I bought a used 2008 Silverado LS 4WD last year. Unfortunately it is just past warranty (5 years old) and my check engine light came on. The code is for a Cylinder 8 misfire, which seems like a relatively common problem and I assumed it would just be a spark plug or coil pack change.

I dropped the truck off this morning at the dealership and they said after running diagnostic tests that they know it is NOT the plug, the coil, or whatever they would have found by removing a valve cover? The only option left was to actually take a look inside the engine which would involve 19 hours of labor, estimated at $1,700.

They could not guarantee that this would give them a clear answer as to what was causing the problem, so for now I told them not to do anything with it. I cannot afford to drop $1.7k on a POSSIBLE solution. I thought I'd check with folks here first to see if they might have any ideas on what could cause the issue and if this is an issue that necessarily needs fixed. The check engine light seems to come and go intermittently and has been doing so for the past 3 weeks.

Thanks in advance for the help!

Anthony
-2008 Chevy Silverado 56,000 miles
-4WD
-Engine Size 4.8L V8
-Crew Cab

 

Plug, wire ,coil pack, or injector would be the easy things. Check the compression on that cylinder and see if is low. Then go from there

 

I have a few chevies that misfire on random cylinders. I stopped taking the truck to the dealership after I got same money robbing proposal. The common thing I have noticed is they both only throw misfire code while idling for 5 minutes or more. My mother is borrowing one of the trucks today and I expect it to have this code stored, cause she sits in car yacking on phone idling in driveways ect. talking with clients. Hope this helps.

 

Sounds to me like you are dealing with a crook.

A simple compression test will tell you the story. No need for disassembly.

I always like to know exactly what is wrong before ever picking up a wrench.

Allan

 

It turns out it actually was the cam. One of the lobes on the #8 wasn't smooth like it should have been, it was abrasive, like a nail file, at the top where it hit the pin.

GM is doing right by me though, car is 5 weeks out of warranty with 56k miles and they are going to cover the cost of the cam replacement, and whatever is ailing the transmission since it doesn't seem to engage 2nd gear (even if it needs replaced) as long as I pay $500.