Apologies for the length of this mail! My SLK 230 1999, 46k, intermittent use but regularly serviced and always reliable UNTIL after 5 weeks non-use and flat battery, restarted by mechanics jump leads and driven back to their (non Merc) garage for a service. My opinion after 2 secs of 'tappet rattle' was that it ran as smoothly as ever. Collected car after oil/filter, coolant, brake fluid change service, their report 'slight mis-fire, suggest plug change'. Slight misfire??! .. I could hardly get it to move back up the ramp to their work-shop. It continued to run lumpily throughout the warming up. They examined plugs whilst I watched, all were clean, and other than slight mis-colouring on the ceramic appeared OK. No surprise to me to be told later that plug change had not improved the running. Now, after 'analysis' they propose renewing both ignition coil packs. Their analysis report sounded vague. Are both ignition packs likely to fail without any prior warning or performance degradation? Their opinion, when pressed, was that after driving it less than 1 mile from collection it started mis-firing. (I cannot believe that with the degree of mis-firing I found on collection, that they even offered the car back to me). I fear they are incompetent. Should I cut my losses and move the car to a Merc expert before I find that changing the packs has not solved the problem. All comments appreciated!