THE PLT WAS ON A NIGHT X-COUNTRY FLT TO POSITION THE ACFT AT DEFIANCE, OH. IN THE VICINITY OF MALINTA, OH. SEVERAL WITNESSES HEARD AND/OR OBSERVED THE ACFT CIRCLING FOR APRX 5 TO 10 MIN. ABOUT 1/2 OF THOSE WHO HEARD THE ENG SOUNDS SAIDTHE ENGS WERE SPUTTERING OFF & ON. THE OTHERS RECALLED HEARING THE ENG INCREASE & DECREASE IN POWER SEVERAL TIMES. ONE WITNESS STATED THAT THE ENGS SEEMED TO LOSE POWER DURING DESCENTS, BUT WOULD REGAIN POWER AS THE ACFT ENTERED A CLIMB. THIS HAPPENED TWICE. ON THE 3RD DESCENT, THE ACFT CRASHED APRX 2 MI FROM THE HENRY ARPT. THE ARPT WAS EQUIPPED WITH RADIO ACTIVATED RWY LIGHTS. THE IMPACT OCCURRED IN A 19 DEG DESCENT, SLIGHTLY RIGHT WING LOW. AN EXAM OF THE WRECKAGE WAS MADE, BUT NO PREIMPACT PART FAILURE OR MALFUNCTION WAS FOUND. REPORTEDLY, THE ACFT HAD DEPARTED DETROIT, MI WITH 565 LBS & WOULD HAVE USED AN ESTIMATED 300 LBS, ENROUTE TO CLEVELAND & ANOTHER 300 LBS TO THE ACCIDENT SITE. THE OPERATOR ESTIMATED IT LEFT CLEVELAND WITH 70 GAL. AT 0620 EDT ON 10/3/83, THE PLT GOT A WX BRIEF FOR PREV FLT.