2019 GMC Yukon Denali Rough Idle

[KTBear]

I've been reading alot of the posts because I have an issue with my Yukon and a rough idle. History: In July 2025, I bought a 2019 GMC Yukon Denali 6.2L (I named the vehicle Barney - no nasty comments please) with almost 49,000 miles on. Bought it at a GMC dealership way, way across town (about 2 hours from home). Bought the extended warranty with it. (I'll also add at this time, I have not put 5,000 miles on I purchased it.) I live north of Atlanta (this really doesn't have any point to the post - just reference). I work from home so I really don't drive except around town and my occasion road trip. I have driven Barney down to Destin, FL twice and to Ocean City, MD. Prior to driving to Ocean City, I noticed it was running alittle rough. I knew we were going to be doing highway miles, I put some fuel injector cleaner in the gas tank thinking maybe because of the around town driving spark plugs were fouled. By the time we got home, still running rough. One morning as I was driving home from visiting my brother in the hospital the rough got ROUGHER! Next thing I knew the front collision alert came on the dash, then the traction control orange light came on and the engine light started flashing. I was very close to home (less than 3 miles) got it in the driveway and parked it so a rollback could pick it up. Rollback picked it up and took it to my closest Chevy dealer (the GMC dealer did tell me I could take it there). They did the diagnostics on it and said that its ignition coil #6 that was causing the problem. So they replaced it. Picked it Thursday night, drove it back to the hospital to see my brother and not even 10 miles in the drive, started running rough again! Drive it home that night and parked it. Drove it to the chevy dealer Saturday morning, they put the code reader on it and said "oh its ignition coil #2." So once again they replaced another coil. Once again I pick it up and within 25 miles it starts running rough again. Back I go with it, this time I ask for the service manager to get involved because this is the 3RD time for the same thing in less than 30 days. Coils shouldn't be going bad like this, there's something that we're missing, there's an underlaying problem we're not looking at. Is it something in the fuel system, maybe a fuel injector, (and I literally said this) could it possibly be a faulty spark plug. . . . . there's something we are missing. Can something please be the Monday morning quarterback on this and really look into it? Of course, they said yes. A few days later they call to say they can't find anything. I asked if they drove it. . . . .we drove it in the parking lot. I gave them authorization to drive it and they did drive it 30 miles. And once again they told me they couldn't replicate the problem. That it was ready and I could pick it up. In addition to the running rough, it feels like its "surging" . . . .like it wants to go faster but I'm holding it back and the dealership was aware of this issue also. So needless to say (after my long winded explanation) my "I was so excited about my new to me vehicle" is running rough and I have no clue (I feel some days that my 2003 Chevy Tahoe Z71 with 241K miles on it, runs better than the Denali). I guess I just wait for it to break down or the engine light to flash.


Vehicles I own:
2002 Chevy Silverado LT 2500HD, 4WD, 8.1L Allison Transmission - Gas (black in color)
2003 Chevy Tahoe Z71, 4WD, 5.3L - Gas (black in color)
2009 VW New Bettle Convertible - Gas (triple black in Color)
2019 GMC Yukon Denali, 4WD, 6.2L - Gas (black in color)
1964 Pontiac GTO, 389, 4-speed – Gas (saddle bronze metallic)

 

[Fless]

I'm thinking that the Direct Injection is letting the valves get dirty -- has it ever had walnut blasting done to the valves? Might be worth a look.

 

[RST Dana]

It’s not liking the fact you park it near that old GTO. Send me your address and I’ll fix that problem for you asap. Nobody should be stuck with vehicle jealousy like that!

 

[Joseph Garcia]

