How can you get the co2 down on a 92 bonneville? already replaced o2 sensor, fuel filter, catallytic converter. run several injector cleaners.

Clean the idle air valve with carb cleaner. Replace O2 sensors. Your upper O2 sensor is weak causing a lean fuel mixture after it is full warmed up and at low rpms. Say less than 900. You can run a scanning tool that will check your O2 sensors to see if it is bouncing voltages of about 0.5 to 5.0v several times per second to adjust fuel injector output. If that's not it it may be fuel reg, filters, fuel pump, etc. 1st question you need to ask yourself is, "am I up to date on all maintenance". This includes O2 sensors.

run the fault codes to check for sensor problems that is causing this result.

No the stalling is caused by something else like a dirty fuel filter of bad fuel pressure due to a worn fuel pump. With a bad O2 and MAF sensor the ECM will go a on open loop mose for those sensors causing bad performance and gasmileage. Replace the O2 sensor and try cleaning the MAF with MAF cleaner and check the wire harness, look for any damages to the wires and replace if needed. As for the stalling, try replacing the fuel filter first and we can go from there. Keep me posted, be glad to help get your car running 100% and save you some money the same time.

What's missing when it dies ? Fuel , spark ? Why even mention closed loop , that has no bearing on it . When the vehicle get's hot ,a sensor is shorting out internally causing it to die. Then when it cools down it starts again, correct ? Pull plug wires off one of the coils an turn the key to start , do you see spark ? Put a fuel pressure gauge on the vehicle an see if there is pressure . Or find yourself a guy like this
How to test GM 3 wire crank sensor hall effect type

Here is some info for you to read, besides me explaining what ppm is, i also gave you some info of how to solve this, Ain't that special LOL. Mike

Overall Result: PASS or FAIL. A vehicle with a properly operating engine and catalytic converter will have very low HC and CO readings. However as a vehicle ages the HC and CO emissions will increase and may become erratic. As a vehicle ages it becomes increasingly important to be sure that the engine and converter are fully warmed up before the test to have the best chance of passing the test.

HC (PPM): The parts per million of hydrocarbons (unburned or partially burnt gasoline) in the exhaust.

CO (%): The percentage of the exhaust that is carbon monoxide (CO).

CO +CO2 (%): Complete combustion in the engine or catalytic converter will result in very little carbon monoxide (CO) and a high percentage (up to about 16%) of carbon dioxide (CO2) in the exhaust.

O2 (%): When there is complete combustion in the engine or catalytic converter there is a very little oxygen (O2) in the exhaust. Usually less than one percent. A higher reading indicates a problem with the engine, the exhaust system, the sampling system or the catalytic converter. Vehicles do not pass or fail because of the O2 reading; it is only diagnostic information.

RPM: The engine speed in revolutions per minute (RPM) or N/A.

Cruise Limit: The maximum allowable HC and CO emissions at 2500 rpm. The CO+CO2 (%) must equal or exceed 6. This verifies an adequate sample of the exhaust has been obtained. N/A for O2 and RPM.

Cruise Emissions: The emission readings measured at 2500 rpm.

Cruise Result: PASS, FAIL or N/A.

Idle Limit: The maximum allowable HC or CO emissions at idle. The CO+ CO2 (%) must equal or exceed 6. This verifies an adequate sample of the exhaust has been obtained. N/A for O2 and RPM.



These are the possible problems:

bad o2 sensor
bad EGR valve
bad cat
bad timing
dirty injectors
bad plugs or wires
the less costly fixes include replacement of the o2 sensor and EGR valve i would not clean the EGR I would buy a new one there are very cheap you can pick these up at any local parts store .
also run some injector cleaner through your car at least a full tank of gas and one bottle of injector cleaner should be ran through.
you can also have your timing checked for a relatively low price.
and when you go into to have the vehicle checked make sure the car is been running because your cat convertor has to be warm in order to preform at it peak so do not do it when the car is cold.
all of the above are pretty reasonable fixes the general rule of thumb when you work on your own vehicle is start with the cheapest fix first then go on to the next.

crank position sensor...if the engine will start and run for a second or two then it dies. If, however, you can press and hold the gas pedal slightly and keep the engine going, then I would suspect the IAC-idle air control valve. This can be cleaned with spray carb cleaner.

You haven't tuned anything. Tune-ups went away in 1980 with the introduction of electronics.
Fuel filter -filters fuel
Injector cleaner-waste of money,on some fords, it will remove the coating on pintle and is not recommended
TPS Sensor,was replaced after you tested it ,and found it defective?
Spark Plugs-ever hear of one failing. Never seen one fail in 47 years.

Have you considered the EGR Valve,Vacuum Leaks,Old O2 Sensors,again,test first,then replace,blocked converter?

Sounds like your car needs a tune up.
Need to check your plugs, plug cables and fuel filter.
Also check your O2, CO2 and temperature sensors.
Do you have warning lights or a lot of exhaust smoke?

DTC code P0421 is the O2 sensor that indicates a an issue with the Catalytic Converter. Replace the O2 sensor to the Catalytic Converter "the one after Converter" It's common for the sensor to fail and you can pick one up from Auto Zone and they will have the step by step instructions to replacing the O2 sensor. 
DTC code P0302 Indicates a misfire on cylinder #2. Address the spark plug, spark plug wire, and injector. Look for any damages and try running some fuel injector cleaner through the fuel system to clean out the injectors. 
Good luck and hope this helps. 

There's a lot on any car that can cause loss in power.
A few of them are:
Mass air Flow sensor
Bad O2 sensors
Old oil or sludged oil
Bad Gas
Clogged catalytic converter
Loss of cylinder pressure or compression

I would start with the cheapest tests/fixes first
oil: if you haven't already and don't know the condition of your oil, change it. If your oil has sludge in it then you could have a leacking head gasket.

Next up, If your gas is bad fill the tank about half way and use lucus oil octane booster, and for a second half a tank pour in some seafoam engine cleaner. It will clean your fueling system, injectors, and pistons/chambers.

If those too don't help: get a compression test on the cylinders. Not expensive to have done, but could be expensive to fix if there is something wrong or the compression is leaking.

Next, go to a muffler shop and have your catalytic converter checked. A clogged or bad Catalytic converter may trap exhaust and keep it from exiting your exhaust system.
While your there you can have your O2 sensors checked.

If all of that is fine, replace the O2 sensors and the Mass air flow sensor. These components control the air fuel ratio. If they are going out your engine won't ever get the right amounts of gas and air to run properly.

It's a lot, but my general rule of thumb for trouble shooting any issue with a car is to start with the cheapest fix and work your way up.