Let me start by saying that I am not very mechanically inclined; I am, however, trying to learn since I love my Volvo. It is a 1979 244 DL. A while ago I noticed a bit of lag in acceleration, which gradually worsened to become a violent, jerking motion which seemed to be from intermitent fuel getting to the engine when it is under a load. The engine will hold an idle, so I don't suspect a vaccum leak. I checked the spark plugs, replaced the distributor cap and rotor, replaced the fuel filter, cleaned the throttle body and checked for external fuel leaks. Nothing seems to make a difference.
Also, the main pump is making a loud buzzing sound. I checked the tank pump, but it seems to be running fine. Could it possibly be from my fuel pressure being out of adjustment? If so, how do I adjust it? What about a possible leak inside the fuel tank between the pump and the top of the tank? Any other ideas would be GREATLY appreciated. I would love to hear from anyone who has experienced a similar problem and was able to fix it. I love my car and I want to get it back on the road ASAP! Thanks!