I've been reading alot of the posts because I have an issue with my Yukon and a rough idle. History: In July 2025, I bought a 2019 GMC Yukon Denali 6.2L (I named the vehicle Barney - no nasty comments please) with almost 49,000 miles on. Bought it at a GMC dealership way, way across town (about 2 hours from home). Bought the extended warranty with it. (I'll also add at this time, I have not put 5,000 miles on I purchased it.) I live north of Atlanta (this really doesn't have any point to the post - just reference). I work from home so I really don't drive except around town and my occasion road trip. I have driven Barney down to Destin, FL twice and to Ocean City, MD. Prior to driving to Ocean City, I noticed it was running alittle rough. I knew we were going to be doing highway miles, I put some fuel injector cleaner in the gas tank thinking maybe because of the around town driving spark plugs were fouled. By the time we got home, still running rough. One morning as I was driving home from visiting my brother in the hospital the rough got ROUGHER! Next thing I knew the front collision alert came on the dash, then the traction control orange light came on and the engine light started flashing. I was very close to home (less than 3 miles) got it in the driveway and parked it so a rollback could pick it up. Rollback picked it up and took it to my closest Chevy dealer (the GMC dealer did tell me I could take it there). They did the diagnostics on it and said that its ignition coil #6 that was causing the problem. So they replaced it. Picked it Thursday night, drove it back to the hospital to see my brother and not even 10 miles in the drive, started running rough again! Drive it home that night and parked it. Drove it to the chevy dealer Saturday morning, they put the code reader on it and said "oh its ignition coil #2." So once again they replaced another coil. Once again I pick it up and within 25 miles it starts running rough again. Back I go with it, this time I ask for the service manager to get involved because this is the 3RD time for the same thing in less than 30 days. Coils shouldn't be going bad like this, there's something that we're missing, there's an underlaying problem we're not looking at. Is it something in the fuel system, maybe a fuel injector, (and I literally said this) could it possibly be a faulty spark plug. . . . . there's something we are missing. Can something please be the Monday morning quarterback on this and really look into it? Of course, they said yes. A few days later they call to say they can't find anything. I asked if they drove it. . . . .we drove it in the parking lot. I gave them authorization to drive it and they did drive it 30 miles. And once again they told me they couldn't replicate the problem. That it was ready and I could pick it up. In addition to the running rough, it feels like its "surging" . . . .like it wants to go faster but I'm holding it back and the dealership was aware of this issue also. So needless to say (after my long winded explanation) my "I was so excited about my new to me vehicle" is running rough and I have no clue (I feel some days that my 2003 Chevy Tahoe Z71 with 241K miles on it, runs better than the Denali). I guess I just wait for it to break down or the engine light to flash.


Vehicles I own:
2002 Chevy Silverado LT 2500HD, 4WD, 8.1L Allison Transmission - Gas (black in color)
2003 Chevy Tahoe Z71, 4WD, 5.3L - Gas (black in color)
2009 VW New Bettle Convertible - Gas (triple black in Color)
2019 GMC Yukon Denali, 4WD, 6.2L - Gas (black in color)
1964 Pontian GTO, 389, 4-speed – Gas (saddle bronze metallic)

I'd love to assist you, but I honestly cannot get through a 20+ continuous line paragraph.

 

[KTBear]

It’s not liking the fact you park it near that old GTO. Send me your address and I’ll fix that problem for you asap. Nobody should be stuck with vehicle jealousy like that!

I think its because the GTO isn't black in color like the rest of my vehicles!

 

[KTBear]

I'd love to assist you, but I honestly cannot get through a 20+ continuous line paragraph.

Apologizes that you didn't want to read through. I was only trying to give the history/background. But will definitely keep this in mind for future posts. Thanks for the suggestion.

 

[LoggNM]

I have a similar symptom on a 2011 6.2L Yukon Denali that has been recently overhauled. Seems to run fine when cold, and accelerates with no discernable miss, but once it's warm an intermittent miss-like condition occurs when idling at a stoplight. The miss doesn't develop right away when at a stop - the motor idles smoothly at 600 rpm indicated for about 30-45 seconds - then develops an intermittent miss that isn't constant - seems to happen once, then twice, then often disappears for 5-10 seconds, then misses again once or twice or even three times, then settles back down, the repeats like this until I actually accelerate. The idle is rock-steady at ~600 when I first stop, then fluctuates between 500-650 when the symptom happens. Running new plugs and have checked that plug wires are seated on plugs and coils. No CEL or pending codes to track down at this point, so I'm puzzled. When the car is below operating temp, idle is elevated but steady at 650-700 rpm (no detectable misses.) I don't think this was happening when the overhaul was fresh (about 1000 miles ago), but I didn't drive the truck much after shakedown. Truck seems to have good power and runs without any indication when under load. No history from before the overhaul - bought the truck with a dropped valve seat and had it bored, heads redone, AFM deleted, etc.

