GM HEI trouble update

NKau

Founding Member
Dec 15, 2001
1,346
0
37
Jefferson, WI
Well, the ignition problems in my truck ('86 chevy silverado, 305) have gotten quite a bit worse. Now, upon startup, the truck will run OK while in cold idle, but has an audbile miss. After the truck warms up, the engine will not stay running if partial throttle isn't applied. It will miss progressively worse as you lean out of the gas, and flat cut out once you get off it; conversely it seems to run just fine at higher rpms, or under load when you lean into the gas. Supposedly symptoms of a bad HEI module indicate that you should be having problems at higher rpm/under load; opposite of what I have going on with mine. It's done this on occassion in the past, but not to the extreme that it can't idle on it's own. I'm kind of lost here..........
 
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Only time I had problems with missing on my old F-body (HEI) was due to a bad plug wire. It was new out of the box MSD and caused a serious miss.

Another issue I had was a poor 12V connection the HEI coil which led to random no start issues.