Dropped A Cylinder. Help

uh6077 · July 15, 2007

99 NBS Silverado 5.3 with 123,000 miles. Went to drive the truck today and it was idleing very rough. I drove it a bit to see if it would clear up but it did not. Check Engine light came on after about 2 miles of driving. I came home and checked it out. I felt the manifold and could tell that one was not near as hot as the others. It is the back plug on the drivers side, not sure what number it is. I pulled the plug wire and the idle did not drop at all. I pulled the plug and switched it with one of the good cylinders the problem is still there. So right now it is only running on 7 cylinders. I put a spark plug light on it (between plug and wire) and it is getting good spark. I can only assume it is not getting fuel. Bad injector? Stuck valve? I have not checked compression yet but will later if I need to. What should I check next? Should I pull the codes? If so how do you check the codes? Thanks

GMTRUCKTECH · July 17, 2007

99 NBS Silverado 5.3 with 123,000 miles. Went to drive the truck today and it was idleing very rough. I drove it a bit to see if it would clear up but it did not. Check Engine light came on after about 2 miles of driving. I came home and checked it out. I felt the manifold and could tell that one was not near as hot as the others. It is the back plug on the drivers side, not sure what number it is. I pulled the plug wire and the idle did not drop at all. I pulled the plug and switched it with one of the good cylinders the problem is still there. So right now it is only running on 7 cylinders. I put a spark plug light on it (between plug and wire) and it is getting good spark. I can only assume it is not getting fuel. Bad injector? Stuck valve? I have not checked compression yet but will later if I need to. What should I check next? Should I pull the codes? If so how do you check the codes? Thanks

If you can get a scaner to make sure it is a P0300 misfire code and find out what cyn it is that would help. If not you could do the feel on the exhaust but that must hurt! You could try pulling the igniton wire of each coil one a time to see if there is a change in the way the motor runs. If you pull a plug and nothing changes then that is your troubled cyn beware though you will get shocked! More then likey its a injector spraying to much fuel or to little. There is a gm injector flushing procedure but you need special j-tools to do it. If I was you I would get your injectors flushed first and think about doing a tune up with that many miles. It's highly unlikely that you have a compression problem with a 5.3. Good Luck

sagent · July 17, 2007

This happens to my 02 Sierra all the time. Usually with a few taps of a screwdriver handle on the plugged injector & a few cans of injector cleaner in the tank it will begin flowing fuel again.