Over the past few months we’ve seen a fluctuation of clients experiencing problems with their Mini Coopers due to carbon build-up in the intake valves. The cars that have this problem exhibit a range of symptoms from a rough idle or misfire condition to a check engine light. Though this problem can happen on some other BMW products, we’ve noticed it most recently on Minis with the 1.6 liter (4 cylinder) direct injection motor.
Some people may describe the symptom they experience as a surging, jerking, hiccup, or misfire. Sometimes it happens when the car is started cold in the morning, sometimes it happens while driving the car.
To remedy these symptoms, a carbon cleaning procedure must be performed where the intake valves are de-carboned with walnut blast media and in some cases would include replacement of the spark plugs and ignition coils, if necessary.
A preventative measure we like to recommend is to replace the engine oil more frequently than what the manufacturer recommends. Doing an oil change every 7,500 miles is acceptable, but every 5,000 miles is ideal.