So my truck does the thing where when you start it up again (after stopping at the store for example) it idles at 500 or so RPM. It seems like when I go to start it it just barely starts itself. Once I start going it gets itself back up to a higher idle. Problem then is that the idle jumps around from 750 to about 1100. Another thing is that when I let out the clutch the tachometer falls to about 500 or so RPM then jumps up to wherever it's deciding to idle. ALSO I notice that sometimes especially when revving high the tachometer jumps around a bit. It isn't throwing codes and it's pretty decently maintained. The only things I have left is a new timing belt and PCV valve. I'm at a loss.

 

Could be any number of things really.... I would 1st start by cleaning the grounds to coil and igniter, jumping tach needle is usually associated with that, and could contribute to the jumping idle, then move on to testing your vafm, tps, and start searching for vacuum leaks.