Hello, new to the forums here. I did a search before posting, but couldn't find any hits.

The vehicle in questions is a 1999 E300D.

I am having this issue where when I'm coming to a stop or slowing down, the engine's RPMs are not smoothly coming down to idle.

The car starts, idles and drives fine.

As I'm slowing down to a stop, the engine's RPMs/"deceleration" is not smooth. The best way I can describe it, is it "bounces" down. Similar to when you let a basketball fall on the ground and its bouncing motion becomes smaller and smaller over time. The time it takes the engine to come back down to idle is normal, just doesn't come down smoothly.

What could be causing this? Hope that makes sense and thanks for the help!

I have not seen this particular issue but my first thought is the drive by wire system. Look at the under hood end of the throttle cable and see if the electromechanical device moves smoothly.

__________________
Jim

Thanks for the reply, will check it out.

I checked it out today and it is smooth. Will have to do some more research. I will post a video so people will hear how it sounds. Thanks!

Could be air in fuel lines, try to rig a torch up under hood and a camera phone recording video and go for a drive keeping revs up using the lower gears.
The idea being the higher revs will highlight the lack of fuel if any and you will capture it , normal driving may not show it up it and it could need a few minutes of high rev driving for air to occur.

Point the camera on the plastic fuel lines?

Link to video.
https://youtu.be/8i6YfazttzE

Yes camera on the plastic lines.
I have watched the video and it drops back to around 1100 rpm ish and then slows and chugs down to tick over , it should just drop to tick over and idle.
I suggested air in fuel lines as I have years of running veg oil /biodiesel and am
familiar with most odd symptoms but I think air can be ruled out here.

Its been suggested to check throttle pot unit at base of windscreen and cable and throttle pedal to ensure all ok and going back to physical stops etc and I think this is a good idea to rule any moving parts out before actually checking values from the throttle pot itself.
Egr valve could be a culprit but I do not know when it comes into play at or before idle.

I think air is causing all or at least some of the issue. I looked at the lines before starting the engine and there was air in one of them. I had the it started and saw some air bubbling moving...I did buy all those plastic white lines, which I was planning on changing any way, so I'll start there and see what happens. Thanks for now!