WASHINGTON (Oct. 7)—The National Highway Traffic Safety Administration has upgraded an existing investigation of tire valve stems on Ford pickup trucks and vans. So far NHTSA knows of 1,133 complaints about the rubber valve stems, including 1,085 reported directly to Ford Motor Co. The stems popped completely out of the tires in more than 450 cases, the agency said, and four such incidents resulted in crashes. Ford declined comment, except to say it is cooperating with NHTSA. Some 629,636 F-series pickups and 249,467 E-series vans are involved in the investigation, the agency said.