Miss At Idle

[mdwilf]

I have an odd miss at idle - it runs fine when the engine is cold or cool, but once it warms up it has a miss that sounds more like "thunka thunka" than just a dead spot. No knocking, etc. It almost sounds like a plug wire crossed, but I've checked them several times. I've also made the idle richer with no change. The longer it runs, the worse it gets, until you can feel the truck shake a little at idle. Runs great going down the road.

Stock 350, 70,000 miles, HEI, new cap, plugs, wires, rotor, 10 gauge wire from fuse box to dizzy, timing set to low 30s at full advance.

Thanks