I have a 2015 6.2 (L86) engine that had a stuck #7 intake lifter. I was able to unstick the lifter using the special tool, but now I have a small miss that counts up only at idle on #7. Fuel trims are negative, but very low and are both very close to each other at all rpms EXCEPT idle. At idle Bank1 is skewed negative by 7 points (LTFT1: -10 vs LTFT2: -3). I replaced that injector and made no change. All the injector seals were intact. NOTE: Misfires only count up on #7 at idle or at extremely low rpms. It never sets any misfire codes, but you can feel the roughness in the steering wheel and it doesn't idle cleanly. It does set fuel trim imbalance codes. Sometimes just bank 1, sometimes both banks; i.e. P219a/P219b. I checked compression and #7 had 230psi & #5 had 260psi. I put a couple of squirts of oil into cylinder #7 and the reading went up to 260psi which would point towards a ring issue. I was leaning towards a damaged camshaft issue, but am having hell trying to get my dial indicator setup to work (brake booster in the way) so I can't 100% verify the lift vs a k/g cylinder. For what its worth, I didn't see the dial indicator needle jump when checking the lift over the nose of the cam (which might indicate damage). Lift reading was questionable though as mentioned due to the booster. Maybe the lifter or rocker arm (bearings) are damaged and have some play in it or something weird like that but I would expect misfires at all rpms......? Maybe not....? The low compression seems to point to a camshaft problem (truck was great before), but the compression jumping up with the oil test has me perplexed.......Appreciate any thoughts/suggestions before I dive into this pos ;-) Thank you.
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Editada: 14 dic 2021
Anyone have misfires after unsticking an AFM style lifter?
Anyone have misfires after unsticking an AFM style lifter?
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Ahh, yes it's direct injection. You should be able to get at master injection harness back of engine. Worst case find diagrams and take the ground pin out of master connection for the #7 injector. That will be very tough though. I suppose one could do the ECM pin, that would be easier.
Thank you. I wanted to do a running compression test, but I can't get to the injector connector.....I'm wondering if I can disable that injector in HP Tuners temporarily to run this test.....? That would really help figure this out. Either way, this is good and will help --- thank you again!
Don't dwell too long on the oil adding compression. If it is misfiring and the rings get washed by the unburnt fuel, oil will make it gain compression. Also adding oil if too much will shrink the chamber volume raising the compression on the gauge. Something else worth noting, a compression test the conventional way won't show you a low lift from bad lobe condition. It also won't show a small valve leak. To see these you need running compression and cylinder leak down test. The running compression is when you run the engine with injector unplugged while purging the gauge and watching how fast it builds to x pressure. Then compare to a good cylinder. This is great for identifying low lift or stuck open valves. To verify whether or not it's a valve leak you will need a cylinder leak down test. This of course identifies where it's leaking if it's leaking. If you have little running compression but no cylinder leak down then it is a worn cam lobe. This will help you get around needing to get the dial indicator on there.