BMW 840i Gran Coupe Engine is sputtering Inspection at your home or office.

Common reasons for this to happen:

• Leak in Exhaust Manifold: A leak in the exhaust manifold, which collects exhaust gases, can cause the engine to sputter or run unevenly. This condition can also cause the Check Engine light to trigger as well as present increased engine noise and poor performance from the engine. A cracked or leaking exhaust manifold can create dangerous driving condition as the escaping hot gases can melt nearby plastic components. It can also lead to exhaust fumes making their way into the car cabin.

• Worn Seals or Gaskets: There are a number of gaskets and seals in the exhaust system and if any of them are failing it can create a rough or sputtering engine. Gaskets and seals wear down over time and will eventually have to be replaced. Failing to do this in a timely manner can damage the exhaust manifold which is a much more expensive repair.

• Failing Catalytic Converter: If the engine is sputtering, running rough and has a smell of rotten eggs it is probably due to a failing catalytic converter. In most cases, the Check Engine light will trigger as well. When a converter starts to fail, it isn’t able to burn off the hydrocarbons in the exhaust, and is no longer breaking down the sulfur created by the engine. This leads to the strong rotten egg smell. Eventually the car will not start at all as the catalytic converter becomes totally blocked.

• Malfunctioning Oxygen Sensors: Oxygen sensors measure how rich or lean the exhaust gases are when they leave the vehicles combustion chamber. The vehicle computer uses this information to adjust the amount of fuel entering the engine. A dirty or failing sensor puts too much or too little fuel into the engine causing it to run rough or sputter. Oxygen sensors must be replaced on a regular basis.

• Dirty Fuel Injectors: Fuel injectors spray fuel into the cylinders. It is then mixed with air and ignited. Fuel injector nozzles can become clogged over time, which can lead to a sputtering engine, slow acceleration and the car not having enough power. Fuel injectors can be cleaned if the problem is caught early, but as the conditions worsens, the injectors may have to be replaced.

• Bad or Dirty Spark Plugs: Spark plugs are responsible for igniting the fuel in the combustion chamber. If they are not working correctly or are dirty they don’t ignite the fuel cleanly and the car can misfire or sputter. The plugs will need to be replaced or cleaned.

• Dirty Mass Airflow Sensor: The mass airflow sensor measures the amount of air that is entering the fuel injection system. It sends that information to the vehicle computer, which then delivers the proper amount of fuel to the combustion chamber. A dirty mass airflow sensor will send the wrong information the computer resulting in a rough running or sputtering engine.

• Vacuum Leak: A leak in the vacuum system can lead to a sputtering or rough running engine. As the problem progresses the vehicle can hesitate or stall when accelerating.