2021 GMC Yukon XL: misfire or rough idle

Filed Nov 4, 2026 · Engine, Fuel system · MI

INCIDENT 1: Internal Engine Failure & Excessive Oil Consumption Component / System Failed: Engine Internal Components (Piston Rings, Valve Guide Seals, Spark Plugs) Failure Description: Excessive oil consumption (1.5 to 2.0 quarts burned every 2,000 miles) leading to heavy oil-fouling on spark plugs #5 and #7. Required complete cylinder head, oil pan, and piston teardown to replace all pistons, rings, connecting rod bearings, lifters, guides, valve guide seals, and spark plugs. Safety Risk: Severe internal engine oil consumption and plug fouling create an immediate risk of engine misfires, unexpected loss of power, or catastrophic engine failure while driving at highway speeds. Dealer / Repair Shop Confirmation: Confirmed by Dealership Service Department via oil consumption tests, spark plug inspection with oil dye, compression tests, cylinder leak-down tests, and physical teardown. Warning Symptoms: Low oil warning lamp illuminated; continuous need to top off oil between routine maintenance services. Inspection Availability: Vehicle and replaced components are available for inspection upon request.

Filed Nov 4, 2026 · Engine, Fuel system · MI

INCIDENT 4: Fuel Injector Internal Short (Cylinder #6) Component / System Failed: Fuel Injection System / Cylinder #6 Fuel Injector & Wiring Harness Failure Description: Cylinder 6 fuel injector failed due to an internal electrical short circuit, causing immediate engine misfires and severe power reduction. Repair required replacing the Bank 2 fuel rail, four fuel injectors, and the injector wiring harness. Safety Risk: Immediate engine shuddering and abrupt drop in drive power while operating in active traffic creates a serious loss-of-acceleration hazard and heightened risk of a rear-end collision. Dealer / Repair Shop Confirmation: Official diagnosis confirmed by Service Center Technician via electronic diagnostics verifying the internal electrical short circuit. Warning Symptoms: Check Engine Light illuminated simultaneously with engine shaking and sudden power loss; no prior symptoms existed before the failure. Inspection Availability: Confirmed via technician diagnostics; Check Engine light illuminated along with four other warning lights- car had to be towed to dealership to be fixed

Filed Nov 2, 2026 · Engine · MD

I own a 2021 GMC Yukon XL Denali equipped with the 6.2L L87 V8 engine (VIN: [XXX]). At approximately 149,000 miles, the engine developed a significant internal mechanical failure requiring complete replacement. The vehicle was diagnosed by Lexington Park Chevrolet Buick GMC, an authorized GM dealership in [XXX]. The technician identified a misfire in cylinder #5, significant oil contamination of the combustion chamber and spark plug, and broken oil-control rings on piston #5. The technician also documented bottom-end engine noise and determined that replacement of the engine assembly was necessary. The dealership replaced the engine with a GM remanufactured 6.2L L87 engine (part number 19420611), at an estimated cost of $10,950. Although my vehicle was not included in GM Safety Recall 25V‑274 (N252494000), I am concerned that this significant internal engine failure may be relevant to the federal safety agency's ongoing investigation of L87 engine failures, particularly those occurring in vehicles outside the original recall population. I request that the federal safety agency review and document this failure as part of its ongoing evaluation of the L87 engine and the scope of the existing recall. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Sep 10, 2026 · Engine · CA

