So I have a 2008 Silverado 1500. I had a misfire in cylinder 8 reporting. At that time I replaced the plugs and wires. Still was having the issue so I took the following steps in order- checked the fuel injectors these were fine, did a compression test again fine, checked the rocker arms all fine then finally did a fuel/carb clean on the truck. After that the truck was fine again in fact even gained more power. After a month of driving it maybe putting 500 miles on it the truck started misfiring again. I am so lost to even figure out where to continue. If anyone has any ideas It truly will be appropriated.

 

Likely dirty fuel injectors. # 8 i just the worse for now. Thats why the motor ran good after using gad additive.

 

We switch the fuel injector with cylinder 3 and 8 was still miss firing before the clean was done.

 

Is it still just #8? What does the spark plug look like?

 

Still 8 the plug looks good but cylinder 7 plugs was really bad when I changed it to the point it looked like it was built up carbon. But 8 was and is good.

 

Well, I'd suggest valve seals