2012 Suburban Misfire #5 drama

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hagar

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On the off chance that the crankshaft position sensor or the cam position sensor have been replaced or could otherwise be suspect (or not), do a CASE relearn just to rule it out.
That is a great suggestion. I looked at a buddies 6 liter with high miles a few years back that was misfiring, though his was on a few cylinders, and couldn't find anything wrong with it. Did a crank re learn and it smoothed it right out and ran great until it got stolen a few months ago. In his case I think the timing chain was getting so much slack from the mileage, it was throwing off the cam to crank timing. Couldn't hurt to try.
 

2015TahoePPV

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my 2010 had a strangely similar issue once, I'd circle back to that bundle of wires near the power steering pump. I've seen a few threads out there on the internet about those wires rubbing through and shorting, and the weird nature of this one feels very similar. Your P219A could also be indicative of an issue with that side's injector's harness. I'd get the pin outs to the ECM and ohm the connector from the injector harness to the ECM and with your meter connected I'm betting you will see the issue if you jiggle that harness by the power steering pump.
 
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bazec

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i had a situation with #4 misfire after much head scratching found no crank compression good. Running compression low #4 V-lom
leak by killing #4 lifters. Changed V-Lom no more problems
 

bazec

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i had a situation with #4 misfire after much head scratching found no crank compression good. Running compression low #4 V-lom
leak by killing #4 lifters. Changed V-Lom no more problems
2014 Tahoe 5.3
 

Rush1

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Try a crank position sensor relearn , That usually takes care of a phantom cylinder miss
 

West 1

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Compression was good so I would certainly start with a scan tool that can shut down the injectors one at a time and see if the power balance is normal. The injector in 5 might be getting bad signals from the computer. I believe they only open when supplied a ground circuit so maybe the injector wire is shorted to ground somewhere hanging the injector open? Your fuel trims are trying to pull fuel out of bank 1 so extra fuel is getting there from somewhere. It is either no spark not burning the fuel or extra fuel dumping in from the injector in #5.
 

solli5pack

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Definitely going to need a scanner that shows live data otherwise all your doing is taking guesses. Even though you're getting a P0305 you can't even be sure the cyl 5 is the issue without verification using a scanner.
 

j91z28d1

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well #5 did have carbon on the plug and running rich.

but if you could graph o2 voltage to confirm. that would be handy. here's what a high ohm injector looked like on my ls3 car. no miss or any signs till I happened to see the o2 volt on in a log and started investigating. purple is the saw tooth miss fire, light blue is normal side. it's zoomed in very tight time was in this pic. about 1.5sec full screen width

Img_2025_03_17_18_49_38.jpeg
 

solli5pack

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well #5 did have carbon on the plug and running rich.

but if you could graph o2 voltage to confirm. that would be handy. here's what a high ohm injector looked like on my ls3 car. no miss or any signs till I happened to see the o2 volt on in a log and started investigating. purple is the saw tooth miss fire, light blue is normal side. it's zoomed in very tight time was in this pic. about 1.5sec full screen width

View attachment 452756
Is that a scanner with an oscilloscope feature?
 

j91z28d1

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Is that a scanner with an oscilloscope feature?


hptuners scanner side. it's pretty good for surff like that. they have something to make the update rate much faster than normal scanners. which is needed for capturing fuel trim data to tune off. but side effect is you can log tons of stuff really nicely.

there was a time you could buy just the scanner side. but I don't think so anymore.
 

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