Mercedes: mercedes, distributer cap, engine temp

Question
QUESTION: i have a mercedes cosworth 2.5 16v    when i start the car from cold the idle goes up and down between approx 500-900rpm and then stalls so to compensate for this i get the revs to say 1300 where it still fluctuates until its 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 1100 the 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 1800 - 3000rpm the car hesistates/misses and sometimes backfires however at 3000rpm + there is no problem at all neither is there any hesistation when accelerating in first gear  for

ANSWER: Jon,
Aside from keeping rpm at above 3000 in all gear changes not much to do....May cause a few tire squeals though.:-))
Seriously....
Questions:
How many miles since the plugs were changed. Have the plug wires ever been changed?
What grade of fuel are you burning.
How many miles since you added injector cleaner to the system.
Is this rpm fluctuation apparent at all temperature ranges. 40F above or below.
Only in cold weather? or in high temperatures as well?

Let me know OK?

Rob


---------- FOLLOW-UP ----------

QUESTION: rob i havent had the car long so i dont know when things were changed the plug wires look original ive changed the distributer cap and rotor and have new spark plugs to go in new plug leads and a spark plug spanner are coming in wednesday from mercedes the car runs on premium unleaded  the rpm fluctuation happens i think when the engine temp below 40f the outside temperature makes no difference would changing the leads get rid of the missing problem

ANSWER: jon,
Sorry it took time to respond. If you have installed new wires and still have the cold start problem, I would add techtron fuel injector additive or Seafoam.
Your injectors may be dirty. Run the vehicle near empty, add the fuel additive and fill the vehicle with a NON ethanol highest octane fuel.
operate the vehicle until until you are sure that the system has been purged and your are sucking the doctored fuel.
Take the vehicle out and run it like a scalded dawg.
In an area where there are no other vehicle and keep it under the speed limit. Keep it between the lines.
If after some time you are still having cold start problems, you should take it to an  independent Mercedes mechanic for testing.
Good Luck
Rob



---------- FOLLOW-UP ----------

QUESTION: rob thanks for advice i changed the spark plugs which got rid of the hesistation/missing problem changed the plug leads didnt make any difference added injector cleaner didnt make any difference so then i changed the over voltage relay and bingo no stalling cutting out etc runs great now only slight problem is when i start it up from cold i have to warm the engine up for a couple of minutes because it wont idle til it gets to about 45degrees i think this is the cold start injector ? anyway thanks for your suggestions

Answer
Jon,
Great that you solved many of your issues. Yes it could certainly be the cold start injector. Because the injector is used during cold start only, it takes some time to clean it through the fuel additive. You may be able to remove it and have it cleaned or replace it, but I am not sure about that.
Rob