Jeff Curry

ok I took the 2008 5.3L avalanche to tennessee from kentucky a about a month ago.all was fine, there and back, the truck sat about a week, when i started it back up after a week it was missing. so i knew it had been a few years since it had spark plugs in it, so I got new plugsfor it, granted its a 2008 with only 35,000 miles it is not a daily driver. still missing, plug it to 2 different computers showing misfire on cyl4, so i try a new coil, even switch coils and wire from cyl 2 and 4, still shows misfire cyl 4. pulled the plug wire off as its running, coilk is arching fire, pulled out the plug laid it against the motor cranked it over, plug is firing still. thought the fuel injector was stuck open (since the plug had gas on it) so switched injectors from 2 and 4 . still shows cyl4 misfire after clearing the computer. must mention the inner fender from the pass side is gone, the same side that cyl4 is on, and it rained all the way back from Tenn, so water was getting up in the motor some. but all wires check out, with fire and fuel, did a compression check on cyl 4 and 2 to see the diff, thinking it might be a cam lobe wore off or even a valve stuck. compression on cyl 4 was arond 130 on cyl2 was around 150, so not alot of diff.A friend said on the 2008 models they installed a "charcoal Box" tha has wires and vacuum hoses, that his uncle has a 2008 silverado with the 5.3L motor and it was showing misfire but was quitting all together, said it controls the fuel pump. would this make a misfire only on one cyl it it got wet???
I dont know what else to try, there is no clenging or noise in the motor/heads etc.. to think it is a valve stuck or burned or any black smoke from the exhast.....wha else can cause this i doibt kniw what else to try and the chevrolet garage charges 100 to check and 100 per hour to work on it..

thanks
jeff

Jeff Curry

I also forgot to mention, yes the service stabilink and service traction control light message stay on. About 6 months ago they had to replace a oil pump, and the truck only has 35,000 miles and its an 2008, its hardly ever driven just one or twice anm month... when they replaced the oil pump, they also said all the fuel or 02 SENSORS were bad cause it was taking so much gas to go very little disstance, amd they suppossedly service both the stabilink and traction control. i called them after the service light started coming back on and they said they only replaced one of the traction control modules or whatever it was and another one must of went out. We usually run the truck in AUTO 4WD in case it needs to kick in especially in the winter here in Kentucky. seems like the last time i tried t get itin 4L to come up my muddy driveway without spinning it would not go in at all......would the stabilink and traction or thrittle body make a cyl misfire? I saw another post of someone here sayong when the traction control service light comes on theirs misfire on cyl 6...pleawe helkp this truck had had some much money spoent on it already and has low low miles for the year its was made, and its rarely driven.....