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96 Vortec stumble/miss after changing intake gasket. UPDATE Problem solved.

Discussion in 'The Garage' started by MOABDADC22, Feb 27, 2003.

  1. MOABDADC22

    MOABDADC22 1/2 ton status

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    I just got done changing the intake gasket /forums/images/graemlins/angryfire.gif /forums/images/graemlins/angryfire.gif on my 96 Tahoe (5.7 Vortech.) Now it has a very noticible miss. The "Check Engine" light flashes on/off at a steady rate.

    All hoses/wires are in the correct spot. I have sprayed the intake with carb cleaner to check for a leak with none found.

    I did get the distributor 180 degrees off on the first attempt (DUH....) but pulled it and put it in the correct spot. I am pretty sure that the base timing is set right at 0 degrees. Is this correct?? I guess I could go fire it up and turn the distributor a little and see if that cures it. If it does.......how do I clear the trouble codes??

    Any help would be greatly appreciated. /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif
     
  2. MOABDADC22

    MOABDADC22 1/2 ton status

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    Re: 96 Vortec stumble/miss after changing intake gasket. HELP

    I forgot to add that the engine runs pefectly smooth for about the first 2-3 seconds after I start it, then it develops the miss.

    It ran like a top before I changed the gasket.
     
  3. 87GMCJimmy

    87GMCJimmy 1/2 ton status

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    Re: 96 Vortec stumble/miss after changing intake gasket. HELP

    Get it scanned, when I did my intake I forgot to hook up the cam position sensor. It ran Ok with out it but you could tell it wasn't running right and of course the check engine light was on. The computer will more then likely tell you whats wrong.


    Mike
     
  4. Mr.Chevy4x4

    Mr.Chevy4x4 1/2 ton status

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    Re: 96 Vortec stumble/miss after changing intake gasket. HELP

    Sounds like you didn't get a good seal with the new gasket. Sounds like a vacuum leak to me.



    Mike
     
  5. 3car

    3car 1/2 ton status

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    Re: 96 Vortec stumble/miss after changing intake gasket. HELP

    disconnect neg.battery terminal for 15 seconds or so to clear trouble codes.
     
  6. bigbluek20

    bigbluek20 1/2 ton status

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    Re: 96 Vortec stumble/miss after changing intake gasket. HELP

    Just to verify the intake gasket (although it sounds like you have), try unplugging the Mass Air Sensor (I have a leaky intake on the car, really smooths it out when unplugged).

    Check for crossed spark plug wires, make sure you plugged all the stuff in around the distributor (some of those are tough to see), loose grounds, might also verify temp sensors.

    The timing is computer controlled. You only need to have it close. I can scan the pics from the factory shop manuals if you need (kinda weird timing procedure compared to the days of yore). But if it is running at all, that should be okay.

    Make sure you got the crank sensor plugged in as well... just trying to remember those obscure "out of the way" ones.

    How about fuel pressure? Kinda thinking out loud... hope it helps.
     
  7. MEPR

    MEPR 1/2 ton status

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    Re: 96 Vortec stumble/miss after changing intake gasket. HELP

    well ill ask my auto shap techer tomarow in class for ideas. You wont wehant to unplug the bat untill you get the thing fixed as it will clear the codes and you may not whant to wait for the comp to flash em agian, and sometimes they dont even flash again.
     
  8. MOABDADC22

    MOABDADC22 1/2 ton status

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    Re: 96 Vortec stumble/miss after changing intake gasket. HELP

    OK, I scanned the codes with an OBDII and got P0102 (Mass Air Flow sensor Circuit Low Frequency) and P0304 (Misfire on #4 cylinder). soooooo....I am thinking that the # 4 intake gasket area did not seal/seat good enough and that is causing the MAF to detect air leaking in and then causing the #4 to misfire??

    Am I way off base or what??? I will probably buy another gasket and start over. (At least now I know that I can change the gasket in under three hours) /forums/images/graemlins/thumb.gif

    Thanks for the replies /forums/images/graemlins/deal.gif /forums/images/graemlins/deal.gif.......keep them coming since I will read them again in the morning. /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif
     
  9. ZonkRat

    ZonkRat 1/2 ton status

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    Re: 96 Vortec stumble/miss after changing intake gasket. HELP

    Be sure to torque in the right order.That can cause leaks on those motors. /forums/images/graemlins/thumb.gif
     
  10. Mr.Chevy4x4

    Mr.Chevy4x4 1/2 ton status

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    Re: 96 Vortec stumble/miss after changing intake gasket. HELP

    Be careful not to overtighten the intake manifold bolts! They only requires 15 Ft.Lbs. of torque. If you overtighten them you will distort the new gaskets and they will leak.



    Mike
     
  11. loudnowlouder

    loudnowlouder 1/2 ton status

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    Re: 96 Vortec stumble/miss after changing intake gasket. HELP

    [ QUOTE ]
    Be careful not to overtighten the intake manifold bolts! They only requires 15 Ft.Lbs. of torque. If you overtighten them you will distort the new gaskets and they will leak.

    [/ QUOTE ]

    i completely agree, 15 doesnt feel like much at all, but thats what it needs to be at, get the torque wrench out for this one. i overtorqued my vortec once and the intake gasket had to come out the next day.
     
  12. MOABDADC22

    MOABDADC22 1/2 ton status

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    Re: 96 Vortec stumble/miss after changing intake gasket. HELP

    Well, I bought another gasket and changed it again. I was able to do it in about 2 1/2 hours this time. /forums/images/graemlins/thumb.gif

    I am 99.9999% certain that the upper plastic half of the manifold was not torqued down to the aluminum half of the manifold properly.

    But, since I was not 100% certain that the intake gasket was not the culprit....I changed those again too (I already had the parts.) It runs like a champ now..........again.

    Thanks for the input. I appreciate it. /forums/images/graemlins/thumb.gif
     

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