ****


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  10. #10
    VXRacing ahead Gaz the gasman's Avatar
    Join Date
    4th October 2013
    Posts
    632

    Default

    Don't some people spend good money trying to make their car pop and bang?. You've got it as an added bonus for free.

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