Ok, when my truck is sitting at idle, something clicks on and off on the engine... It will be sitting there and I hear a click and then the idle gets a bit rougher, then a click again about 30 seconds later and it's smooth, then a click about 30 seconds later and it's rough and so on and so on and so on... And no my A/C is not on /forums/images/graemlins/tongue.gif. Anyway, what would this be and whatever it is should it be doing it this often? Oh yeah, 96 vortec 454. All my engine building experience is for pre-efi stuff so I dunno what they have stuck on these things... It sounds like a relay clicking on and off.