Rough idle on a 3.9

[barnfindseries3ffr]

Ok so my RRC 3.9 is in relative great condition, only issue I am having is that it will stall on idle and hesitate if left to it.
On normal acceleration it feels ok, I've changed the air intake today, so crossed that off the list. Next is the plugs, then cap and leads and coil.
Is there anything that jumps out to those familiar with the 3.9? Otherwise it is a pretty sweet sounding engine besides the 260k on it🤔

[bee utey]

Check that the fuel pressure regulator isn't dribbling fuel into the inlet manifold via its vacuum hose.

[barnfindseries3ffr]

Ahh yes, I had a quick look at the hoses around the intake plenum just before I walked away this afternoon and thought that it would be wise to check out the leaking of hoses and plenum bolts.
Thanks for your input bee utey 👍

[PhilipA]

IMHO , the most common causes are
1 a dirty throttle butterfly and surrounds. Get a rag in there and clean it all up.
2 a stuffed Inlet Air Valve
3 If someone has stuffed around with it, after cleaning the throttle butterfly, check that the kerb idle is at about 550-600RPM. To do this you have to block off the IAV at both ends and of course the hole in the manifold( with Duct tape). You then move the little screw above the butterfly up to increase and down to decrease.