OWNER WAS DRIVING THE VOLKSWAGEN AND SMELLED A WEIRD ODOR, SO HE PULLED OVER TO THE SIDE OF THE ROAD. HE OPENED THE HOOD AND LOOKED TOWARD THE BACK OF THE ENGINE AND OBSERVED SMOKE AND SMELLED SOMETHING BURNING. HE STATED HE OBSERVED FIRE FROM THE BOTTOM PART OF A WIRE HARNESS. A SUBSEQUENT EXAMINATION REVEALED THE SPARK PLUGS SHOWED A SLIGHTLY RICH FUEL/AIR MIXTURE IN THE CYLINDERS, RESULTING IN POSSIBLE OVERHEATED EXHAUST COMPONENTS. CAUSE OF FIRE UNDETERMINED. *NM