2021 Mercedes-Benz GLC 300: misfire or rough idle

Filed Jan 8, 2026 · Engine, Transmission · CA

Vehicle Information: Year: 2021 Make: Mercedes-Benz Model: GLC 300 Engine: M264 Mileage at time of failure: Approximately 65,000 miles Complaint Description: While driving, my 2021 Mercedes-Benz GLC 300 began experiencing repeated engine misfires and rough running, accompanied by a persistent check engine light. These symptoms began shortly after I purchased the vehicle and progressively worsened over time. The vehicle exhibited reduced engine performance and hesitation while driving. The condition was intermittent at first but became more frequent, indicating a progressive mechanical issue rather than a sudden failure. At approximately 65,000 miles, the vehicle was evaluated by an authorized Mercedes-Benz dealership and diagnosed with a catastrophic cylinder head failure, requiring full cylinder head replacement. The estimated repair cost is approximately $8,000. The vehicle has never been modified and has not undergone prior engine repairs. The failure occurred well before what would be considered normal wear for an engine component of this type. Based on the progression of symptoms, the dealer diagnosis, and similar reports from other owners of the same model and engine, this appears to be a systemic defect involving the cylinder head and valve train, rather than an isolated incident or maintenance-related issue. This condition presents a potential safety concern due to loss of engine performance, drivability issues, and the risk of reduced power while operating the vehicle.

Filed Dec 30, 2025 · Engine · NJ

While I was driving on the Garden State Parkway, my vehicle experienced a sudden loss of power and persistent misfires and my check engine light came on. I was put in a position of a significant crash risk due to the fact that the vehicle loss sudden acceleration power while entering the parkway. I was almost rear ended by another vehicle. I drove immediately to a Mercedes-Benz dealer. The dealer confirmed a catastrophic cylinder head engine failure. The vehicle had only 39,000 miles. After some investigating, there have been numerous complaints from vehicle owners with the same issue on the M264 engine (which is what my vehicle has). I request that the federal safety agency investigate the premature cylinder head engine failure. Not only was I put at risk for a possible significant accident, the manufacturer has refused to consider some reimbursement for my $10,000 repair. The vehicle was only 3,000 miles out of warranty at the time of the engine failure. A safety issue seems to be warranted and possibly a recall because of the many complaints on the GLC website. Please investigate.

Filed Oct 24, 2025 · Engine · AZ

Car has experienced rough idling, sluggish to no acceleration, check engine light illuminates and no shifting of gears regardless of speed. It appears to be going into limp mode. This has occurred monthly for the last four months. After pulling over, the car is turned off, wait five seconds and then turn it back on the car operates like nothing has happened. Here is when it has happened: 1.In a drive-thru lane to get some food 2.Waiting in a left-hand turn land 3.Driving through a parking lot at 10 mph 4.Driving on a road at 45 mph The date below is the last occurrence.

Filed Mar 22, 2025 · Engine · OK

On [XXX] my GLC 300 AWD while driving back from work started shaking, went into limp mode, engine started misfiring and check engine light came on. Pulled over into a parking and called Mercedes-Benz road side assistance, they sent a tow truck and the car was towed to the Mercedes-Benz of Oklahoma City. The service department informed us of cylinder head failure and told SUV needs cylinder head replacement that would be covered under the extended Mercedes warranty. As of March 22, 2025 SUV is still at the Mercedes dealer and not fixed. This is the second time in past few months GLC went into limp mode and lost power and acceleration while on road, it was towed to the Mercedes dealer. They initially said they couldn't find anything wrong but later performed an update of engine management software on the recommendation of Mercedes-Benz USA. Car was fixed at that time. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Mar 3, 2025 · Engine, Fuel system · NC

High beam can't auto dim Fuel pump fail to operate, misfires, and shut down while driving

Filed Apr 26, 2021 · Engine, Fuel system · 90 miles · CA

On april 21, 2021 at about 1800 (time), less than 45-hours after purchase of the new 2021 glc 300 vehicle, the internal combustion (engine) misfired and abruptly malfunctioned while in steady acceleration at 65-MPH. My family and I were headed eastbound on the ca-60 freeway in lane three (leftmost, fastest lane). As soon as the engine spontaneously sputtered, it abruptly stopped and intensely shook the entire car vigorously, aggressively, and continuously with no ability for control nor for the option to continue to accelerate. There were three cars behind my vehicle also accelerating at the speed of traffic (65-MPH) that also abruptly screeched to a halt to steer clear of my unusually malfunctioning vehicle. This was the most traumatic event that has ever happened to myself and my family in our lifetime. As you can imagine, we feel extremely fortunate in having survived this horrendous, unexpected, and cruel safety risk as no collision was fortunately reportable. The vehicle's malfunctioning and performance issue had placed us in an extremely high-risk of safety concerns and near moments from my or my family's health-related tragedy as the halt of numerous cars within the freeway closely swerved-away from our direction. As you can imagine, we are severely, physically, emotionally, and mentally distraught due to the manufacturing defect to the 2021 glc 300 engine. After 30-hours of continued questioning, analysis and discovery, it was confirmed of valve train component defect causing major downstream effects to the engine and immediate inability to accelerate on the highway with direct serious life threatening risk to a new vehicle and my family within it. Please consider this detrimental incident for other's global safety through my tragic experience.