My c180 (97) MISFIRES BADLY, IDLES VERY LUMPY AND HAS NO POWER.WHATS WRONG WITH IT, IS IT THE COIL PACK?

MERC C180 1997. INTIALLY STARTED TO IDLE POORLY, THEN MISFIRE, NOW VERY HESITANT WHEN DRIVING, JERKY AND WITH NO POWER.....TRIED THE AIR FLOW SENSOR..GARAGE CANNOT DIAGNOSE FAULT.IS IT THE COIL PACKS.........ANY HELP WOULD BE APPRECIATED