Model: GC25P-5
Engine: GM G424FE
LP

Our Fork lift runs good for ten minutes or so. It then backfires and has trouble starting after it backfires unless you let it set for twenty or so minutes. If it happens to start after a backfire it usually backfires several times before actually running again. Once you get it running after the backfire the acceleration is really low and it moves very slowly. Eventually, the acceleration will pick up and be back to normal but when you go to park it, it usually backfires once you put it in neutral or remove your foot from the gas pedal. Using the clutch and the gas pedal and keeping your rpm's up usually helps keep it running. Once it sets for an hour or so it usually runs smoothly again until you use it for 10+ minutes. It runs great until it doesn't.

Fixed or Replaced

Spark plugs
Wires
O2 sensor
Propane regulators
Inner Air Filter that was destroyed along with the outer filter.
Fuel leaks after the regulator replacement
Air intake