Hello. I am new here. My 97 K2500 has had the normal problems since buying it a year ago. A new mystery has me troubled and I need some suggestions. First, some background. Engine was changed with all the old stuff put on it. I have replaced the wires, distributor cap, spider and the regular filters, plugs etc. When I first got the truck, it had a barely noticeable irregular miss at a constant driving speed. That has turned into a very bad jerking, surging situation with the occasional pop from the exhaust. It idles fine with a slight mis. It accelerates fine with no apparent problems. At any constant speed, very bad! Un-drivable. To go from point A to point B I must go fast then coast. Please help.

 

Found it! When I was about to adjust the timing as a last ditch effort, I found the distributor was loose and had turned. Perfect again after fine tuning!!