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vortec 350 problem

This is a discussion on vortec 350 problem within the General Help forums, part of the LSx Technical Help Section category; I have a 350 vortec 96 truck. It has 158000 miles and has been maintained and always ran like a ...

  1. #1
    Junior Member
    Join Date
    Nov 2005
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    GA
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    BLACK
    2000 Camaro ss

    vortec 350 problem

    I have a 350 vortec 96 truck. It has 158000 miles and has been maintained and always ran like a champ. Now it has a misfire stumble between 1500 rpm and 4000 rpm. Mostly it does this when in overdrive or barely giving it gas and upon initial accelration.
    I have replaced the
    plugs, rotor, dist, plug wires, coil, throttle position sensor, egr, crank sensor, intank fuel pump and the injector on the misfiring cylinder. When the codes are scanned (with a cheap scanner ) it just shows a misfire on #1. When the truck is warming up it runs fine and gets worse as it reaches operating temp. The motor does not smoke at all and is original otherwise. The timing is nonadjustable. Anyone with a truck like this who conquered a similar problem?

  2. #2
    Senior Member
    Join Date
    Aug 2005
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    Windsor, VA
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    169

    LPM
    2000 SS

    Congrats on your mileage !

    Run compression/cyl leakdown tests (concentrate on #1) and let us know.

  3. #3
    Junior Member
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    Nov 2005
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    GA
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    BLACK
    2000 Camaro ss

    fixed!

    I put an ignition pick up coil on and the rpm band cleaned up. I took the dist out to inspect the gear wear and it was ok. I screwed up somewhere on my marks and couldnt get it cranked at first. I pulled up threads on timing and found a post explaining to line the damper mark with the tab on the timing cover. Very different than old school timing marks. Then line the rotor with #8 stamped inside dist housing edge. Took a few attempts but its got the kick in the pants back with no misfiring. Ses light came back on but I could be a degree or two off on the timing, or the tank of fuel cleaner possibly. Truck is still in excellent shape for the age and use it has seen. Thinking, Ill start restoring it back to new condition soon. Thanks for the help . I mostly got hints by reviewing all the old posts linked to timing.

  4. #4
    Junior Member
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    2000 Camaro ss

    info

    I pulled up the info on the fullsizegm.com forums site. LOTS AND LOTS of info and trucks galore. Chevy fullsize only.

  5. #5
    next i would check the valve springs for that cylinder and the wiring harrness for the injector.is the vortex batch fire or sequencial?if its batch try swaping electrical plugs on the injectors ,see if the problem moves.if its sequencial its very possible you have a PCM problem or ground trouble.maybe check the valve seals too.i've seen a bad seal foul a plug intermitenly but usually that happens on a cold start,then as the engine warms up the plug clears.what does the plug look like in that cylinder?compare it to the others maybe that will give you some kind of clue.did you consider extreme carbon buildup on the intake valves? i've seen that cause similair trouble to what you are having.bad valve seals will alow oil to drip on the intake valves where it burns causing extreme carbon buildup.enough to cause part throttle drivability problems.
    Last edited by YoMommasTA; 02-25-2006 at 03:33 PM.

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