Expert: Sean Halliday - 7/1/2007

Question
runs very rough idling sounds like whistling from engine somewhere. Check engine light came on. Local Mechanic said possible plug misfire. Changed plugs OEM F7LDCR ran good for a day then Check engine light came on again and running rough again. Local Mechanic said possibly vacuum. When idling and removing oil cap vacuum intake draw through the o oil cap and dipstick . What & where could be the problem?

Answer
The whistling is a possible leak from the plug.Are the threads for the plug ok?.Can be a leak at the head gasket.All BMWS when removing the oil cap will stumble slightly as the vacuum/crank breather system is sealed.You will need to do a compression/leak down test, then a vacuum test.You havnt said what the OBD code was so its good to know what the problem is acccording to the scanner.If you find out and let me know,i can advise you further.