I don't know about your exact model, but possible the ignition timing is a
little too far advanced

Retarded timing makes a car start easier from cold and run up hills etc

Advanced timing is needed for good higher speed running

Sometimes if the timing is too far advanced you can hear a
"pinging/knocking" if for instance accelerating hard in top gear, especially
if going up a hill

This simple test, is not so easy to do in an auto gbox car (as it will
change down a gear on you)

Assuming your car has normal type ignition points (and NOT pointless
ignition) then fitting new points, and setting their gap correctly, can have
the effect of slightly setting the timing wrong (compared to what it was
before, with the old points installed)

One "fix" is to slightly set the points "wrong" (a little tiny bit less or
more than the recommended gap)

However this upsets...if I'm right, the "dwell angle" so can only be used to
a limited degree.

The proper fix for wrong timing is to correct the timing.  Some old English
cars had a "micrometer" adjustment using a finger turned knurled nut on the
distributor (I used to have my 1959 Vanguard set, so that for cold Winter
starts with the handcrank, I'd adjust the knurled nut all the way to
"Retard", then wind it back all the way to "Advance" once the engine
started.....I never once had any bad experiences with the crank starting
handle ! (Heard stories of broken jaws and thumbs ripped off)

Most cars nowadays no longer have that fine "micrometer" adjustment. It's
necessary to loosen off the 2 bolts securing the base of the distributor and
twist the body of it VERY GENTLY a tiny bit one way or the other

Take the dist cap off and see which way the rotor top turns while having a
friend turn the starter momentarily

Now you can visualise "if I turn the dizzy THIS way, the spark happens
EARLIER (ie advanced) and if I turn the dizzy This way, the spark happens
later, ie Retarded

I notice that my Nissan, the rotation of the distributor rotor is the
opposite to what all the English cars I've had is

If possible, use a felt pen or something to mark the dizzy body-base and
mounting base before you try moving them, that way you can always return it
if no improvement is made

Remember that you only want to turn the dizzy a tiny bit (usually it's a bit
stiff and then suddenly it turns a lot and you have to turn it back some)

DO NOT LIFT THE DIZZY UP or the drive thingy underneath will get all out of
kilter etc etc, ya don't wanna go there

When my Nissan came back from the Datsun specialist after having some major
engine work done (new timing chain and gears, I's thrilled with their work
generally) but I noticed when going up a decent hill that it "pinged" very
badly

After I got home, I retarded the timing very slightly, the pinging on hills
is now "almost eliminated" (which is generally considered to be the right
effect) and the car's been going great ever since

cheers
Catherine
Rural Western Australia

Mmm on re-reading you post it seems as if your model of car probably doesn't
have contact-breaker-points and as such you wouldn't have changed them and
upset the timing that way

I dunno exactly what your electronic engine management system does, and how
much it tests for. Perhaps the "check engine" light would react to bad
timing and perhaps it wouldn't

Sorry I can't be of much help, but hopefully someone with more knowledge of
your actual model will reply

cheers

You've done all you can besides finding a reputable repair facility and paying
them to fix the problem.

Does the hesitation seem to happen when the gas pedal is in a certain
position? (Light acceleration vs full throttle)
When at cruising speed does the tranny seem to shift in and out of lockup?
If so I would check / replace the TPS (Throttle Position Sensor)

It's fixed!

Turns out it was the timing.  The timing was set to 5 degrees Above
Top Dead Center and I found the factory setting is supposed to be 10
degrees Below Top Dead Center on the 1.6L 4cyl.  The following
websites helped to figure out how to check and adjust the timing:

http://autorepair.about.com/library/illustrations/bl676a-lib.htm
http://www.sentra.net/tech/maintenance.php?S=5d14ba55dfd0d5df5677b3101846adaa#minor

Thank you to everyone who provided suggestions and advice.  I really
appreciate your help.

Thanks,

Brian