We recently bought a 1995 c250d elegance, we have had the glo plugs replaced, a return valve fitted on fuel line and fuel lines replaced (because idiot past owners were running the car on agricultural diesel and mixing it with diesel oil to hide the colour! ) Even tho this work has been done (and we are treating the tank with redex diesel treatment to remove any residue) the car seems to be 'misfiring' when on the move but not when idling. She needs to be well warmed up before she stops this jumping (a good 15 miles). This jumping seems to occur on the cusp of changing gear, but will do it in every gear. We have considered taking the tank out and cleaning it, but any help/suggestions would be greatfully appreciated! PS when car is in reverse the car makes a knocking noise underneath (roughly in drive-shaft area) HELP!