2000 SILERADO 1/2TON 5.3When starting the truck, it will fire immediately but it's barely running, VERY ROUGH on 5-6 cylinders. If I give it throttle, it'll smooth out and give no more problems. If I don't give it throttle it usually dies. If I let it die, Ihave to crank it 3X longer than normal to restart it. This usually happens on first start of the day, but also if I drive somewhere and shut it down for an hour or more. There are NO TROUBLE LIGHTS, NO OTHER SYMPTOMS at highway or city traffic speeds, it still seems to have all the power and response it ever had. Has anyone seen something like this???

 

I had the same problem with my 2000 sierra with a 4.3. I chased this problem for like a year changing a lot of ignition pars and it turned out the fuel pump was going bad. i replaced the fuel pump..............no more problems

 

You're fuel pressure regulator is leaking gas in to the vaccum line. Turn you're key on then unplug vac line off of regulator. If raw gas comes out replace regulator. That is a very common problem.

 

Dirty Dave Thanks, I pulled the vacuum line and bingo gas poured out. I'm picking one up tomorrow.
$48? Yikes, but it sure beats a fuel pump.