I have 1999 Chevy K 2500. According to the scan tool it misfires on cylinders 1 & 4 mostly but sometimes others as well. When driving it, once you hit 40-45 all of a sudden the cylinders pick up and runs like a champ. But then occasionally when I go to stop and then go again the problem repeats itself. So far I have replaced plugs and wires, distributor and the fuel pressure regulator on it. Any help would be greatly appreciated. Thanks

 

What did the plugs look like when you replaced them/
When you say you replaced the distributor did you replace the whole thing or the cap? If not look at the rotor.

 

The plugs and wires looked normal. I replaced the whole distributor cap and rotor so I dont think that would be it

 

Does that have a distributor or coils? If it has coils that could be your porblem.

 

What brand of distributor cap and rotor did You use. Get a premmium ( racing ) cap and rotor and replace the Electronic control module located at the base of the distributor ( use a Delco Remy ). Another thing is to park Your truck where it's cpmpletely dark and with the hood open watch for spark jumping ( with the engine running of course ). I've seen plenty of wire sets do this even if they're new. I've alse encountered problems with the magnetic pickup in the distributor.