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2005 Silverado 3500 6.0

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21 Nov 2019 20:22 #35193 by Cheryl
2005 Silverado 3500 6.0 was created by Cheryl
I’m thinking possibly a crank sensor issue. P0300 see #1 plug wire arcing on exhaust. Put new plug wires and plugs on runs good at idle. The misfire counter is acting funny. I’ll unplug cyl 2 coil and it’ll count on cyl 2 and 7. Those are the 2 cylinders that count up on a load. Swapped coils. Flow tested injectors all the same. Performed crank relearn. Out of ideas. Vacuum gauge nice and steady even when misfiring. Had to diagnose a no communication with any module before to even look at live data has a rotted airbag module. Unplug 1 cylinder to test the accuracy of the counter it’ll always be in accurate. Any ideas??

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23 Nov 2019 09:08 #35232 by Tyler
Replied by Tyler on topic 2005 Silverado 3500 6.0
Maybe use an amp clamp on the coil fuses with an ignition sync to see if timing is changing on #2 or #7 when the miss is occuring? One coil getting fielded too little/too much or just flat not occuring should stand out like a sore thumb. :cheer:

It just so happens I ran into my first failed 6.0L crank sensor last week. :lol: Tach wouldn't operate most of the time, long crank. Green is the CMP, yellow is the CKP. There should have been 58 teeth in the CKP waveform...

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23 Nov 2019 10:05 #35235 by Cheryl
Replied by Cheryl on topic 2005 Silverado 3500 6.0
Seen an odd thing maf read 9.5 gps at 2500 rpm driving. Fuel trims pegged. Cleaned maf no help. What do you mean if timing is changing? My amp clamp got leant out but broke in a fan. I had 4 channels going to cyl 7 coil all looked good. Also scoped injector. What would cause misfire status to change from normal to inactive I think it said

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23 Nov 2019 19:07 #35259 by Tyler
Replied by Tyler on topic 2005 Silverado 3500 6.0

Cheryl wrote: What do you mean if timing is changing? My amp clamp got leant out but broke in a fan. I had 4 channels going to cyl 7 coil all looked good. Also scoped injector.


I was thinking if there was something wrong with the CKP that was causing the dwell time for the #2 or #7 coil to change. Seems unlikely, I know, but you've eliminated all the easy stuff. :lol:

You've probably thought of a broken valve spring? I know the vacuum gauge didn't twitch. :( It might be worth comparing running compression to another cylinder.

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23 Nov 2019 19:24 #35260 by Cheryl
Replied by Cheryl on topic 2005 Silverado 3500 6.0
I’ve never actually checked a crank sensor for a misfire on a cylinder. Do you think a misfire shows up on a crank waveform just asking. I’ll do a running compression test on the cylinders and just see. Vacuum gauge your was 20 inches solid but never hurts to try what others suggest. I got another amp clamp ordered. Going to watch fuel injectors and coils. I thought the injector and arcing plug wire would fixit. The #7 injector flowed about 5 psi less

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24 Nov 2019 15:33 #35291 by Tyler
Replied by Tyler on topic 2005 Silverado 3500 6.0
Oh really? :huh: Maybe try moving the injector? Or a secondary probe on the #7 coil wire to check for a lean miss?

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24 Nov 2019 16:59 #35292 by Cheryl
Replied by Cheryl on topic 2005 Silverado 3500 6.0
I replaced number 7 injector and scoped control on it I never lose control. Going to current ramp the coils and injectors when I get a new amp clamp. Definitely doing a volumetric efficiency test due to low maf g/s readings I was seeing plus throwing a p0101 now

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25 Nov 2019 17:13 #35314 by Cheryl
Replied by Cheryl on topic 2005 Silverado 3500 6.0
Update performed volumetric efficiency test with original maf sensor only hit 175 grams per second at 5567 rpm 67 degrees iat. New maf hit 230 grams per second at 5600 rpm same temp. Still a little low.

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25 Nov 2019 19:21 #35320 by Tyler
Replied by Tyler on topic 2005 Silverado 3500 6.0
Yeah I got 68% with your new MAF. :unsure: I know that OHV engines never make amazing VE numbers, but you'd think this one could do better.

I have a known good capture from an '06 Silverado 6.0L, and it maxed out at 263 g/s. That gets the VE to 77%, which I can live with.



Still flags a miss on #7?
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25 Nov 2019 20:05 #35322 by Cheryl
Replied by Cheryl on topic 2005 Silverado 3500 6.0
Yep intermittent missing on cyl 7

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25 Nov 2019 20:07 #35323 by Cheryl
Replied by Cheryl on topic 2005 Silverado 3500 6.0
Swapped plug coils from cylinder 2 and 7 to different cylinders on the engine. What’s weird I think is the control wire for the coils 2 and 7 are only 4 volt square waves I think there supposed to be 5 volt turn on signals. Even when not missing that’s what they show

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25 Nov 2019 20:07 #35324 by Cheryl
Replied by Cheryl on topic 2005 Silverado 3500 6.0
New injector on 7 scoped injector never dropped out.

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25 Nov 2019 20:14 #35325 by Cheryl
Replied by Cheryl on topic 2005 Silverado 3500 6.0
I’m probably going to do an exhaust back pressure test on both banks. Then check the intake system for restrictions. You know how to check the intake side besides just checking the air filter and intake boot up to the throttle body?? Do you know if these engines are known to get out of time? I’m going to scope cam crank sensors to see if timing is off. This is a roofing truck for a company this thing is beat....

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28 Nov 2019 09:03 #35399 by Tyler
Replied by Tyler on topic 2005 Silverado 3500 6.0
Easiest way I know of to check for intake restrictions is to watch the MAP at WOT. It should read barometric pressure, or maybe 1 inHg below. Much more and there may be an issue.

You can also sometimes find restricted exhaust by watching the upstream O2's during WOT. If one side truly is restricted, the OTHER side will show lean at wide open. The restricted side will show full rich.

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28 Nov 2019 09:57 #35403 by Cheryl
Replied by Cheryl on topic 2005 Silverado 3500 6.0
I knew about the rich and lean o2 tests during exhaust back pressure testing. Didn’t know about the map reading for intake restriction testing though. Think I might figured this out. Cylinder 3 ignition coil connector pin figment was intermittently making contact. Runs good now but the transmission slips
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