2005 monte carlo seems to run rough / misfire when warm.

There are several potential issues that could be causing your 2005 Chevy Monte Carlo to spit and sputter while driving. Here are a few possibilities:

1. Fuel delivery issues: If your engine is not receiving the correct amount of fuel or air, it can cause hesitation or rough idling. This could be due to a clogged fuel filter, a malfunctioning fuel pump, or a problem with the air intake system.
2. Ignition system issues: A faulty spark plug, ignition coil, or other component of the ignition system can cause misfires, which can make the engine hesitate or sputter.
3. Emissions system issues: Your vehicle's emissions system is designed to reduce harmful pollutants in the exhaust. A malfunctioning component of this system, such as the oxygen sensor, can cause the engine to run poorly.
4. Electrical issues: A damaged or worn electrical component, such as a sensor or relay, can cause the engine to run rough or stall.
5. Transmission issues: If your vehicle is experiencing transmission problems, such as slipping or shifting issues, it can cause the engine to hesitate or sputter.

To determine the exact cause of the problem, it's best to have your vehicle diagnosed by a certified mechanic. They can perform a diagnostic scan to check for any error codes or issues with the engine, transmission, or emissions system.

injectors

If the code is 301 it means there is no power from that cylinder. It could be a problem with the ignition, fuel injector, or something mechanical.

temp sensor acts as a choke...works ok after warms up

temp coolant sensor maybe.

Check the thermostat, if it isn't opening when engine warms up, the coolant in the engine will overheat and make pressure in the cooling system but the fluid in the radiator will still be cold.

I would look inside your distributor cap for cracks or debris. This is the genneral cause of a misfire. However, if the misfire is "rythmic" as in a timed pop pop pop, than you have a collapsed lifter or a bent pushrod. Thank you, Dana

change the air flow meter.

I had this same problem on my 2005 monte carlo, took mechanic a while to figure out it was the idle air control valve. They also replace the idle air control motor.

The ck engine light should not be ignored, what sensor was shown to be bad ? Have it scanned again and replace the sensor that is bad if it still runs rough you might want to consider a tune up. Plugs, wires, fuel and air filter's and clean the throttle body with some gumout. It could also be the IAC motor Idle Air Control. Good Luck