I have an E60 2006 530d M sport. 3 of my glow plugs were dead for several years. One winter the car would not start first time so I ran a diagnostic that showed all 6 dead. I replaced all 6 and the controller. The error went away. The car still struggles to start in the cold conditions now. The first time I put in the key and press start the engine turns but does not fire up. So I stop and try again. The second time the glow plug indicator flashes for about 1 second before the engine starts to turn. It usually fires up at the 3rd or 4th attempt. Any ideas? Thanks.