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Misfiring/backfiring '97 T/A

This is a discussion on Misfiring/backfiring '97 T/A within the LT1 forums, part of the Vehicle Specific category; My cousin has a '97 Trans-am. Tha mods are an LT4 hot cam, LT4 knock sensor, powerdyne supercharger with a ...

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    Misfiring/backfiring '97 T/A

    My cousin has a '97 Trans-am. Tha mods are an LT4 hot cam, LT4 knock sensor, powerdyne supercharger with a 6lb pulley, Kook stepped headers, High flow cats, Flowmaster cat-back system, custom PCM tune.
    The problem we are having is that it will intermittently misfire/ping/backfire. Some days you fire it up and it runs fine until it warms up, other days it runs horrible right away. When it is misfiring badly it picks up a bad engine knock/rattling sound. I pulled the code with a generic OBDII scanner and got the following codes.

    P0300-random/multiple misfires
    P0103-mass or volume circuit high input
    P0400-egr flow malfunction

    I thought maybe the P0103 was because the charger is creating a higher airflow through the MAF, but it didn't have a check engine light for a few months after we supercharged it.

    I appreciate any help that you can give a newbie to this site.
    Thanks

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    Member dkishton1486's Avatar
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    optispark maybe? well atleast for hte misfire

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    Is there any way to test the opti-spark rather than just changing it out and hoping it fixes it? I know it won't set a code, but can I check some voltage/resistance values?

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    Member dkishton1486's Avatar
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    To be honest I wouldnt know if you can test it or not but also maybe he can change his plugs and wires too?

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    Quote Originally Posted by dkishton1486
    To be honest I wouldnt know if you can test it or not but also maybe he can change his plugs and wires too?
    Plugs & wires are less than a year old and don't have that many miles on them. I may pull one out just to check anyway. The odd part is that it doesn't do it all the time. It will occaisionally run really well.

  6. #6
    1BADLT1
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    Maybe not the Mass Air but definatly the map. The Map sensor calculates fuel by judging pressure in the intake. I am not sure if it needs to be changed if you get a supercharged car, but it seems like that could cause a problem.

  7. #7
    baconmach
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    from what ive seen on the dyno.....it sounds like your tuner or your mail order tune..
    1may be a lil to lean for what your set up is
    2may be to much timing
    3what fuel are your running

    a quick help might be to try race fuel to see if the pinging stops.....

    because it sounds like your tune.....ive never heard of a mire calibrated mass air...causing detonation....lol

    id like to pull the old opti spark story but.....my gd friend has ur car...with 50k miles....sounds a lil to early for u to be having opti spark bugs...unless ur already hittn 100k.......

    THE BEST ADVICE I DUNNO WHY NOONE SAID THIS....IS TO STOP DRIVING THE CAR...BEFORE U HAVE NO CAR..!!! LOL
    nice set up non the less

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    Quote Originally Posted by baconmach
    from what ive seen on the dyno.....it sounds like your tuner or your mail order tune..
    1may be a lil to lean for what your set up is
    2may be to much timing
    3what fuel are your running

    a quick help might be to try race fuel to see if the pinging stops.....

    because it sounds like your tune.....ive never heard of a mire calibrated mass air...causing detonation....lol

    id like to pull the old opti spark story but.....my gd friend has ur car...with 50k miles....sounds a lil to early for u to be having opti spark bugs...unless ur already hittn 100k.......

    THE BEST ADVICE I DUNNO WHY NOONE SAID THIS....IS TO STOP DRIVING THE CAR...BEFORE U HAVE NO CAR..!!! LOL
    nice set up non the less

    Thanks for the answer. To answer a few of your thoughts:

    The charger has been on for about a year and up till now has been running really well.

    The car only has 17k on it

    We have only been running the car for diagnostic purposes, he has a truck for his daily driver

    I may try hooking my wideband up to get an idea where the fuel mix is at.

    As far as timing, could a bad Opti cause timing problems?

    Thanks

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    after you do that i would say replace both front o2s i also have a 97 ta and it turns out that i had the same problem and one of them was faulty but it wasnt to where it triggered a code.meaning it kept working in a range enough for the pcm to not throw a code but not enough to keep the a/f mixture correct. hope that helps......

  10. #10
    baconmach
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    a bad opti...would make the car run horribly....(bucking, backfiring , amazing loss of power.....or just not run...) but you would be the first ever Ive heard of to throw an opti at 17k......but....if it is.....you can most likly attribute it to a real bad leak in your water pump......if the cars leakn fluid....it would screw up the opti..........

    haha or if a certain some decided to change the thermostat...and made a huge mess.....(had this happen...lol) ask him if he put in a 160 stat.....

    wideband is a good start, or try to hit up a dyno guy that can do the lt1...most ive seen only do the ls1 edit...but the lt1 edit guys are around....just be careful...and get a hold of the a/f....

    gd luck....love to see the numbers on that thing to!!!!!

  11. #11
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    How about a random backfire through the exhaust? NO codes

    More common at 1500ish rmp

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    Senior Member 440 rwhp trans am's Avatar
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    Quote Originally Posted by baconmach View Post
    a bad opti...would make the car run horribly....(bucking, backfiring , amazing loss of power.....or just not run...) but you would be the first ever Ive heard of to throw an opti at 17k......but....if it is.....you can most likly attribute it to a real bad leak in your water pump......if the cars leakn fluid....it would screw up the opti..........

    haha or if a certain some decided to change the thermostat...and made a huge mess.....(had this happen...lol) ask him if he put in a 160 stat.....

    wideband is a good start, or try to hit up a dyno guy that can do the lt1...most ive seen only do the ls1 edit...but the lt1 edit guys are around....just be careful...and get a hold of the a/f....

    gd luck....love to see the numbers on that thing to!!!!!
    It could be the opti. if your supercharged and drive it up to high rpms that will kill a stock opti. I would sugest you to change the crank positioning sencor 2. mine whent bad and it was crazy how it ran but still did. and its only $20 bucks and easy to install.

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