Trying to help disabled neighbor. He takes me for a ride. After about 4 miles, it acts like it is starving for gas. Surges, chokes, surges, chokes. He changed the fuel filter. I poured a bottle of Dry Gas/ Injector Cleaner in the full gas tank. No change. He lets it sit for a couple of hours and it runs fine for awhile and then the problem reoccurrs. Also, we removed the gas tank lid, and the problem continues. Where should I start? Thanks for any help. Joe