Odd Random Misfire On 2000 Silveradod 1500 5.3l

[Beebe]

My check engine light went on, so I went to a friend who has a scanner. We scanned it and found a random misfire code. We cleared it and it comes right back. His scanner is capable of showing data from the engine like misfires, rpms, etc. So we tried that. Well I'm getting misfires all over the place. Not just one or two cylinders, but all of them. I replaced plugs and wires at 100,000 miles, and know have 145,000. The wierdest thing is it only misfires at idle. I took the truck for a ride with the scanner and had ZERO misfires in about 10miles. The instant I stopped the misfires start.

Does anyone have an idea as to what is going on? Help would be greatly appreciated.

Thanks

[Beebe]

Anybody?

[98 Z71 SLT]

Intake gaskets.

 

If those are ok, fuel pressure regulator

[TexasAl]

Do these trucks come with an Idle Air Control (IAC valve)? If so, I'd take a look at that.