Have a Hyundai Santa Fe 2007 2.0Ltr CDi With a miss in the engine, No 4 piston melted, My problem is i can't find what caused the piston to melt, tested the injectors and they are fine,all delivering the same amount of fuel at different revs and pressure, turbo ok, [ engine didn't rev up on its own ]inlet manifold a bit dirty, [egr] no sign of engine overheating,any ideas ?