Any help or suggestions would be appreciated. (and no GTO so we can rule out the jealously theory...)

 

[jfoj]

@KTBear

Saw you had posted in the 21+ section, but read what you posted.

Given the vehicle is a 2019, if the battery is original, I would replace it.

With the Collision Avoidance and Traction Control lights coming on, seems to be possible a 12 Volt power/charging stability issue. If the alternator is acting up and/or putting out AC ripple it could cause strange misfires. Additionally there may be a ground wire problem.

This is a first stab at things, but I would also get your own OBDII App and interface, for about $10 you can get the OBDFusion App for either Android or iProducts. The OBDII interface will cost you about $32, I would recommend the VeePeak BLE interface on Amazon

https://www.amazon.com/Veepeak-OBDCheck-Bluetooth-Diagnostic-Supports/dp/B073XKQQQW/ref=sr_1_3_sspa?adgrpid=187935052922&dib=eyJ2IjoiMSJ9.LNOw8b-Pi9ak6lfB6sP-_eXLy9lfstUV3rz81DfogtxDOZzn_aP5v_7eKwu06_2hNKJrJ_U2w-jdEZEMhtE1GuUgYVYHiasM2mUUBGLIJzSjt-sDA4wEP9ZlGCi7kPeWG-tdDh9y2o0gZoRiNVP5v7rXSiGIQamNeQNH06ooBQXL77v70fiaQrvEa8nrQRzBnPN-FsI49QgIKocSU1x06c85Xa1MzZL4oMPKCy-3moiasUY5mn3juXx-M-N0qG7P4t7L8MshKy9277hEjmjxfDjUwOu868YGwVHzQOvOehE.Tu7Wvx4rI4R44nBeSh4SNzJkoeh-ooDk7yjXYSYCveM&dib_tag=se&hvadid=779541627294&hvdev=c&hvexpln=0&hvlocphy=9009963&hvnetw=g&hvocijid=5698595837173252528--&hvqmt=b&hvrand=5698595837173252528&hvtargid=kwd-2074814375460&hydadcr=7513_13830543_56089&keywords=veepeak+ble+obd2+scanner&mcid=ee590f1ddb11309989bf01c6f832ea61&qid=1765907502&sr=8-3-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1

You need to learn how to use the tool and SAVE Freeze Frame data every time you have a problem. Freeze Frame data and Fuel Trim info is a gold mine when trying to sort out problems.

 

[LoggNM]

I have a similar symptom on a 2011 6.2L Yukon Denali that has been recently overhauled. Seems to run fine when cold, and accelerates with no discernable miss, but once it's warm an intermittent miss-like condition occurs when idling at a stoplight. The miss doesn't develop right away when at a stop - the motor idles smoothly at 600 rpm indicated for about 30-45 seconds - then develops an intermittent miss that isn't constant - seems to happen once, then twice, then often disappears for 5-10 seconds, then misses again once or twice or even three times, then settles back down, the repeats like this until I actually accelerate. The idle is rock-steady at ~600 when I first stop, then fluctuates between 500-650 when the symptom happens. Running new plugs and have checked that plug wires are seated on plugs and coils. No CEL or pending codes to track down at this point, so I'm puzzled. When the car is below operating temp, idle is elevated but steady at 650-700 rpm (no detectable misses.) I don't think this was happening when the overhaul was fresh (about 1000 miles ago), but I didn't drive the truck much after shakedown. Truck seems to have good power and runs without any indication when under load. No history from before the overhaul - bought the truck with a dropped valve seat and had it bored, heads redone, AFM deleted, etc.

Any help or suggestions would be appreciated. (and no GTO so we can rule out the jealously theory...)

In case this helps someone - I resolved this issue as a hairline crack in one of the (new) AC Delco sparkplugs. The plug was fresh from the motor reinstall, and appeared fine out the box, but was damaged during manufacture or got bumped/dropped somehow on its journey to me. Very subtle symptoms and no CEL - but I was able to confirm misfires on that cylinder using live data misfire counts and that lead me to inspect things more diligently. The cracks were apparent when I removed the plug because the tracking darkened the crack. Truck runs great now.