I just bought this car, and was told it was previously owned by a mercedes mechanic. The kid I bought if from, obviously had it warmed up before I got there, as it ran fine, but idled a little rough. He said probably a plug problem. So, I take it home and the next morning I had to turn the key for a minute or two and hold it for it to start. It starts unbelievably hard when the car has been sitting for long lengths of times. It also backfires until it has been driven for a few blocks. Once warmed up, it's fine, but still idles a little rough.