'15 GMC 6.0L 3500 Random Misfire 8700 Miles - Help

[BearOleMiss]

Re-posted from wrong sub forum, hope this is the right one.

 

Hello everyone. I operate a business and have several work trucks, most being 1-ton's with flat beds, with welding machines on the back. The last work truck I purchased was a brand new 2015 GMC 3500 with no bed. I installed the flat bed and put all my welding equipment on it here at my shop. The truck worked flawlessly for the first year or so.

 

I run a welding fabrication company and my rig trucks are pulled into shop and locked up each and everyday. Some days the trucks will be cranked up for 1-2 minutes and pulled out into the front of shop. In the afternoons they will be pulled back in and locked up. This could happen for several days in a row or maybe a week. Sometimes they will be run everyday on local jobs and run 20 miles or less. I take care of all of my equipment and do regular oil changes when necessary.

 

The particular vehicle in topic is a 2015 GMC 3500 HD with 6.0L gas burner (8'700 miles). It has passed 3 year warranty. It has had selected "bad" spark plugs replaced maybe 12 spark plugs in total. The truck would start running bad while driving and start to have a hiccup and bad idle/misfire. I would take it to the dealership and they would diagnose it with a random misfire in cylinder "x" and they changed the plug in question. The cylinder(s) were mostly different each trip in. I would receive the truck back, codes cleared, and the truck would continue to run like a top for several months before issues arose again. I would take it back and they would change the spark plug(s) and problems gone. I don't have the code on hand at the moment but I remember hooking it up to a snap on diagnostic tool and the code was random misfire. I vaguely remember the code being p0300. I have since bought OEM spark plugs myself once. I hooked up diagnostic tool and it showed cylinder #7 had a misfire. I replaced #7, cleared code and issues went away for months. The problem just came back again this week and I am near sick of changing spark plugs on a vehicle with 8700 miles on it. What should I do, what could be causing this issue?

 

 

Let me know if any more details would help.

 

 

Thanks, Bear.

[MNorby]

Maybe swap coil/wire with the one next to it and see if things change or follow. 

[BearOleMiss]

1 hour ago, MNorby said:

Maybe swap coil/wire with the one next to it and see if things change or follow. 

I can figure out which spark plug fouls out. I want to figure out why this is happening on an engine with 8700 miles on it.

[jhplak325]

2015’s have a 5 year/100,000 mile Powertrain Warranty, so it should still be under warranty. 

[MNorby]

my thought was if you have a bad spark from the coil see if moving the coil over moves the problem as well

[rocnrol]

How noticeable is the misfire? Does it throw a check engine light?

I have noticed on my '15 2500 that when the truck is idling it'll have a little misfire to it.... But it's almost imperceptible

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