Hello there, I recently took my 1989 300E W124 to the mechanic. I got it back and everything seemed great it drove great it was silent and it all was well. What I've noticed and I told my mechanic was that my cars rpm will vary depending if the car is cool or hot. Meaning when I turn on the car it is all good rpm are great and the car is driveable. After like 15 minutes of driving the cars rpm start to drop. They are supposed to be around 9k rpm while in Parking or Neutral and around 7k to 6k when in Drive or Reverse. Like I mentioned after about 15 minutes of driving my car starts to drop the rpm to the point where it just cant stand being on and it shuts off.

The rpm while in Parking and Neutral drop to 5k rpm and while in Drive or Reverse they are super low, the car cant stay on and it just shuts off. Is there anything the mechanic could have missed? Is it a quick fix? Ive been without my car for a long time now and I just want it up and running.

I can have the car on if I press on the gas pedal and stand on the break at the same time. That way I can get the rpm up to 9k rpm. Another thing I noticed was that my car takes a while to turn on! If I barely tap the gas pedal it turns on right away.

Any quick solutions for these problems?