My 93 Chevy Suburban has a baffling case of the hiccups. This is 3/4 ton 4X4 truck with 350 v8 and a throttle body carb. At speeds below 65 the engine purrs and runs great. When I hit 65 mph the engine produces an occassional stutter or hiccup. I have installed new plugs, plug wires, distributor cap and rotor. This seems to have lessened the frequency of hiccups but they still occur. There also seems to be a random quality to this phenomenon. No rhythm or pattern is apparent? Any ideas on this?
Perhaps a weak fuel pump? Worn distributor?
When there are doubts about ignition I always check the #5 and #7 ignition wires and make sure that they go to the right cylinder and keep them away from each other because crossfires can happen. When the spark from 5 goes to 7 it will cause preignition.