I've been having a weird problem with my '95.. its a 4.3 Vortec Vin W before i get started, the problem i'm having is while the truck is idling it runs for a minute or so then the RPMs increase for a few seconds then it drops back down to normal idle then this repeats almost like clockwork. I have no codes in memory or anything of the sort, and have talked to quite a few master Techs and they are clueless, so anyone has any ideas what is going on with my truck?

 

Have you checked or cleaned IAC?