Faulty VANOS solenoid
Faulty Camshaft Position Sensor
Mechanical timing condition
Engine Light ON (or Service Engine Soon Warning Light)
VANOS operates on the intake camshaft in accordance with engine speed and accelerator pedal position. At the lower end of the engine-speed scale, the intake valves are opened later, which improves idling quality and smoothness. At moderate engine speeds, the intake valves open much earlier, which boosts torque and permits exhaust gas re-circulation inside the combustion chambers, reducing fuel consumption and exhaust emissions. Finally, at high engine speeds, intake valve opening is once again delayed, so that full power can be developed. VANOS significantly enhances emission management, increases output and torque, and offers better idling quality and fuel economy.
VANOS is a combined hydraulic and mechanical camshaft control device managed by the car’s DME engine management system. The VANOS system is based on a discrete adjustment mechanism that can modify the position of the intake camshaft versus the crankshaft. Double-VANOS adds continuous adjustability to the intake and exhaust camshafts.
First double VANOS system appeared on S50B32 engine in 1996. Later, BMW added double VANOS to its M52tu series of inline 6-cylinder engines, which changed the mechanism from fixed position operation to continuously variable, and added the same functionality to the exhaust camshaft, on a number of its cars. Double-VANOS (double-variable camshaft control) significantly improves torque and emissions since valve timing on both the intake and exhaust camshafts is adjusted to the power required from the engine as a function of gas pedal position and engine speed. On all BMW engines that use single VANOS, except S50B30, the timing of the intake cam is only changed at two distinct rpm points, while on the double-VANOS system, the timing of the intake and exhaust cams is continuously variable through a range of ~40 crankshaft degrees for the intake, and 25 degrees for the exhaust. The advantage of double-VANOS is that the system controls the flow of hot exhaust gases into the intake manifold individually for all operating conditions. This is referred to as internal exhaust gas re-circulation, allowing very fine dosage of the amount of exhaust gas recycled.