I'm having an issue with my 97 E320. Occasionally, more often than I care to tolerate, the car seems like it can't find idle when I decelerate to a stop from normal in-town driving speeds.

When I pull up to a stop, the cars RPMs will vary from 500 to 1000 (or a little more either way), like it's searching for the correct idle. If I hold my foot firmly on the brake, it will eventually stop, or if I put the car in neutral and rev the engine slightly, it will go to a normal idle.

I have no error codes, and the dash doesn't indicate any problems. Has anyone heard of this kind of issue before?

 

could be a vacuum leak with one of the vacuum hoses or EGR problem or spark issue

 

Wouldn't the EGR or spark problems show up as a system fault?


Update: I just ran across town and received an electronics fault / check engine message.
I plugged in my code reader and it says it's a G3 G4 Ow Cat - Front Right.

Anyone know if the symptom of this failure would be the surging that I see in the OP?

 

I noticed something similar in my car, when at a stop it does this? no codes at all. Did the changing the cat rectify the problem?