Bzak1pgh, Too many possible problems/solutions to just guess and throw parts at it. You can go to most any auto parts store and get the car scanned for free. With a diagnostic trouble code DTC you will have someplace to start making repairs. Try scanning the car as a Mercedes 2004 SLK 320. When you get the code be sure to write it down and get the exact code, not just some explanation, get the code.