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I had trouble with a hard cold start and rough idle.My old mechanic retired and went to another recommended by a friend. He did a carb kit rebuild and it improved the situation. It still had a little rough idle but he advised that with a Holley 4180C carb you should warm the engine before driving. (I have never heard of that before). I drove it home on the county road with no trouble but at low speed. Did not drive for about 2 weeks and took it out on the main highway. Accelerating to highway speed when it reached about 30MPH it began to cut out -run-backfire-cut out-run-backfire etc. When below 30 it was OK. Repeat acceleration and began cut out and backfire about 30. I am no expert but it sounds like electrical involving either the ECM or the module in the distributor. Any thoughts?
Rollie, Rollie, Rollie, it would help us help you if we knew what you had, year / motor / any mods done to the truck it would be nice.
It does sound like a spark cutting in and out at a certain RPM.
Now you say ECM or module in the distributor but you have a carb so I dont know what you got or taking of
The ECM in my book is a computer for EFI where the module is for spark.
I think I would give the module in the distributor a try first.
But before that maybe check the connections to the coil. Pull it off and see if it is clean.
Dave ----
Pull the distributor cap off and see what it looks like inside. Check the rotor also. Grab the rotor and see how much play is in it side to side (bearing in the dist shaft). There is the rare occurance where the wires leading to the pickup inside the distributor are broken. The plate that the pickup is mounted moves continuously as the engine is running and the timing is adjusted. These are special wires like meter lead wires and are made to withstand this movement, but when these trucks get old they can fail.