Hello well I’ve been having stalling problems on my 92 Mercedes Benz 400se I figured it was the throttle butterfly valve that was having a hard time opening so I used fuel treatment and i cleaned the the butterfly valve. Now after I turned it on the rpm in park and neutral is around 1800 which seems a little bit too high. However when it’s in drive its normal. Reverse is the same except for a jerking motion after i put it into reverse (the jerking happened after the cleaning) . On top of that when in drive it seems like the car accelerates on its own.

Did you get the air intake tube back on correctly after cleaning the “throttle butterfly”?

A constant high engine idle is a classic issue caused most commonly by a vacuum leak.

A frequently used method by professional mechanics is the use of starting fluid or brake wash. Simply spray around the engine with it running ( not on the exhaust ) and listen for a change in engine noise. Once You have found the area, turn the engine off and check for cracked vacuum hoses or leaky gaskets.