2012 Suburban Misfire #5 drama

[Doubeleive]

Yes, can you still rent those at auto parts stores?

Maybe the kit is only $25-30 probably can get one at harbor freight

 

[Fless]

I agree that more tests are needed before tearing down. In addition to the noid light test, I'd probably borescope that hole and turn the engine over by hand to verify that both valves are opening and closing fully, and nothing looks off (like very clean head and valves combustion side surfaces).

Also, an injector balance test might be worthwhile.

 

[Keiterburb]

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.

Thanks for the suggestions; I have been shooting power with disconnected connectors but will check for needle probes around my garage or order a set to test while running. Also, ordered noid light test kit as I am was out in Wyoming and part stores have no loaner tools.

I have an Innova 5610 and have watched the live data but unfortunately no live misfire counter. It was pulling fuel from bank 1 while running. Would love to get a great scan tool one day but can never decide on one.

 

[Keiterburb]

Maybe the kit is only $25-30 probably can get one at harbor freight

Placed on order, will take a few days to arrive

 

[Keiterburb]

I agree that more tests are needed before tearing down. In addition to the noid light test, I'd probably borescope that hole and turn the engine over by hand to verify that both valves are opening and closing fully, and nothing looks off (like very clean head and valves combustion side surfaces).

Also, an injector balance test might be worthwhile.

I have a borescope on my desk at work, I'll bring it home tomorrow while the plug is still out from leak down check today.

 

[j91z28d1]

huh so it has a miss fire fault code and feels like it's missing at idle but you're not seeing the miss fire numbers climb.

I'm not sure what that means, but it's not what I've seen happening on my stuff.

you have a very interesting one.

 

[Keiterburb]

huh so it has a miss fire fault code and feels like it's missing at idle but you're not seeing the miss fire numbers climb.

I'm not sure what that means, but it's not what I've seen happening on my stuff.

you have a very interesting one.

Not exactly, I have no misfire counters on my ******** live data so I don’t know. Just know it has a miss and code returns

 

[rdezs]

I'm thinking you're not getting a code for misfire because it might not be misfiring..... As far as the coil and spark plug go. But I would definitely want to confirm that with live data while it's running at different RPM, and completely rule out the electronics including the ECM.

Having passed a leak down and compression test, and only happening on one cylinder..... I'm leaning toward it's one of the lifters acting up. I'm wondering if the fouling of the spark plug is due to either the exhaust valve not opening all the way and that cylinder can't push all the exhaust out, or the intake valve not opening all the way, not allowing enough air, which also would foul the spark plug. Above vital with more oil pressure, I can see the lifter functioning properly.

How is your oil pressure by the way?

 

[Keiterburb]

I'm thinking you're not getting a code for misfire because it might not be misfiring..... As far as the coil and spark plug go. But I would definitely want to confirm that with live data while it's running at different RPM, and completely rule out the electronics including the ECM.

Having passed a leak down and compression test, and only happening on one cylinder..... I'm leaning toward it's one of the lifters acting up. I'm wondering if the fouling of the spark plug is due to either the exhaust valve not opening all the way and that cylinder can't push all the exhaust out, or the intake valve not opening all the way, not allowing enough air, which also would foul the spark plug. Above vital with more oil pressure, I can see the lifter functioning properly.

How is your oil pressure by the way?

Definitely a miss at idle with small engine shake and P0305. Oil Pressure is always good. Changed sending unit about 18 months back. Checking remaining diag options without a 2-4K scan tool before inspection of cam/lifter

 

[Fless]

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.

 

[hagar]

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]

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.

 

[bazec]

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]

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]

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

 

[West 1]

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]

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]

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

 

[solli5pack]

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]

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.