Truck cuts off when put in gear

Does it run rough at hot idle ? How many miles ? Any recent work done on engine ?

If your mechanics say the mass air flow sensor, fuel pump and fuel filter is good then check your intake Manifold Gasket. It is a hard 1/4 inch thick plastic gasket that cracks frequently and causes sputtering when letting off your gas pedal and eventually lead to stalling at red lights and stop signs if cracked bad enough.

Any sounds or smells?
Check engine light on?

idle stop screw may be out of adjustment or idle air control not working as it should (iac) valve pass side of tbi slightly to the rear

Most likely a leaking EGR valve... very easy fix!

what are the trouble codes? does it have elec. throttle insdead of cabe

check with timming light to c if jumped timming,it needs to be at least 1000rpms to run right

Its part of the quick warm up gear worked off a switch on the dash its on all the EU models not a jake brake like a truck. Wont come on once the engine is over 55 c . We dont touch em in the UK as they are prone to stick shut !

DOES YOUR TROOPER HAVE A 3.O DOHC TDI ENGINE IF SO WHAT GRADE OF OIL DID YOU USE