My 2007 mini cooper with low milage (40,000) began making clacking noizes, then backfiring, then loosing power. Had intake valves cleaned with walnut shells a few months ago at graet expense and just started to click and clack again. Suggestions? Has anyone else had this problem. Put in feul injection cleaner and has stopped for now.
Are you using premium fuel?
AFAIK, most european cars require it.
Are you using cheap fuel?
Have you checked the oil level recently?
Using less than the minimum grade fuel will contribute to carbon build-up that causes pre-ignition and knocking. IIRC, the Mini Cooper requires premium fuel. Using regular or mid-grade is probably the cause.