Improper VANOS function will cause reduced power and poor fuel economy. The VANOS system is BMWs version of variable valve timing and can be found on the intake and or exhaust camshafts. The system uses a pair of electrically actuated solenoids that direct the flow of pressurized oil to the VANOS gears. Depending on engine requirements the VANOS system can advance or retard timing as requested by the ECU.
Proper camshaft timing control is critical to maintaining a broad powerband, crisp throttle response, and peak engine efficiency. When the factory variable valve timing solenoid begins to degrade, oil pressure delivery to the cam adjusters becomes lazy
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