Things I'd check first... IACV, fuel filter, air filter. Those are the easiest and cheapest. Plugs and wires are always a good thing to keep up with as well. If those relatively easy things don't solve the issue I'd dig deeper.

 

Start with removing the IAC Valve (Stepper Motor) and cleaning the Pintle Tip, and also the female cup end where it seats with some throttle body cleaner. Go easy removing the valve so you don't kill the gasket, and/or have a gasket (ERR3359) on hand ready to go.
If the IACV is old most likely it's time to replace it, but clean it first and see if things improve.

 

 

if everything mentioned above checks out, I would suggest you go back in and check the intake manifold bolts, if they are slightly loose , that may be a source of a vac leak.....speaking from experience

 

It also might simply be that the IACV is dying. Happened to me.
https://landroverforums.com/forum/di...pensive-81775/

 

 

Don't use the O-ring. the tabs will eventually bend as the valve base does not sit flat on the throttle body. Use the flat gasket and it will last.