My moms old 300SEL (with the M103) that was once my car is now my "work car" again as she is getting a brand new SUV very soon. I have been using the car often. Its been reliable the past 4 years we have owned it, but recently (even in this dreafully hot weather we have had) until the engine is fully warmed to operating temperature, its "cold natured" meaning that the car will misfire (a dead miss) on initial acceleration (up to about 2500 rpms) every time you pull from a stop until it warms up. If I let it warm up for 10 minutes before I leave in the mornings, its fine when I take off. Even on these hot and muggy mornings (lows in the 70s) it does this. The car had new spark plugs put in about 4 months ago, a new EHA valve, and a new fuel pump about 2 months ago. We replaced the coil about a year ago. It kinda acted like this before the coil was replaced, but it did it all of the time. Maybe that is going bad again? I used to could take off in the car at any temperature and it would run smoothly. Now something is wrong since it will "chug" and misfire on initial acceleration until fully warmed up.

What else could it be? We didnt replace the spark plug wires, could that be it?

Also, when I hit certain bumps, there is like something is causing a "thump" that can be felt through the steering wheel, but its when the REAR tires hit the bump. You cant hear it, but you can feel it. It did this before, but stopped for a while when we put on some new tires, but its seemed to have come back a little. The muffler is getting loose and had came loose from a clamp, but the muffler shop put it back on today and it still does it. Both mufflers have holes rusted and its going to cost $601. to go back with the dual pipes, or $186. if I go universal (with a single pipe), which I likely will.

Thanks in advance!