Problems with Voyager 2001

Tango Un Voyager 2001, until recently everything is working well, but suddenly the rpm began to lower the point of almost apo. When it is in D without walking the rpm fall to 1300 approx the truck trembles a lot. It was already made a change of buijias, injector cleaning change of spark plug cables (complete tuning) and remains the same, which can be what is happening? thank you...

Acceleration sensors such as the TPS sensor or the AIS or valve jack engine that name it
or can be the sequence of some coorient lenes of the crankshaft and camshaft motor are already the only one they fail if they fail if they fail is the only shape that the engine is turned off and cause that it works