Dieseling Problem

[BigRed]

I'm having a problem with my truck dieseling after I shut it off. I seems to do it more when it is hot. I also noticed that the idle is kinda high after I put it into park and about to shut it down. It's not high when I first start it up. If the AC is on when I shut it down, the dieseling doesn't happen. So, it seems like the dieseling always happens when the idle is higher.

What can I check out to fix this problem? If I remember right, overheating is one reason for dieseling, however I'm only running at about 190 F.

By the way, my truck is a 1986 Suburban, 350, quadrajet, stock HEI, 700r4.

Thanks!