Nissan Repair: 1993 Nissan Quest idling surge, air control valve, vacuum leak

Question
   I have a 1993 Quest.  The transmission was bad, so I replaced it.  Now, when this is started, the idle goes up and down.  Before the trans swap, it idled fine.  The trans came from a 1993 Villager.  Any thoughts?

Answer
Thomas,

It is not the transmission that is the problem.  When the transmission was installed they might have nicked a vacuum line so you have a vacuum leak.  That is one possibility and another is the idle air control valve might have carbon deposits that broke loose with all the activity involved with the transmission removal and installation.