My 96 Max stalls when engine is cold!!!
It will keep doing it while I'm slowing down or stopped only until the temp arrow in near the middle of the gauge.
After a very-very long worm-up - no problem.
So, definitely temperature-related

Cleaned TB and Airflow sensor. (got a little better now, but problem is still here)

Codes:
1. P0125 - Insufficient coolant temp for closed loop fuel control
2. P0155 - 02 Heater Circuit (Bank 2, sensor 1)

Don't know which one I should troubleshoot first and don't know where those sensors are located.

Any link or directions are highly appreciated.

 

Unlikely to be the O2 sensor. I would guess that your temperature sensor that connects to the ECU has stopped working. ECU doesn't realize that engine is cold, so doesn't provide enough fuel at idle and car stalls. Do a search for that sensor (may be called ECT sensor). It's at the right front corner of the engine as you are looking at it from the front; undeer a couple of things and in a coolant pipe.

The Bank 2, Sensor 1 O2 sensor is the one at the front in the exhaust manifold between engine and radiator. Easiest one to get to and change. Good luck.

 

Also, if there just worked on the upper intake manifold or anything after the Mass air flow sensor. you may want to check for any un-metered air getting by.

 

Do a search for that sensor (may be called ECT sensor). It's at the right front corner of the engine as you are looking at it from the front; undeer a couple of things and in a coolant pipe.


Thank you very much for your input.

I found two things:
One is called Coolant Temperature Sensor ,
Another one is called Engine Temperature Sensor

Which one do you think it is

 

Just found a little crack in the radiator.
It is in that short plastic vertical tube, right below the cap. Very small amount of fluid is getting out when it boiling.
I don't think this is what causing the issue though. - Wanted to bring it up just in case

 

If anything, this would more likely cause an overheat condition as the cooling system will not pressurize.

 

If you are loosing coolant through that crack, the sensors may be getting a false reading due to a pocket of trapped air in the coolant pipe. How is your coolant level in the radiator, not the reservoir?
The O2 heater circuit could be from a bad fuse on the O2 heater circuit. Or the heater element in the sensor itself may be bad.

 

I have the same concern (that is why I mentioned that): maybe, if there isn't enough coolant - the coolant temperature sensor doesn't have the proper readings and thus causing the problem.
Also, it could trigger the fans to turn on prematurely, what do you think?

I'm going to fill up the radiator (and the reservoir) to the top tonight and will see if the car will stall when it's full.
(it boils out through that crack on top though )