2015 GMC Sierra 1500 - Unknown Misfire Issue?

mamarinelli · December 19, 2023

Looking for some advise on what to try next to fix an unknown issue with my 2015 Sierra. 190k Miles L83. New transmission at 140k.

A couple months ago I had a studder while the engine was put underload at low RPM in high gears. Mostly only noticeable with highway driving. Feels like the ignition kicks out for a split second truck jerks hard then I have to let out of it and downshift to high RPM where engine is not under as much load. The issue has been slowly getting worse and happening at less and less load. I can hear an audible breakup coming from the engine bay and exhaust notes.

I started small and replaced plugs and wires, ran a can of seafoam through a 1/4 of a tank, ran seafoam in oil for 30 minutes at idle, then did an oil change with a quart of marvel and ran that for another 30 in hopes to clear a possible stuck DOD lifter. All with no changes. I reached out to a GM tech who told me its likely a stuck DOD lifter so I went ahead and replaced all the lifters and cleaned up in carbon on the injectors while I was in there. Still not changes.

I am thinking the only logical next step is to replace the coils because it sounds like a ignition issue. But before I go throwing more money at this I would like to see if anyone has any other input.

Thanks in advance!

ember1205 · December 19, 2023

Have you connected an ODB reader to check for pending / historical codes? What about watching the various sensors while driving? TrackAddict app for your phone will not only track a ton of sensors but has a recording mode so you can plug in and go then review the data logs when you get home. You can watch things like air temps, O2 sensor values, fuel trims, etc. Analyzing the data might help you track down the culprit.

mamarinelli · December 19, 2023

Just now, ember1205 said:

Have you connected an ODB reader to check for pending / historical codes? What about watching the various sensors while driving? TrackAddict app for your phone will not only track a ton of sensors but has a recording mode so you can plug in and go then review the data logs when you get home. You can watch things like air temps, O2 sensor values, fuel trims, etc. Analyzing the data might help you track down the culprit.

Thank you, I have had a misfire code come up a couple of times but nothing other than that. I do have a live scanner (Scanguage) that I can use for this information. I did not notice anything unusual other than what seemed like a pretty broad range of fuel pressure between 40-80 if I remember correctly.

Paul secatore · April 10

Hi I was just wondering if you figured your issue with your truck. I’m having same scenario with mine. Any info would be great. You can send an email if you want. [email protected]

Paul secatore · April 10

On 12/19/2023 at 9:04 AM, mamarinelli said:

Looking for some advise on what to try next to fix an unknown issue with my 2015 Sierra. 190k Miles L83. New transmission at 140k.

A couple months ago I had a studder while the engine was put underload at low RPM in high gears. Mostly only noticeable with highway driving. Feels like the ignition kicks out for a split second truck jerks hard then I have to let out of it and downshift to high RPM where engine is not under as much load. The issue has been slowly getting worse and happening at less and less load. I can hear an audible breakup coming from the engine bay and exhaust notes.

I started small and replaced plugs and wires, ran a can of seafoam through a 1/4 of a tank, ran seafoam in oil for 30 minutes at idle, then did an oil change with a quart of marvel and ran that for another 30 in hopes to clear a possible stuck DOD lifter. All with no changes. I reached out to a GM tech who told me its likely a stuck DOD lifter so I went ahead and replaced all the lifters and cleaned up in carbon on the injectors while I was in there. Still not changes.

I am thinking the only logical next step is to replace the coils because it sounds like a ignition issue. But before I go throwing more money at this I would like to see if anyone has any other input.

Thanks in advance!