I agree with foggy you probably need to move on to the electrical side, start by ohm testing the harness coil/injector HARNESS and go from there
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2012 Suburban Misfire #5 drama
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I think you pretty much narrowed it down then. Wiring harness issue to number five coil, or you've lost your oil control ring on piston number five. So yeah, I think you'll need live data to confirm the coil firing normally or abnormally. That's the more likely issue. You don't want to drive it too long with the misfire. Or you'll be looking at a catalytic converter issue next.
Dustin Jackson
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Some good advice in here. I think I comment on your Facebook post but I’m curious on the cam lobes for that cylinder. The LS lifters can fail in different ways even when not AFM lifters. The tray that holds them in position is plastic and the lifters can spin in the tray and damage the cam lobe and wear it down resulting in poor ignition conditions
If it comes down to it you should be able to peak down the valley cover at the cam but let’s start with the basics before opening the motor. I think you’ve tested the spark, compression, and fuel not sure what’s left to check before you dig in
If it comes down to it you should be able to peak down the valley cover at the cam but let’s start with the basics before opening the motor. I think you’ve tested the spark, compression, and fuel not sure what’s left to check before you dig in
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Keiterburb
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Just looked over wiring and checked for power and ground to the main coil pack disconnect, had both there with key on engine off. Shot for continuity from coil #5 connector back to main coil pack connector and all wires were solid there. Also 12V was solid at first injector connector. I did find some wire bundle with wear indication way down under power steering reservoir also looks like it was misrouted during someone’s previous service work.
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Dustin Jackson
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@Keiterburb Mine is routed through the power steering lines like that also I saw a couple weekends ago. Not sure if that’s from factory or not
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Cylinder #5 TDC leak down test only 4% leak rate out rings, could hear only through the oil cap. So other than a borescope in the hole I think I may be down to having to pull everything back off including valley cover to see if I can inspect the Cam lobe for wear?
I would do a noid light test before tearing the engine apart.
for me pulling it apart and not finding anything mechanical wrong would be a last resort. but yeah, a afm delete would at least make it worth while.
when I said check for power, I'd use back probe pins, at the individual connectors on the coils. these are lole 5$ on Amazon and hope there's a lower voltage on #5. you can follow the wires thru the seal and to the pin inside without damaging anything.
you probably don't have it handy, but I'd pull out my pocket scope next and check the trigger wire at the coil from the ecm. but these days mechanical work is the last thing I like to do. if your multi meter does hz. it might tell you something, but not sure.
byond that I'm out of ideas.. back to basics. have you looked at the fuel trims and miss fire counts? when it's missing on a gm the miss fire number will constantly count up while it's missing. that and something as simple as a loose spark plug will miss.
when I said check for power, I'd use back probe pins, at the individual connectors on the coils. these are lole 5$ on Amazon and hope there's a lower voltage on #5. you can follow the wires thru the seal and to the pin inside without damaging anything.
you probably don't have it handy, but I'd pull out my pocket scope next and check the trigger wire at the coil from the ecm. but these days mechanical work is the last thing I like to do. if your multi meter does hz. it might tell you something, but not sure.
byond that I'm out of ideas.. back to basics. have you looked at the fuel trims and miss fire counts? when it's missing on a gm the miss fire number will constantly count up while it's missing. that and something as simple as a loose spark plug will miss.
