My dad's 99 Nissan Quest is experiencing stalling and hesitation problems, mostly during warm-up from a cold start, but it has happened when warm as well. Most of the description of the problem is from my dad, but I did experience some of it first hand, so I'll describe what I noticed.
Overall, acceleration seems more sluggish than it used to be. In fact, I would even go so far as to say it has suffered a very gradual deterioration of acceleration over the years, but now it is very pronounced. Either a standing start, or very low speed rolling start, under light to moderate acceleration, the vehicle often feels as it's going to stall before picking up. On some occasions (not when I was driving), the vehicle actually has stalled.
It has been to an independant mechanic twice for the same problem - the first time, a test drive revealed "nothing wrong" to the mechanic. The second time, some adjustments were done (I wish I knew more than that, but my dad is helplessly non-technical and wouldn't be able to repeat what the mechanic said). This seems to have reduced the severity/frequency of the problem, though it did stall again once.
Any clues which direction the mechanic should be focusing his trouble-shooting towards?