Erratic idle at start up on 7.4L Vortec

[dbperformance96]

I have a 1997 K3500 crew cab pick up with the 7.4L Vortec motor. My problem is when the truck is cold and I start it up the idle is erratic, high then low, high then low. This goes on until the truck is warm approxiamtely 160 degrees or so. The truck also has the p0300 code random misfire. I have changed the plugs, wires, cap and rotor, injectors, fuel pressure regulator, and the maf sensor. Do you have any idea what else I should be looking for? After the truck is warm it runs good minus the misfire at idle only. The truck has about 143,000 miles on it. Thanks in advance for any help you can offer.

[454ss]

sounds like the lower intake gaskets to me, thats the way mine acted when the gaskets failed, sort of like the high idle/surging you get with vacuum leaks. is your coolant low or can you see it puddled up around the intake anywhere?

[GM-Tech]

I agree. Sounds like a possible intake leak.

[dbperformance96]

No loss of coolant. I did the lower intake gaskets about 4000 miles ago, because of coolant loss. But don't have that problem now. This one is really bothering me. Hooked it up to the scanner last night, didn't see anything out of the ordinary. Bank 1 sensors were anywhere form 700's to low 60's is this normal. I had a lean code bank 1 on the truck. Could the o2" be causing me this grief? Thanks again for the help.