Low idol on my 1995 mb C220 when Im at a stop or not pressing gas. Bought from very small dealership. They changed spark plugs but its still doing it. I dont know much about these cars at all but noticed it during test drive. I told them I would buy the car if they fixed the problem because it makes the car shake and they told me to bring it back in a couple days for them to fix. Then when I left the lot and drove directly to the DMV to register it, it would not restart....as if it was not getting any gas or was out of gas, but it had a full tank! They put a new fule pump. Im very worried about getting screwed over by this dealership, any suggestions??