So I bought the truck with a bad missfire and drove it home. Got home opened the valve cover and rocker arm was just laying there. So I put all new rockers and lifters in it as well as plugs after that ran great. Till come this winter it started to miss and throw a po300 code and only once a po304 cylinder 4 missfire. I’ve tried a coil pack and new plug in cylinder 4 and it didn’t help. Any ideas maybe a bad or dieing sensor of some kind. But it only misses when at idle in cold weather any help I’d appreciated