After being parked for several hours, I drove off in my 96 Infiniti
I30 (114K), went a few blocks, and the car lurched a few times, then
killed (no idiot lights while running).  I restarted it, and "lurched"
it out of traffic and had it towed home (it was the middle of the
night).  I don't have a regular mechanic that I know and trust here in
Las Vegas, and the next morning I just took the car to an AAA
recommended shop, for what that's worth.  

The mechanic couldn't duplicate the problem, and said the only code
that had come up was the knock sensor code. He said he drove it around
for 40 minutes with no trouble.  So he replaced the fuel filter and
did some "injector/intake TBI" cleaner thing, and said I was good to
go.

I picked up the car this afternoon and drove it around for about 5-10
miles of errands, on and off the freeway, with no problems.   Parked
the car, and then went out for dinner several hours later.  Same
problem again--car started fine, but began to lurch after about a
mile.  I limped it back home.  This time the engine light came on and
stayed on.

So the only pattern I see here, if it means anything, is that both
times the problem happened at night--after the car had been sitting
for hours.  (It's been around 100 degrees here in the daytime lately).
When I picked the car up at the shop today, it had been sitting for
two days, and it ran fine.

Any ideas (other than maybe looking for another mechanic)?
---
Steve Green