My 2021 GMC Yukon XL Denali with the 6.2L L87 V8 has experienced two significant lifter/valvetrain failures. The first occurred at approximately 6,500 miles and was repaired by a GMC dealer. That failure involved cylinder #4, including a collapsed/stuck lifter and bent pushrod. The current failure occurred at approximately 110,269 miles. The vehicle initially operated normally. While traveling about 10 mph and approaching a major thoroughfare, the engine suddenly began making a loud knocking noise and the vehicle began shaking violently. There were no warning lights or other symptoms beforehand. Three children were in the vehicle. When the driver attempted to accelerate, the vehicle failed to gain speed normally, and additional accelerator input made the knocking and shaking significantly worse. The check-engine light began flashing, and “Service ESC” and “Service Traction Control” warnings appeared, along with multiple other warning lights. The engine continued running. The driver made a U-turn before entering the major roadway and drove about 0.2 miles very slowly back home. An independent repair facility diagnosed P0305, cylinder #5 misfire. Moving the ignition coil and spark plug did not move the misfire, and the #5 spark plug was oil-soaked. A GMC dealer later confirmed a stuck lifter on cylinder #5 and advised that the failed lifter damaged the camshaft. My concern is the sudden loss of normal acceleration and severe engine malfunction without warning, especially because this same L87 engine previously suffered a major lifter failure at low mileage. I am asking the federal safety agency to determine whether repeated L87 lifter/valvetrain failures represent an additional safety-related defect or failure pattern.

Filed Aug 25, 2026 · Engine · UT

My 2021 GMC Yukon Denali features the 6.2L L87 V8 engine. This vehicle was previously serviced for the GM voluntary recall regarding engine bearing failures, and the dealership completed the remedy by inspecting the motor and changing the oil to the thicker 0W-40 specification. Since completing this recall fix, the vehicle has developed an intermittent rough idle and sputtering behavior. The dealership has been unable to duplicate the intermittent issue and claims it falls under normal behavior. I am filing this report because my vehicle is exhibiting post-recall remedy engine degradation, matching the exact failure patterns outlined in the federal safety agency Engineering Analysis EA26005 escalated on August 20, 2026. This intermittent sputter represents a severe safety hazard regarding potential sudden loss of motive power while driving.

Filed Jul 1, 2026 · Engine, Transmission · KS

Issue Description: The vehicle experienced a failure of the Dynamic Fuel Management (DFM) system, resulting in a collapsed lifter. This caused a cylinder misfire and a sudden loss of engine power while driving at highway speeds. Safety Concern: While traveling at highway speeds, the sudden misfire and loss of power created a dangerous condition. The vehicle could not maintain speed or accelerate properly with surrounding traffic, significantly increasing the risk of a collision. Failure Details: The issue was diagnosed as a collapsed lifter related to the DFM system. This caused persistent misfiring, rough engine operation, and severe drivability issues. Repair Outcome: Due to the extent of internal engine damage caused by the lifter failure, the vehicle required complete engine replacement.

Filed Jun 6, 2026 · Engine, Seat belts · OR

While I was driving home from the grocery store with my 4 kids our 2021 GMC Yukon XL (5.3L V8 engine), the vehicle suffered a sudden, catastrophic mechanical engine failure without warning. The engine began violently shaking, lost major propulsion, and dropped into a severe misfire state when we were coming down the highway. This created an immediate safety hazard on the road, as I suddenly lost the ability to safely accelerate or maintain highway speeds while hauling my children.A certified technician diagnosed the issue as a complete failure of the active fuel management hydraulic valve lifters and bent pushrods, a known manufacturing defect explicitly documented in GM Technical Service Bulletin PIP5776F. The internal failure required a total engine teardown and valvetrain replacement, costing over $10,000 out of pocket.General Motors has failed to issue a safety recall for this specific 5.3L valvetrain defect, despite it causing unexpected engine stalls, severe power loss, and immediate traffic hazards for drivers. This defective component poses an ongoing safety risk to families and should be upgraded to a mandatory safety recall. I am afraid to drive it every time I get on the highway in fear it could shut down again.

