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Misfiring ALOT

This is a discussion on Misfiring ALOT within the General Help forums, part of the LSx Technical Help Section category; This is going to be a fairly long post because there could be multiple issues involved with the random misfiring. ...

  1. #1
    Junior Member
    Join Date
    Nov 2009
    east coast

    1999 firebird Formula

    Misfiring ALOT

    This is going to be a fairly long post because there could be multiple issues involved with the random misfiring. I am using an aeroforce interceptor gauge to monitor each cylinders misfire. The gauge is showing me multiple random misfires on all 8 cylinders in no perticular pattern. At some points it shows any one clyinder having between 6 and 8 misfires. Other cylinders are also showing misfires at the same time. Most of this misfiring is occuring when giving it gas and when i let off of the gas quickly. There is no SES light and no codes.

    Last month I have a 3500 stall put in the car and the shop that put it in had the O2s on the headers swapped which caused all sorts of misfires with an SES light. After checking all of the spark plug wires he finally checked the O2s and swapped them and the car ran much better. At that point in time i did not have the aeroforce gauge and was not able to check if any misfires were going out with out an SES light after the o2s were swapped back correctly.

    The car has always ideled rough but does so now alittle more then usual. Also since the stall the rpms fluxuate considerably on their own when i am backing up. For example the car idels around 500RPM according to the dash. when i give it gas to back up the rpms rise and then when i let off the rpms drop below 500 and then shoot a couple hundred past 500 hundred before settling back to normal. If i look at the aeroforce gauge a misfire on multiple cylinders usually comes up stays on the gauge for a few seconds and then goes away. Then a couple minutes later it will show misfires again. Does this drop in RPM represent a misfire?

    The day that i got my car back with the O2s swapped i most definitly felt it misfiring. It was jerking, bucking, and stalling. But now the guage is says it is misfiring i am not feeling anything close to that.

    Some possible things that i can think of that might be causing the issue are: I need to get my frost tune redone because i got it done before i got the stall put in, my 84,000 mile sparkplug wires are shot, my 2,000 mile ACDelco spark plugs are shot, my 2,000 mile Bosch 1331 O2 sensors got burned up when they were incorectly swaped after the torque converter install, or the aeroforce gauge is not representative of what is actually happening. Any help in determining the cause of this issue would be greatly appreciated. Thanks.

    Here is some information that i got form my aeroforce gauge:

    short term fuel trim 0 to -3 bank 1
    short term fuel trim 0 bank 2
    long term fuel trim bank 1 .7
    long term fuel trim bank 2 -.7
    02 bank 1 65 to 810 mv
    02 bank 445mv (assuming this is after cats that were deleted)
    02 bank 2 85 to 810 mv
    battery 13.7V
    TCC slip 655
    RPM in park 650
    RPM in gear 540
    MAP LB/m 0.72
    MAF frequency 2287
    Ignition advance 17.5
    PW bank 1: 3
    PW bank 2: 3

  2. #2
    O U 8 1 2 Spaz's Avatar
    Join Date
    Nov 1999
    over here...

    []D [] []V[] []D
    1999 trans am

    did you plug everything back in??? sounds like something was left unplugged... is teh maf plug connected etc etc...

  3. #3
    Junior Member
    Join Date
    Nov 2009
    east coast

    1999 firebird Formula

    i checked all of the spark plug wires and connectors and everything looks fine. Do any of my numbers from the gauge look way off?

  4. #4
    Moderator Cutlass's Avatar
    Join Date
    Apr 2008
    Madison, WI

    1999 Formula WS6 M6-sold
    2001 Silverado Z71

    high stall converters sometimes/often times screws up the misfire detection. What you are seeing on your gauge probably isn't a real misfire. You might need some tuning to desensitize the misfire detection

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