Originally Posted by z_diver
If I remember correctly the symptom started directly after a tune up. I took it a independent shop and they did a tune-up while replacing the water pump about a year and a half ago. At the time I was so happy to get the work done for a reasonable price, I didn't care about the hard starting. They attributed it to cleaning the throttle body which I had asked for over there slight hesitance. Would cleaning the throttle body with carb cleaner actually cause something like that?
As far as running flawlessly, it idles nice and has no hesitation when I step on the gas but it is not nearly as powerful as a 300E I had. I feel like it's lagging a bit even for the smaller motor.
As far as tune-up goes, maybe not a full tune-up but I did change plugs recently but not the wires. Would you think i should change those?
Without knowing how they cleaned the throttle body it's hard to speculate. JMHO but I don't think I'd have accepted the car that way, irrespective of price; in this case it sounds like there might have been something they did and now you're left figuring out (1) what that is and (2) how to fix it.
The wires, at almost 20 years old and 150,000 miles, are certainly due for replacement. Simply disturbing them by changing the plugs could trigger a problem, but that's just the nature of things. That may not be related to the current issue, but it's time and should be eliminated as a potential cause, if nothing else.
Re: the throttle body, if all they did was blast carb cleaner down the throat of the TB then that's not ideal. Sometimes that can wash the gum and other gunk into little passages, sensors and the like and that can lead to problems. (We recently did this on a relative's Nissan V6, we were careful to open the plate and put a rag in behind it to catch the crud, you'd be shocked how much builds up in there.) Also, depending on the chemicals used it can also exacerbate a small vacuum leak downstream, which would explain hard starting, but would probably be noticeable at idle, if not otherwise.
Start with the wires, and we'll have Ron move this over to the W124 forum where you hopefully can get more pointed help from your car's peers.
Take care and enjoy the ride,