Electrical miss

96 GMC 1/2ton PU, 4.3 V6 Vortec.115,000 miles now. Great truck. All maint. performed regularly. At 100,000 miles I put all new lifetime plugwires, Dist. cap, rotor, and new bosch plugs in. All OK for 6 months. NOW, on startup after sitting a day or two, it misses real bad for 15 minutes or so and then goes away. Let it sit 3 to 4 hours, start up and it’s still good. Let sit all night (even with no rain or 70 degrees and dry all nite) darn thing misses. Seems to be worse at lower speeds. I’m baffled.

I assume the check engine light isn’t turning on but if it is then you need to check the codes. It would be nice to know if all the cylinders are missing or if it is just one. There may be a problem with the coolant temp sensor since the trouble clears after warm up. I would start with checking that out.

I would get rid of the Bosch plugs (I’d had the same problem with them causing misfires), and look real closely at the aftermarket plug wire set. Most aren’t very good. I’d put OEM wires on.

I put all new lifetime plugwires, Dist. cap, rotor, and new bosch plugs in.

I would go with OEM parts. My experience indicates that those fancy expensive ignition parts are all show and no go. Save your money for something else and use OEM parts.

Thanx guys. I visited my local autoparts dealer where I purchased plugs etc., and was told the plugs were crap. Go with AC Delco (OEM) and switch out the wires for a new set. And yea, it was throwin a code. Electrical miss. DUH!! Goin out now to work on it . (Cooled down now)

I wouldn’t ignore the spark at all - but I would actually be looking just as much, if not more, at fuel delivery. Change fuel filter if its even close to being due. Put a fuel pressure gauge on it - leave the gauge on for a while and watch what is happening over night, when you restart it, etc.