Long (but I think interesting and informative) story followed by pertinent
questions.

One day here in California, I start my 2002 Altima 3.5 with 42K miles on it
(which I love and has never given me a problem before). The "Service Engine
Soon" light comes on and even though the engine starts fine, I can't get it
above 1100rpms no matter how far I push the accelerator pedal. I turn the
engine off, restart and all is fine, but of course the SES light is still
on.  The next morning, it turns over fine and starts, but dies after a
second.  I try this about 20 times, same result.  Finally it starts, but
same no rpms problem.  After a few more stop/restart trys, it roars to
life. Once its running with full rpms available, there is never a problem.

Of course by now, even dumb me realized I ought to have this checked out.
Its Friday, I take it to the dealer on my way to work. He can't take me
that day, and gives me an appointment for Monday morning. I decide to drive
it over the weekend and take my chances. Most times, it starts right up,
but maybe once a day, a have to go through the same start-die, start no
rpms, start fine procedure.

I decided I ought to do some invesigation of my own to limit the chance of
the dealer ripping me off. First I checked the recalls on this car.  
There's one for the crank position sensor (cps). My symptoms sound just
like that, but mine's already been replaced under the recall, before I had
any problems. I even see that there is a cps recall to fix the first cps
recall, but mine was done after the second one, so should be ok.  Then, I
rented a OBD II code reader at Auto Zone (free, just make a $170 security
deposit). The code came back P1121 Fuel/Metering.  This is an OEM code, so
there's no specific definition.  I searched the web on the sites that
supposedly have all of the Nissan OEM codes, but none of them seem to know
P1121.

I bring it to the dealer 7:30 am Monday morning. I chose a dealer because
even though I'm passed my 36K mile basic warranty, I was pretty sure the
problem ought to be covered under California's 50K mile "Emissions Defect
Warranty." Its my understanding after reading my warranty book, and studing
the California Air Resources Board (CARB) website, and having similar
experinces with other cars (see the p.s. below about the attempted rip off
at a Ford dealer on a similar issue), that pretty much anything that sets
off the Service Engine Soon or Check Engine Light is covered, by law, under
the California's 50K mile Emissions Defect Warranty.

The service rep at the dealer writes up my ticket and says they'll check it
out and let me know. I told him the symptoms, but I didn't let him know
about the results of my code check.  He puts an initial estimate of $85 for
the diagnosis. I tell him that I'm pretty sure that becasue of the SES
light, it ought to be covered under the Emissions Defect Warranty. He says
maybe, but many things aren't cover under that, including sensors; that it
has to be specifically mentioned, such as a catalyst. I tell him he's
wrong, that anything connected to the ECM or monitored by it, including
sensors, are covered.  He says they'll check it out and he'll call me.  
With that, I walk away to my ride, my back to him, muttering under my
breath my opinion of his viewpoint, complete with a few choice profanities.

4:00 pm and still no word on my car, so I call the service rep.  They can't
find him, so I leave a voice mail "What's up with my car."  Service rep
calls me back about 4:30 pm.  Good news, bad news. Good news, the problem
is indeed covered under the Emissions Defect Warranty. Bad news, they don't
have the part. They would be happy to have me leave the car there until the
get it (great, either no car or $35+/day in car rental fees) or pick-it up
and bring it back when they do have the part, and of course take my chances
with the no start issues until then.

I decide to pick up my car and take my chances, especially since I'm going
on vacation in a week and won't need it. When I get to the dealer, the
service rep explains that the problem is the "throttle chamber." I'm not
sure if this is a sensor or what, but he shows it to me.  Its on the air
intake duct about half way between the air filter and the engine. It has a
big electrical connector on it.  I ask him if this is something like a Mass
Air Flow sensor, but he says no, its different, but can't really tell me
what it does. He says he's seen this problem on few Nissan V6s and wonders
if there might be a defect (no recall on it, he checked it and so did I).
He also apologized if he seemed rude earlier in the morning (he must have
heard my muttering), but according to him, indeed some sensors (earlier he
said it was all) aren't covered under the Emissions Defect Warranty, such
as the O2 sensor. Since mine was covered, I chose not to debate the point
with him. When I got in the car, I noticed one interesting thing.  There
was a little slip of paper, like you get from a cash register. It was the
printed test results from the code scan the dealer did. It has the date and  
the title "SELF-DIAG RESULTS." It says "ETC ACTR" and "[P1121]" the same
code I got.  I'm guessing ETC ACTR stands for Electronic Throttle Control
Actuator, but that is indeed a pure guess. My invoice from the cashier says
"CAUSE  THROTTLE CHAMBER DEFECTIVE" and "CORRECTION  SPECIAL ORDER THROTTLE
CHAMBER."

Anyway, it now the next Saturday, five days later. Over the last week, the
no start problem has periodically popped up.  It most cases its just an
annoyance because the car starts right up after a few trys.  But one
evening, it took me almost a half an hour to get going and I was pissed.  
Having not heard anything for a week, I called the service rep Friday
afternoon to see about my part. "Oh, they haven't emailed me, so that means
the part is not in; I'll call you when it is." Tommorow I leave on vacation
for a week, so lets hope they use that week to get their supply chain
moving.

So here are my questions:

1. Anyone else experience a no start, start but no rpms problem like this?
If so, what was it? Is this problem wide-spread? Maybe there should be  
recall on it.

2. Does anyone know what Nissan OEM OBDII code P1121 specifically refers to
and why no one else does. What does ETC ACTR describe?

3. What does the Throttle Chamber do?

4. Am I right about California's 50K mile Emissions Defect Warranty? Here's
a quote from the CARB website "California's emission warranty requires the
vehicle manufacturer to repair under warranty any problem that the OBD II
system detects if the vehicle is less than three years old and has less
than 50,000 miles."  Another quote: "including any defect...which would
cause the vehicle's on-board diagnostic malfunction indicator to
illuminate...."

5. (not really a question) Please educate everyone you know about all of
their rights under the emissions warrantys. In addition to the 36month 50K
mile California emissions warranty, there is a Federal equivalent. Its
limited to 36k miles, so it wouldn't help me.  There is also a Calfornia 7
year 70K mile warranty on "major" emission items like fuel tanks, intake
and exhaus manifolds. The ECM and Catalyst are covered for 8 years or 80K
miles under federal law.

P.S.
I also own Ford Explorer.  It was runing real rough one day. My wife took
it to the Ford dealer.  Dearler tells my wife, bad fuel injector, normally
lots of money, but Ford has a "special program." Ford will pay for 2/3 of
the fix; my cost only $200. I tell wife I'll call dealer.  I call dealer
and tell him fuel injectors are covered under emissions warranty (car had
just under 50K miles). He says, have to check "this car." (Note, the
emission warranty is the same for every car). He calls me back.  Yes its
covered, no charge. Moral of the story, know your rights! Also, aren't
these guys scum. The dealer knew full well it was covered. But they won't
tell you unless you tell them.