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Discussion Starter #1 (Edited)
Vehicle: 1991 Mercedes 190E 2.3 (Automatic)

I'm trying to figure out WHY my vehicle runs so rough on initial startup AND when it shifts into Drive / Reverse. I recently replaced my radiator and drained the transmission fluid / replaced tranny filter.

When performing a cold start the car starts up. The vehicle is in Park running idle. The RPM gauge reads about 1100 but then over a 5 second period falls to around 650 and it is choking, sputtering, threatening to shut off AND THEN the needle quickly shoots back up to about 1,500 stabilizing OK and then again the needle drops back down to about 650 RPMs and the car threatens to turn off; the engine (mostly the manifold side) can be seen shaking and heard squealing. Back & forth it goes for about 5 mins until finally the car stabilizes fine running at about 1,500 RPMs. Again the car is in Park running idle. I have not revved it or anything. It is currently about 1'C here in Canada.

Once the car seems stabilized at 1,500 RPMs i shift into Reverse or Drive. The RPMs promptly drop to about 700 RPMs. The car is loud and shaking but not as bad as initial start. When i shift into Neutral or Park the RPMs jump back up to about 1,500 RPMs and the car is quieter and runs more smoothly.

Can someone PLEASE help me get to the bottom of this. Why is the car so awful on cold-start AND what is the connection with Drive/Reverse?
 

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maintenance history? lasat tuneup?
 

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Discussion Starter #3 (Edited)
Thanks Jippi. I forgot to mention that...

The car has had this problem for years now. Perhaps 1.5 years ago i performed the following:

(Replaced)
oil & filter
fuel filter
spark plugs, wires & distributor cap
fuel & brake lines
air filter

I used a can of Seafoam in the crankcase and fuel tank, and recently did a transmission fluid drain, and replaced the radiator.

I have never performed a tune-up. What does that entail? Is it a DIY task or cheap at a mechanic?
 

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full tune up is basically plugs, wires, cap, rotor, oil air and fuel filter, clean the throttle, o2 sensor. i would clean and check the operation of the iacv and related hoses and take the mass air unit out and check the boot for leaks. check the duty cycle and make sure its in the middle but dont do this until you check for air leaks.
 
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