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I have a 98 GMC serria 350 Vortec I had engine rebuilt. I didn't have a misfire before I had it rebuilt but now I do. I replaced ICM ,Coil , Pickup coil ,sparkplugs, sparkplug wires, cap & rotor had it put in time by a shop. It misses worse when the engine gets to normal temp.When I first start it up you can't even notice a miss. And I get a P0300 Random Misfire Detected. Does anyone have any ideas please help me.

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Maybe the fuel injectors

Posted on Mar 30, 2011

  • mclaen Apr 08, 2011

    That's a good point. These did have some finicky injectors and it's not unusual to have one fail or stick shut.


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There's a lot of things, or combination of things, that could be causing the problem but you could have valves that are adjusted just a little to tight which can cause a misfire as the engine warms up. Other things that come to mind are vacuum leaks, fuel pressure regulator leak, or an injector problem. Don't have a silver bullet for you but that's where I'd start my search. Hope this helps and good luck!

Posted on Mar 30, 2011

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