Ive got an 01 blazer zr2 with a 6 inch suspension and 33s.
Ive only had it about a month.
The problem Im having is that when in park the rpms fall down to about 700 and then bounce back up to 900 then slowly go back to 8 for a few seconds and this repeats over and over. Seems smooth, I don't think it misfires at all. Ive actually had people ask me if i was playing with the throttle while I was sitting there.
Also in drive its only at about 500-600 at a stop. I don't know if that is normal or not.

 

Have you checked for vacuum leaks?

Has the maintenance been kept up on the truck?

 

No I havent checked for vacuum leaks yet, i don't really know where to start. I was thinking tps right away but i dont want to just throw parts at my truck because that gets expensive.

And Im finding out as I go and check other things that the maintenance on this was NOT kept up practically at all.