got a chk eng light 2days ago. ofcourse a tune up was suggested and completed. new ign coil and plugs and gas filter. filter and oil change also done. it is now 2 days later and the chk eng light is back and the car won't stay started. it bucks like a old truck and sounds scary. I won't even drive it to the shop. what gives here? any help will be greatly appreciated.-mybanginbmw.com