🟢 BMW 3 Series E90 320i N46 VANOS fault rough idle

Rough idle, hunting at idle, and reduced power. Engine management light with codes relating to VANOS timing. The N46 engine in the E90 320i has a known VANOS solenoid seal wear issue. The seals harden with age, reducing oil flow to the VANOS mechanism and causing rough idle and timing errors. Replacing the VANOS solenoid o-rings and cleaning the oil strainer screens resolves the fault. This is a DIY-accessible repair costing a fraction of a full VANOS replacement.