E300 with M103, need helpful ideas

[junqueyardjim]

My 86 300E runs super. It is the 89 engine I bought from John Heff about 4 years ago. This week I had my first issue with it. I drove it to my bus park to get my school bus. Parked the car at about 6:30 AM, temp about 28 degrees. Came back 2 hours later, temp is up to 36 degrees outside, car started instantly but would only run up to 1500 rpm. In gear with manual transmission, it would not pull but if I got off the throttle, it idled very rough. I tried to keep it running, it never did stall but came close. I kept on pumping the accelerator maybe for 30 seconds, maybe more, it was running rough and then instantly, maybe after a minute of fussing with it, it cleared up and ran great. Now today, leaving the bus park it did the same thing, but it cleared up in perhaps 30 seconds, then I made two short stops about 10 or 15 minutes each, (engine now is fully warmed up) and each time I had to wait and pump the accelerator 10 to 15 times I think in 15 to 20 seconds, while it acts up and really runs terrible. Then instantly it clears up and every thing is fine. Anybody have a good idea for me? I am very interested in correcting this problem.