I replaced an ignition resistor wire that I was running to my HEI this past weekend, but it did not solve the misfiring problem. Us guys with the older points style ignition who convert to HEI are supposed to replace the factory ignition pimary voltage wire to the coil with a 12gauge wire. I neglected to do that originally and thought that my idle misfire was a result of that. Apparently not.

I asking a few of my buddies if they know anyone with a good shop that has a scope. But what would it tell me if someone was to do it?

I've verified all engine internals are good (cam, heads, lifters, pushrods, etc.), sensors, plugs, wires, cap, coil, rotor, distributor, injectors, wiring harness, ECM, PROM chip, vaccum lines, fuel pump and filter, pressure regulator. How could this freakin' thing still be misfiring?? There are no trouble codes. The only indication that something is wrong is a really noticeable misfire at idle speeds and a bad stumble anywhere below 2500 rpm. I've also spent an inordinate amount of time with my new CATS Real Time Tuner trying to "tune" the problem out, but to no avail.

 

You might try swapping the distributor for a known good one(or just the pick-up coil), I had a kind similar problem with stalling at idle speed, and after changing every part except for the pick-up coil, thats what it turned out to be, either a weak pick-up coil, or corroded connectors to the pick-up. Cured the stalling/roughness. Its also possible that spark plugs could cause problems. I've seen champion plugs work terribly in Chevy motors, don't ask me why. Try a set of good ol AC delco R45TS plugs(if you haven't already). Just a couple things to try. Hope that helps. And just to double check, the spark plug wires are OK, no burns, bad crimps, etc?

 

i've seen some GM roller lifters cause a problem like yours...miss at idle and stumble off idle...ran ok WOT

 

Yeah, acutally the distributor is a brand new unit from Davis Unified Ignition. I bought it in an attempt to solve this misfiring problem. I've tried several different sets of wires and plugs, but nothing works any differently. I'm completely stumped.

 

I've also swapped out the lifters for some new ones from GM. Supposedly some "new" design. However, the new ones were a little noisier and didn't solve the misfire. So when I changed my cam, I put the old lifters back in.

 

lean miss fire maybe....all injectors opening ok?is it a dead miss that you can feel makes the car shudder or more like something you can feel in the car shaking? also any backfiring or noise out the exhaust?check the wiring to the module,ESC, and ECM is not picking up inductive interference from the ignition wiring or other surrounding wiring....i know its digging deep but sometimes its the weirdest dam thing cause alot FUBAR