Z4 2.0i cold start problem
Hello, I'm Mirko from Italy. I have a BMW z4 e85 Facelift, 2.0i, N46 engine. There's a problem on cold start. The engine starts very well but then drops down to 200rpm and then resumes. The car oscillates a lot. When the engine heats up, even if I start the engine after 3 hours it starts without problems. So reading the ecu errors i see camshaft sensor A error, so i changed both sensors with oem. No more errors and the problem is still there. After checked any air leak, cleaned maf, cleaned throttle valve, changed seals. Vanos solenoids are new and valvetronic motor have been changed from BMW service last year. Spark plugs new. Some days ago i tried to disconnect a vanos solenoid connector and cold start problem disappeared. Then reconnected, cold start problem. Disconnected valvetronic sensor, problem disappeared. I used the car for some days with engine light on. No more cold start problems. In the end, i see there is an oil leak the back valve cover gasket and in a spark plug seat. Since if the valvetronic is switched off, the throttle valve starts working and the engine works well, can the gasket leak cause this problem? Sorry for my english. I hope someone can help me. Thank you very much.