A Coralville man is recovering from his injuries after a leaking L-P gas tank exploded yesterday in the back seat of his car. Kenny Grantham was inside his car when the L-P tank blew up and had just gotten out when a second tank in the trunk exploded. Grantham was treated and released from University Hospitals in Iowa City. Neighbor Nathan Raffensperger heard the first blast, grabbed his video camera and caught the second one on tape as Grantham fled. He says the explosion happened in a busy residential neighborhood just a few blocks from Coral Ridge Mall.Investigators think the first blast was sparked when Grantham turned the ignition key. A third propane tank stored in the trunk did not explode.