I am a fairly new MB owner: 1988 300 SEL. My CEL came on recently, and the car has had a rough idle at start and stops. I took it in to the shop and they told me that I needed a new air mass meter. It seemed like a simple enough job so I ordered the part. Then my cruise control began to fail. It doesn't turn on at all now. After some research it looks as if my problem might be one of three things:
1. throttle actuator
2. air mass meter and separate cruise control issue or
3. some sort of vaccum leak.

It seems that the only way to figure out whether one of the first two is bad is to change it out. But the vacuum lines I can check first, I just don't know how. I have some experience with cars ie: change out the occasional carb, or water pump, but nothing too dramatic.
My question is: how do I check vaccum lines? Which ones would be important to check in this instance?

And do I need to see if I can cancel that air mass meter order and start with the actuator? Thanks for your help.
eric zacharias

1988 300 SEL
1964 Ford Falcon
1994 Isuzu Rodeo