i have a mercedes cosworth 2.5 16v when i start the car from cold the idle goes up and down between 500-900rpm and then stalls so to compensate for this i get the revs to say 1300 where it still fluctuates until it warmed up to 80(normal temp)then the car idles at 1100 which i think is right for this car . when im coming to a halt the car often stalls even when warmed up. sometimes when idling at 1100the idle will rise say 100rpm and then the engine will cut out. after any of the above i can start the car again no problem. also between say 1800-3000rpm the car hesistates / misses a bit and sometimes backfires. however at 3000rpm + there is no problem at all neither is there any hesistation /missing when accelerating in first gear.