Why does my truck miss fire badly when I first start it in the morning?

Discussion in 'Chevy C/K Truck Forum' started by Crispyt, Feb 2, 2012.

  1. Crispyt

    Crispyt Rockstar 100 Posts

    I have a 1995 C1500 Chevy with the 4.3L V6 engine. Its a TBI engine. The other day when I started it for the first time in the morning it skipped and miss fired really badly for about 30sec then it was fine. I used it all day and it started up normal every time and ran perfect. Then the next day after it sat all night it did the same thing as before only for the first start of the day then it was fine all day again. It sounds like its only firing on 4 cylinders when it miss fires. I have new plugs and wires in it, new fuel filter, cap and rotor. Also the fuel pump and strainer are only a year old. I checked vacume lines and they all seem fine. My personal thought is that it might be a bad ignition control module because it only does itonce in the morning then its perfict the rest of the day.Any ideas? Thanks for your time and help all!
  2. GMCErica

    GMCErica Rockstar 3 Years GMTC Chick 1000 Posts Platinum Contributor

    I hate when that happens.. LOL i got a few ideas:

    1) o2 sensor- could effect exhaust stream
    2) spark plugs, plug wires
    3) switch your coils around
    4) Cap & Roter
    5) Coolant Leak

    Make a list and start going through them.. GOOD LUCK!
  3. outalne94z71

    outalne94z71 Member

    one possibility is the coils used on these trucks are known for going bad and arc when there is moisture in the morning till the engine heat dries them out, you may be able to duplicate the issue by using a spray bottle of water on the coil once it starts running right and it should go back to the misfiring.
  4. Crispyt

    Crispyt Rockstar 100 Posts

    I tryed the water on the ign. coil but it didnt make a difference it still ran fine. It was also replaced less than a year ago. Its only miss firing for about 20-30 sec then its like all of a sudden fine.
  5. outalne94z71

    outalne94z71 Member

    i wonder if you have some lifters losing prime over night then? does it clatter at all when its misfiring?

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