Chris Wooten

Hey, new to the forum here and have no idea where to post my question. I am trying to get help with a issue and hopefully someone here can help!

2002 silverado 2500hd 6.0 gas.
When I start my truck and let it sit there and idle for 2 mins or so after starting while idling, it will start missing bad, struggling to run, and the check engine light in the information center will start flashing. But, if I start it and take off and drive immediately it will run and drive fine. With no check engine lights on, I can't check a code. With it getting cold here, I like to go out in the mornings and start the truck and let it warm up and defrost prior to leaving the house but I can't start it and leave it. If I get in it and go, it does fine. But if I start it and walk away, it'll be a bad rough idle and the light will start flashing as the truck shakes and missfires and struggles to run.

Hoping this is a simple fix and someone here can help.

Towerladder300

Definitely get the codes read. Even though the engine light goes out you more than likely have a stored code and I would guess it’s a PO300 random misfire. Have you done plugs on it or plugs and wires?

Chris Wooten

Not yet. From my past experience the light would come on and I would just switch coils out and reset the light. Yes that was the code but im thinking vacuum leak. Would this cause this as well or maybe a intake gasket bad?

Towerladder300

I would say it’s possible if your thinking vacuum leak if you don’t want to just throw parts at it you can make a home made smoke tester, from YouTube search 10$ evap tester it actually works well and smoke the intake see if you have leaks there or in the rest of the system. Can also just spray carb cleaner or something flammable around the intake and if the engine revs up then you probably have a leak.