Bad Idle, Think it's the EGR ? Check this first

[Cone Killer]

My 240 was idling rough, and the CEL was on, pulled the code and it was the EGR valve. I found a small vacuum elbow line that connects the EGRC-BPT valve to a main vacuum source had a hole in it. Replaced the line, cleared the codes, and it idles smoothly again. Just a heads up for anyone dealing with a EGR problem. Also, I had to loop a longer piece of vacuum line to make it work since I couldn't find any parts store that had a pre bent rubber line.

[Novalou]

Thanks for the info, but how do you clear the codes? unplug the battery?

[Cone Killer]

Well, yes and no.

After the "repair" I cleared the the codes on the ECU by turning the screw back and forth per the manual which cleared the code. Then for good measure I disconnected the battery for 10 minutes. I just took the car out for a long 15 plus mile test drive via interstate and local surface streets. She idles perfectly now, and I'm not sure if this is just in my head, but seems to accelerate much more strongly between 70 and 80 mph in 5th gear.