V8 Auto Issue Wont run in D or R

Hope someone can point me the right direction. Just got the V8 3.9 EFI up and running again after several weeks, charged battery, new dizzy cap, rotor & leads (Genuine LR - been the naff cheap route before). Few squirts of carb cleaner in the filter and away it went.

Start and ticks over fine but as soon as I select R or D, even N it dies. Only way to get it to drive is left foot on break and keep the revs up, but just wont tick over at junbctions etc.when in D.
Worked fine before the battery went flat and left to stand for 6 weeks.

I'm sure its something simple, but don't know where to look.
Thanks

Thanks I can drive it, just have to hold the foot brake and build up the revs before shifting into drive. May be a connection to H/L as I was lubing the linkage and shifting it to loosen up.

Definately something stoppingt tickover/run when shifted out of park

is the fluid level correct?(needs to be bang on, not over or under)

Thanks will check, was working fine and will drive but only if I hold it on the brake to build the revs up and off she goes. Could this be due to low fluid.

I've suffered similar in me off roader 3.9efi. Would echo whats been said about fluid level. has to be spot on.
Also, check the idle stepper. Mine had air leak getting in by a dodgy gasket seal. just a quick remove, clean up and refit with new gasket solved issue. Now only occasionally bad when in lo ratio...but think i thats other things
Crap/dirty plenum chamber can affect running which only becomes more evident when the engine gets puts under slight load....my old 3.5efi had loads of crap in the intake n plenum. cleaning up helped big time.

Whats it like if you turn the idle running speed up slightly?

stepper needs cleaning or base idle needs re-setting

Pulled the stepper, was sooty but not full of carbon, cleaned it with carb cleaner. Is the plunger supposed to pull up and down by hand, it hardly moves. I also read that the plunger should move with inginition switched on, didn't. While I was at it I pulled the hose from AFM to plenum and cleaned up the throttle plate and surrounding area with carb cleaner. Now doesn't start at all, will check for a spark tomorrow. tks