There is a fairly common problem with the check engine light on many BMW models. Sometimes it comes on for a good reason but other times there seems to be nothing wrong. Here is some quick information to help you determine whether you need to bring it in for maintenance.
The check engine light comes on and the car is riding rough:
There are many reasons why a check engine light and rough running could occur. Different models have different common issues. Usually the rough running is a sign of misfires – this is often caused for example, on the V8 engines by a failure of the ignition coils or a collapsing vacuum hose.
On the 6 cylinder engines, rough running when the engine is cold can often be caused by a failure in the PCV valve system. This is extremely common in cold weather states and was originally subject to a recall. If left unchecked, the valve can actually pull oil from the sump into the combustion chambers and as in one case we saw, actually oil lock the engine.
The check engine light comes on and the car is riding fine:
Very often, a check engine light and a well running engine are a sign of an emissions leak. However, the BMW 6 cylinder engines often suffer from a failure in the intake air boot located between the mass airflow sensor and the throttle body or a failure in the intake flapper valve seal. This allows un-metered air to be drawn into the engine and causes a lean running condition – great for gas mileage, bad for the engine. This may cause extended cranking during engine start up or a no start condition. Idle speed fluctuations may also be noticed with the engine running.
Bimmex has the latest diagnostic tools to scan, re-program and reset most issues pertaining to the service engine soon light. While the most common sources of these notifications are air leaks, other common ones are stuck thermostats, clogged air filters, bad oxygen sensors, dirty mass air flow meters and fowled spark plugs. Whatever the case may be, Bimmex can fix it properly and get you back behind the wheel.