94 K1500 hard to start runs rough to warm

[briang0]

My 94 Silverado 4x4 with a 350 just started acting up. I spent last night plowing and this morning when I went to start it I had to put my foot to the floor to get it running. It was chugging and black smoke came out the exhaust. After about 5 minute of keeping the RPMs up it smoothed out and ran fine. After another 2 hours of running I shut it off and went to start it after about 10 minutes and I got the same thing except it smoothed out in about half the time. I am planning to throw plugs and wires in it tomorrow they are about 2 years old but only have about 3k miles on them. Any ideas?
I looked through the other threads not much about what fixed the issues.

[jdmccright]

I'm gonna guess that your EGR valve is sticking open or the vacuum sensing valve (VSV) that is connected just upstream of the EGR's vacuum line is malfunctioning (mounted to a flat plate forward of the TB on the passenger side, inboard of the valve cover).

The idle air control (IAC) valve could also be sticking...its abt 1-1/4" in diameter, screwed into the passenger side of the TB base just in front of the EGR valve. You'll have to remove it with a big wrench to get to the EGR so might as well clean it, but don't try to compress the valve tip into the body or you can break it.

Another possibility is that you have a dirty, clogged, or stuck injector that is allowing fuel to drip into the throttle body instead of allowing the pressure to dissipate through the fuel line. Noticing a drop in fuel mileage/usage? Smelling gas in the exhaust? Other signs you're running rich.

Hope this helps!