he is going to have to get it professionally cleaned. call around to local car detailing places. they should have powerful enough cleaner to get the smell out, and make sure you price check! we all need to save money these days!!!
Some cats like to 'spray' and mark their territory. Don't know if this is the case, but, good luck. Sorry to hear...I'll ttyl...(Sister on line). (HUGS)
that is gross. get a cleaner that is designed to remove pet odors. hopefully that will help, but in the summer heat, its going to be difficult to remove a smell like that. good luck.
