1977 Chevy LUV

When driving at about 60-65 mph, My 1.8 liter engine has a random miss. It jerks and stammers like it is an electrical problem. The miss is only one to three seconds in duration then it quits. Come one minute to twenty minutes and it misses again–like pop pop pop then clears up. I’ve installed a new distributor, new wires and ‘ohmed’ out the coil and ballast resistor–they check out OK. Now the real problem is when I turn on the headlights, the miss goes away completely. I have even isolated the electrical circuit by running a new switched wire from the battery to the coil. The only thing left of the orginal wiring in this case is the resistor by-pass wire but I had it disconnected too–for a while–still misses. So I’ve reconnected it. I checked the voltage at the coil and it was 15.2VDC, a little high. I put in a new voltage regulator. Still misses–except when I turn on the lights. By the impact of the miss, it just doesn’t feel like it is a fuel problem. Plugs and wires are new. Coil is not new but checks out according to the Chevrolet LUV repair manual. Anyone have any ideas?? Thanks for your answers. Don

high speed misses are almost always ignition/electrical in nature.check your plugs.air filter,pvc,vacuum lines good as well?

I would run a good ground wire from battery to engine and motor.
Easy and cheap, alot of older cars have weak connections

sounds like carb issues to me,dirt,cruise circuit,accel circuit,ect.

I’m kind of inclined to agree that it’s a carburetor problem and the headlight thing could just be coincidence since you’ve run a hot wire directly to the coil.

Another possibility could be an ignition condenser getting the hiccups but I assume a new distributor was loaded with a new set of points and new condenser.
And I’ll also point out that a ohmmeter is not always the final answer when testing an ignition coil, or even a plug wire.
It may show fine at that particular moment when tested but when heating up a bit may start breaking down.

Does this thing still have points? If so I’d change those out along with the condenser and set the dwell, preferably with a dwell meter. I’d also check the voltage at the other side of the ballast resister to make sure it’s actually working right. The voltage should be about half of battery voltage. Ballast resisters are one of those stupid little electrical parts that the build quality seems to be really poor on from most parts sources these days. Condensers are another one-- I used to go through a couple of them before finding one that actually worked properly and didn’t toast the points too fast.