I have 88 w124 coupe with 103 engine. I experienced a similar problem. No acceleration when initially stepping on the accelerator. Motor would sputter and spit the eventually accelerate normally. Sometimes it would sputtrer and spit and I would have to pull over. I read a thread about adjusting the air/fuel mixture on another forum. On my car there is a small cylinder on top of the fuel distributor which on most cars is covered by a small ball. Mine had been removed. You need to remove it. You take a 3mm allen wrench and insert it into the cylinder while the engine is running. If you push the wrench in too far the engine will stall. You need to feel the wrench engage and turn it left to lean right to rich. Probably left to lean to correct your symptoms. The correct method on my car is to use a multimeter an plug the positive into #3 port (positive) and ground the other wire on the meter. You should try to set it at 51%. However you can put the coon tune on it by just experimenting with small turns in either direction. ie= turn to left a little- drive it. etc. etc. My car has Ktronic fuel injection system. I don't know if this applies to your car but I did this prior to buying and replacing parts and it fixed the problem.

Side note
 

I saw that you are from Dowingtown, PA. My father is from Dowingtown. We used to go there every summer to visit his mother and his sisters family. My dad was captain of the Dowingtown High School Football team in 1935 or 36. Good luck with your car. I did change spark plugs on my car before adjusting the air/fuel ratio but there was no change in performance.

Wiring harness is the most likely culprit if it hasn't been changed....change it !!

I just wanted to let everyone know that a “complete tune-up” seems to have completely resolved my issues. My Indy provided new plugs, wires, air filter, fuel filter, and cleaned the injectors. My car runs great!!!

They were so busy that I wasn't able to discuss things with them to determine if they checked other things, but my car seems totally fixed for now.

I graduated from Dowingtown High School in 1974, so your dad was before my time. My son goes now. This is a nice place to live. It is a beautiful green rural setting, with great access to big east cities and to the coast. We don't have too much severe weather, like tornadoes or hurricanes. We also don't have huge fires or earthquakes. All in all, I think this is a pretty great place to live and work and raise a family.

I like mine, too. After my new O2 sensor and plugs, I started getting the Check engine light. Arthur helped me troubleshoot, and ended up that reseating a few vacuum lines cleared that up. Now the car runs really well. As I now have a) new wiring harness, b) new head gasket and c) new AC evaporator car I hope to drive it another 100,000 miles.

Wow, you really are committed to your car, or maybe you should be committed to an insane asylum. Actually, it probably will go at least another 100K. I go back and forth almost constantly about spending more to fix things on my car. For now, I am still just fixing something if I absolutley have to do it to drive the car.

Good luck with your car

Probably a little of both. Actually, previous owner did the wiring harness, and I bought the car knowing the head gasket and the Evaporator would need replacing. Price was discounted accordingly. I bought it from an MB dealer that had taken in on trade, and wanted to move it. They gave me a good discount on the head gasket. The evaporator core was done by my independent, again with decent discount, and I gave him plenty of time to do it. The reason I like this one is that the interior is perfect, not even a crease in the front seat leather, the exterior is near perfect, and there is absolutely no rust. Given all of this, I don't really have a lot of money in the car and hope to have it around for quite a while. My independent has been all over the car and says there is nothing else needed. Certainly would be hard to replace at anything near the $$ I have in it for anything better (IMHO) - and in this case, I know the big stuff is done, and was done right.