it was knocking but iam not sure b/c it will stop it has done this before only once and went away after a day my oil gage inside will bounce all over when i let off the gas please help

Get it checked out asap. The same thing happen to my friends explorer. When he hit 45 mph it started knockin and oil gage started to jump and turned out to be the engine blowin from the guy who sold it to em never had the oil changed so the engine was only running on 4 cylinders and its a v6 so it had no oil pressure at all but this truck also had 190,000 miles and wasnt taken care of. Get it checked out now before its too late. Good luck

Try higher octane fuel.