"Symptoms of Failure. [Tips from Marc] The car starts fine and will run for 2 miles and then lose power. It never stalls just won't move. If I shut it off and immediately restart it, it will run fine again for another 2 miles and so on and so on. When it runs fine, with a timing light hooked up on acceleration the timing will retard 1 or 2 degrees before it advances. If I check it when the problem is occuring it will retard 6 or 8 degrees before it tries to advance. Solution: new knock sensor. [Other symptoms] Retarded timing, acting as though no fuel is reaching the engine."

Have you replaced knock sensor? May be intermittant.