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backfiring(please help)

This is a discussion on backfiring(please help) within the General Help forums, part of the LSx Technical Help Section category; for about the past week when i try and start my car, it backfires and wont turn over on the ...

  1. #1
    Impounded
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    May 2008
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    NBM
    99 z28

    Question backfiring(please help)

    for about the past week when i try and start my car, it backfires and wont turn over on the first crank. the 2nd crank it starts right up. yesterday, as well as today, when i went to start my car to head home from work, i put the key in the ignition, went to turn it over, sounds like its trying to start but nothing but a loud ass pop(backfire). seriously, it sounded like a fucking shot gun. when it does it(backfire) it seems like it gets louder and louder. it does not backfire when im driving or after i decelerate from accelerating. also, its not every time i try and start my car. i'd say every 3rd time i go out to start my car is when everyone around me hits the pavement as soon as i turn it over and a LOUD ass pop happens. its fucking pissing me off and embarrassing.

    side note: dont know if this could have anything to do w/it. about 2 weeks ago i had my muffler cut off right behind my rear axle and was running open exhaust(no cats and no muffler). this started about a week ago. it did not start as soon as i had my muffler cut off. just out of the blue this shit is happening. i was hoping it had something to do w/me cutting off my muffler(not enough backpressure???) so yesterday i had it welded back on. and its still doing it. WTF????

    any ideas/suggestions????

    thanks in advance.

  2. #2
    Junior Member 1 TRANS AM's Avatar
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    BLUE
    02 TRANS AM

    Mabye the crank sensor, or cam sensor. Sounds like the pcm does not know when to fire.

  3. #3
    Junior Member Khaotic's Avatar
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    Red
    2000 SS Camaro

    Plugs

    I would take a look at your plugs

  4. #4
    Member edbird's Avatar
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    red
    1999 trans am convert

    This is from the service manual:
    Backfire
    Checks
    Actions

    DEFINITION : Fuel ignites in the intake manifold or in the exhaust system, making a loud popping noise.

    Preliminary Checks
    Refer to Important Preliminary Checks Before Starting in Symptoms .
    Search for bulletins.
    Inspect the PCM grounds for being clean, tight and in the proper locations. Refer to Engine Controls Schematics .

    Fuel System
    Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    Test for a restricted fuel filter. Refer to Fuel System Diagnosis .
    Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    Inspect that each injector harness is connected to the correct injector/cylinder according to the firing order (firing order: 1-8-7-2-6-5-4-3). Relocate injector harnesses as necessary.

    You are not throwing any codes? No SES light?

  5. #5
    Impounded
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    99 z28

    first, my SES light always stays on(due to me ditching my cats). because of that, i routinely have my car scanned at auto zone atleast 2-3 times a month to make sure its not throwing any other codes besides the one i know about(po420). i had my car scanned at auto zone yesterday and heres the list of codes:


    po305-cyclinder misfire detected-cylinder # 6. the pcm has determined that a misfire has occurred in cylinder #6.

    po342-cam senson condition. the pcm has determined that the voltage signal from camshaft position sensor "A" is too low for the current engine operating conditions.(bank 1 or single sensor)(bank1 identifies the location of cylinder #1, while bank 2 indentifies the clinders on the opposite bank). (as mentioned by 1 TRANS AM)-thanks for the reply.

    po171-fuel trim bank one condition. the pcm has determined that during testing, the fuel system for bank1 was too lean. (bank 1 identifies the location of cylinder #1, while bank 2 indentifies the cylinders on the opposite bank).

    po332-knock sensor condition. the pcm has determined that the voltage signal from knock sensor 2 is too low for current engine operating conditions. (bank 2) (bank 1 identifies the location of cylinder #1, while bank 2 identifies the cylinders on the opposite bank).

    ^^^this is from the printout they gave me at auto zone.


    the earliest i can get it to my mechanic is wednesday. what do you guys think? is it safe to drive until then? or will i just be doing more harm than already done? it is my only means of transportation. thanks for the replies.

  6. #6
    Member edbird's Avatar
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    1999 trans am convert

    I think I would do everything I could to avoid driving it.

  7. #7
    Impounded
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    im not driving it anymore till i have to drop it off w/my mechanic. my wife just got a new car so ive been cruisin in that. '04 altima, black w/dark tint. really clean, brand new tires. if i ever have to get rid of my Z(fat chance), i would more than likely get one of those. get to take my dads hot rod to work monday. that'll be cool.


    i just hope its nothing major so i dont have to spend an ass load of cash to have it fixed.

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