a good code reader would maybe help with your fault but things to check would be heater plug operation and the plugs themselves,under the manifold on the n/s of the engine,dual mass flywheels causing crank sensor faults,fuel system for drawing air,check pipes/unions etc,also check for water/contamination in the fuel filter,good luck
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix vans.