Just acquired a 2011 Silverado with the 5.3 at a gov't surplus auction. It has about 150k miles, was 2 qts low on oil, and is throwing P0304 (misfire on cylinder 4) and P0455 (evap large leak). I'm going to try plugs, wires, a new coil, and a gas cap as the first attempt to solve this.
Internets lead me to believe it may well be AFM issues. If it ends up as AFM, I will probably go the delete route. Any good sites to look at for AFM delete info, kits, etc.? Looks like I would need a tuner if I choose to delete and a quick glance shows several "versions" or whatever they are called of HP Tuners. How do I decipher which one is the one I'll need or want?
Any good advice or recommendations on guides, parts, etc. is appreciated.
Large evap leak is PROBABLY the vent solenoid. It's a persistent issue. I have also seen purge solenoids stick open and cause a '455 without managing to set a P... I forget what, incorrect purge flow.
If the cylinder 4 misfire is due to an AFM failure, you're going to be replacing the lifters at a minimum. To do a "proper" delete you need to replace the lifters with non-AFM lifters, and a non-AFM cam, since the lobes are different. The software is easy, you just get HPTuners and uncheck a radio button in the tune.
Anyone with gm hptuners can plug in and for $100 in tuning credits write out the afm and associated codes with a few clicks and a reflash.
as I understand it it's lifters, trays, cam, and valley cover. The problem is it's a heads off job. We weren't lucky enough to know about the problems until rod knock came at 118k and instead of finding another afm engine I picked up a 2010 4.8(no afm) and tossed it in and reflashed the pcm to delete the afm demands and codes and all was right with the world