Filed May 24, 2026 · Engine, Fuel system · LA

The vehicle suddenly began vibrating noticeably when idling and at low speeds. About 30 minutes after this started happening a warning lamp lit up. We drove the vehicle about 2 miles to a local auto parts store to get an initial computer diagnosis of the issue. The test resulted in a code of "P0304" which detected a cylinder #4 misfire and recommended a fuel injector replacement. We brought the vehicle to a local mechanic to get the issue further evaluated. After this evaluation, it was determined that the cylinder #4 misfire was related to a lifter failure. The mechanic explained that this situation could possibly have caused more damage, specifically to the camshaft, but that job was bigger than he was willing to take on. He recommended we get the vehicle towed to the dealership for further evaluation. He also informed us that this situation was common with the engine in this vehicle and GMC is aware of it. He directed us to some articles online that elaborated on the potential known issues related to the automatic fuel management (AFM) system and the related engine damage. The vehicle was towed to a local GMC dealership for evaluation. They found the failed cylinder #4 with associated lifter failure and damaged camshaft. We went forward with the repair at the dealership. We asked the dealership about the known engine issues with this vehicle. They acknowledged the widespread issues but informed us that our particular VIN has not been included in any recalls or safety notifications, so we were responsible for the repairs. The vehicle spent nearly 3 weeks at the dealership. One of the parts was on backorder due to a national shortage, which delayed the repair by about one week. That seems to imply that the parts involved in this repair are in high demand, which raises the question of this being a manufacturing/parts issue that may need to be investigated further.

Filed Mar 25, 2026 · Engine · NC

2021 Yukon Denali 6.2L V8, 137k miles- engine failure—driving down road 55mph and engine light came on, along with check esc and check traction warnings, vehicle began to rough idle and shake, motor knocking. Personally feel this is related to recall but my vin not included says dealership- I feel this recall is affecting way more vehicles than vin’s included. Dealership charged 220$ to plug it in, codes weren’t specific for problem. They are stating “lifter is bad and possibly cam, won’t know if the lifters scarred the cam until they take it apart” and charge me at least 6k is price quoted. No warnings at all before this happened. 137k miles so out of warranty. This put myself and kids in dangerous riding condition as I had to stop and have vehicle towed to dealership.

Filed Dec 31, 2025 · Engine, Suspension · KY

12/16/25 (evening): Warnings began cycling across the screen: 1) Service ESC, 2) Vehicle Leveling for Stability, 3) Rear Axel System Off, 4) Engine symbol began flashing, and 5) Service Traction Control. I felt vibration/bouncing while driving as well. 12/17/25 9 AM: Took 2021 GMC Yukon Denali to GMC dealership. They ran a computer scan and reported a misfire, but nothing else appeared to be wrong. They told me that sometimes a low battery can cause the warning lights and messages to cycle. They recommended that I keep driving it and return if the warnings appeared again. 12/17/25 9:18 AM: I left the dealership. I drove 4.5 miles, and all the same warning lights came back on. When I pulled into a parking lot, it smelled like my engine was on fire, and dark smoke was coming from my rear exhaust pipe. I called a flatbed tow truck and had the car returned to the dealership. Mileage: 52,285 GMC 2021Yukon Denali XL 6.2L V8 engine Well-maintained with regular oil changes. The dealership told me there was a lifter failure and that the engine could be damaged and would need to be replaced if the cam, pushrods, etc., were damaged. They also told me I was out of warranty by less than 60 days. The dealership said my warranty expired in October 2025, even though my vehicle is a 2021 with only 52,285 miles. They just informed me that the left lifter was replaced at 6,000 miles and that they will replace the right lifter. I am concerned about further damage down the road, given the recalls on the GMC 6.2L engines.

Filed Aug 25, 2025 · Engine · OK

On Thursday August 14 while driving our traction control light and engine light came on along with the ESC light while traveling out of state. The car felt like we were driving on a rumble strip. We immediately took it to the nearest auto repair shop, only a few minutes away. They reset the battery and dash lights and we took it for a test drive. All the lights came back on after a couple of feet and loud knocking sounds started. Our emissions light then also came on and a strong exhaust smell was emitted. Each time the engine was started the knocking grew louder and the engine was severely struggling and sounded very wrong . The shop put their diagnostic tool to use and identified misfiring on cylinder 5. Upon further inspection they identified camshaft irreparable failure. We had it towed to the Platteville WI GMC Dealership Friday Aug 15. Where they confirmed camshaft failure and informed us our engine needed total replacement. Our safety was at risk since our engine failed while exiting the highway.