dbrieler

I found the problem with my #3 misfire, it was a broken valve spring! I could not visually see it until I had the head rebuilt. This was a real head-scratcher! I put it all back together and the truck runs great. The local machine shop said that it is is rare for a spring to break on a 5.3.

Did you ever resolve this issue? I have a similar problem on #3 cylinder that has me stumped. I swapped injector, coil, wire and plug, code still on #3. Good compression, running test and cranking test** Good cyl leak down Check spark, ok Noid test OK Good fuel pressure 58psi #3 is a non AFM cylinder All valves are actuating, measured travel at approx. .300" intake and exh. cleaned all injectors, #3 had noticeable contamination two different times (even after cleaning and running a few miles) Injector resistance (ohms) is good on all injectors I am beginning to think it is bad fuel due to finding the #3 injector dirty after through internal cleaning but why would it only be on one cylinder? Also why doesn't it clear after cleaning? I first did a running compression test; #3 came up to approx 130-150PSI after I clear it went to zero and would not build any pressure after that. Any time I retry this it has compression at start up but then goes to zero after clearing the gauge. Other cylinders do not do this. Ran a cranking speed compression test with all plugs removed, this cylinder is one of the two best @185psi. This made think a lifter was collapsing after the oil pressure came up so I removed the valve cover and ran the engine, all lifters appear to be working properly.