I went ahead and allowed a local mechanic to look at the car. Since we are new to the area (Cleveland, OH), I asked around and found that this shop services most of the older mercedes in the area. I described the problem and asked if they could run a fuel check or related test to attempt to determine the problem. The owner told me they would take care of it.

The first time it was in they changed the spark plugs with Bosch copper plugs (I had the Bosch platinum plugs in when I dropped it off) and placed a 'miracle' bottle of injector cleaner in the gas tank. The mechanic told me to drive it for a little while and see if I noticed any improvement - there was no improvement. They did not do anything else.

The second time I took it in, they replaced the distributor cap, rotor, put another 'miracle' bottle of injector cleaner in the gas tank and adjusted the CO mixture. They had the car for a week before I got it back. There was no improvement...

Am I wasting my time with these guys? I stopped by and told the mechanic that the problem still exists and after two visits, the car has shown no improvement. He told me that cars this old have fuel problems like this and that they were attempting to fix itimprove it without having to replace some expensive items like the fuel distributor or a full set of injectors - if they ended up being the culprit. I asked what they would do if I brought it in a third time and he said they would attempt to adjust the mixture again and run a compression test to help determine the problem. Should I be looking somewhere else for a diagnosis?

Thanks in advance for your replies.