1st Generation Mercedes-Benz M Class Rough Engine Idle

Mercedes released the first generation—the W163—of their wildly popular M Class in 1997 as a replacement for their 11-year-old G Class, and the hope was that the M Class could fill the luxury midsize SUV slot between their GLK Class and the GL Class. Some owners experience a rough engine idle with their W163.

Cars that run smoothly do so because they are getting the perfect mixture of fuel and air passing in to the cylinders. If there is too much air, the car will not have enough power. Too much fuel, and the rich mixture will cause the MPG rating to drop and the engine to flood. The smoothness of the car is also due to all the cars cylinders firing properly. If either one of these operations is interrupted, the W163 may experience the uneven idling and shaking mentioned above.

Common culprits for such problems are the spark plugs. These little guys make sure that all the cylinders are firing properly and on time. When the plugs start to go, so does the smooth firing of the cylinder, indicating that the plugs might need to be replaced. The engine coil could also be where the problem lies. The coil slings the low-voltage electricity from the battery around until it becomes the tremendously high-powered force needed to run the car. If the coil is damaged or corroded in any way, it could drop sparks, resulting in the misfire of certain cylinders. Finally, the MAF (Mass Air Flow) sensor might not operate properly. The MAF ensures that the proper mixture of fuel and air mix before entering they cylinders, and an improper mixture often results in just such erratic idling problems.

Clearly this issue does not have one simple fix. Poking around on your own may lead to some interesting discoveries, but it could also result in further damage to your car’s somewhat delicate systems. The best course of action is to schedule an appointment with a nearby Mercedes-Benz maintenance garage for a complete diagnostic of your car.

Search for a local, independent Mercedes-Benz repair shop with Mercedes-Benz mechanics that have dealer-level expertise at a fraction of the expense.