Here we go again. I've seen many threads in this forum on rough idle and the cure being adjustment of the damper bolt. Also many opinions on which cars have them and which don't. I have a 76, 240D with the Bosch M type pump (pnuematic governor), that has the classic symptoms of rough idle. I have adjusted the valves, installed new timing chain and verified valve timing using valve opening measurement technique, retimed injection pump with low pressure drip method, and installed rebuilt injectors. Car runs great except for the rough idle and there is no excess smoke problems. The only thing I see that resembles what I have read described as the rack damper bolt is a slotted stud with a 17mm (wrench size) nut on it on the end of the pump closest to the firewall. After trying to adjust it clockwise the only thing I could accomplish was to lower the top speed of the engine with a moderate adjustment, and if I went several turns the car would stall. Counterclock wise seemed to raise the engine top speed and started to create some smoke.
Now if anyone is still with me after this long description, can any one tell me where else to look for the damper bolt and how do I properly set the bolt that I did mess with? Any other suggestions if I don't have the rack damper bolt?