I recently bought a 1986 Mercedes Benz 300sdl for $1250. Thereis very little rust and it only has 171k miles. My question is what would cause a slow acceleration from complete stop AND speeding back up from slowing down. Especially from slowing down and speeding back up. this is my first deisel and I do know the acceleration is going to be slower than what im used to, but its so slow that I **** off the people behind me when merging onto the highway. Also the speedometer says it could go as fast as 140mph but the fastest i'm able to go 70-75mph. Any suggestions would be appreciated.

Oh, I have replaced the ait filter and both fuel filters with no improvement. It doesnt overheat, oil pressure is good, very little whitish smoke. There is slight knock when idling but im not sure if that is normal for a deisel. The knock goes away once I accelerate. There is an oil leak but not enough to affect the level on the dipstick. Also a tranny leak somewhere and I had to add little fluid.

 

Try to find the knock, and look for air in the fuel ststem. Leaks are your worst enemy. They cause all sorts of power related problems, loss of power, slow accelleration, hard starting just to name a few. Your knock could be a fuel knock (normal) or it could be a worn injector, or a loose valve wihch would cause slow acceleration. If the fuel knock is extra loud, then there is most likley air in the fuel system.

 

I'll definately check those out. I want to get this problem fixed before I get started on restoring the interior.
Thanks again.