I have an 09 Sierra CrewCab (5.3L) with 71,000 miles on it. The check engine light came on and I limped into the dealership. They ran a diagnostic on it and it came back that cylinder #6 was misfiring. They ran checks on it -- replaced plugs and wires and still misfiring. So they are now going to replace all the lifters and the cam in the truck. Does this make sense? Something is not sounding right to me...but I am not a mechanic.

 

Well keep in mind there are only three things needed for proper ignition. Spark, fuel and compression. Sounds like they've ruled out the spark portion, and I'll bet that the fuel isn't the issue. So unless they've ran a compression check ... or better yet, a leak down test to see WHERE you're loosing compression from ...

Basically, they could be on the right track, but I always prefer to narrow it down even further. Low compression WILL cause a misfire, but I think that they should evaluate the condition of the engine. For example, if your rings are shot, then a new engine is in your future ... if your valves are leaking, then rebuilding the head might be in order. Just throwing a cam and lifters at it could very possibly fix your problem though. It's up to you how much you want to trust them.

But personally, I wouldnt let them do it. Get a second opinion, or have them prove to you that the camshaft is the issue.

 

Worn cam lobe no valve opening? Seen a few.

 

The AFM (Active Fuel Management) lifter on cylinder 6 collapsed so they replaced all 4 of the AFM lifters and the cam. Compression is good across all 8 cylinders (159 - 161). I have another question for the group: what is the normal oil pressure range for an 09 Sierra with a 5.3 with AFM with 71,000 miles on the motor? At idle, mine is about 18 - 20 and if I really goose it and lay on the gas, it will get up to 40. Normal hwy cruising at 65 - 70, it hovers around 25 - 30. Is this normal? My low oil pressure warning light has never come on and the dealership I take it to says that oil pressure is normal.

 

If a new cam was installed should have had all new lifters. Under the oil pressure sensor is a screen to block debris from getting into the valve plate for the lifters. If this screen gets debris oil pressure reading will be low as the sensor is above it. Partially plugged? Usually message for low oil pressure will come on if plugged.

 

Quick update: All 4 AFM lifters were replaced and a new oil pump was installed (all under warranty). Compression is good across all 8 cyliners and all looks good. Thanks for the all the input...

 

I have a 2008 Silverado 4.8. At 19,000 miles cam and lifters had to be changed. Lost compression on number 4 cylinder. Things are not built like they use to be...

 

That sounds pretty normal for the oil pressure deal.