Kind of a strange one to me. I inherited a low mileage truck, a '99 silverado, long story short gapped all the plugs for farts nd laughter, and now I have an intermittant misfire. Only adjusted the gap on 2, the one was mashed, had a gap of about 10 thou, the other was was .40, which i gapped up to .60 to match the rest, all except the .40 are original from factory. What really throws me, is the truck will not throw a misfire code. Can literally run it with a wire off and it wont throw a code, makes trying to find the bad one a pain. Any advice? Dont want to buy a bunch of new plugs if I dont have to.
Misfire only occurs low speed high load.