I have a 1992 Dodge diesel pickup, 250. Starting several weeks ago, the pickup would run worse and worse every day. It was hard to get the rpm's up to run properly. Tried changing the air filter, the air cleaner, the fuel filter, the transfer pump; nothing has worked! Now the problem is so bad that I can't even get it out of the driveway. I have to keep my foot on the pedal just to get a few hundred rpm's out of it to move it, and it rattles and clanks. On top of that, there is a lot of white smoke. The local Dodge dealer set the timing on the injector pump (or so they said). I've been told that the injector pump needs to be replaced - way expensive!!! Before I go that route, is there something else that could be causing these problems?