I have a 94 k1500 5.7 with ignition problems. It skips at idle the tach started jumping around only on idle and when you put it under a load like keeping speed on the interstate the valves start rattling after a few minutes them cylinders start misfiring then the ignition cuts in and off but if you coast it it’s comes back around. New plugs wires new distributor. I don’t know what else to do here can someone please help me as I’m about to just put a hei distributor in it

 

Ignition coil.

 

I’ve changed it too. Distributor plugs wire and coil all brand new. No change at all not even the slightest

 

I'd do a valve adjustment myself. You said you valves are rattling, so try that first.

 

How many miles on your '94? Was this a sudden problem when it started or is it getting gradually worse?

 

it was a sudden problem. The truck has 238,000 miles the engine has 78,500 miles on it according to the paperwork that I have the valves start rattling like when you’re going up a hill a steep hill are pulling a trailer putting it under a load over here or something and you’re on it for a minute they start rattling you like it has too much ignition timing then it starts skipping and it starts with one cylinder and then a couple more then it’s like you’re cutting the ignition on and off but if you let off the gas for five seconds to coast it it comes back and it’s fine