O2 Sensor voltage spike

Hi everyone,

I have been diagnosing this car for a few days now and think I am onto something.
It started out with the check engine light on giving a P0171 - Open loop fault.

Freeze frame data: 
800 rpm
stft 0
ltft 25

When I look at the sensor data, I can see the car going into closed loop way before the o2 sensor is heated up and reporting voltage. So the stft is always gradually rising to 25%, fuel status gives and open loop fault and stft returns to 0% again and starts slowly rising again. This happens about 4 or 5 times until the o2 starts giving normal values and then the fuel trims return close to 0 and all is fine!

What I did notice is a small voltage spike from the o2 when cranking the car, I am 99% sure that the car goes into closed loop because of this voltage spike!! A few seconds after the spike, fuel system status changes to closed loop and stays there...
This morning I tested this by unplugging the o2 when starting up; then plugging it in after a minute and then the car stays in open loop until the o2 reports voltage and all is perfect.

I added a link to the sceenshot of the spike
What are your thoughts about this?

Thanks!

open loop fault indicates you have a problem with your upstream oxygen sensor or sensors, as the case may be.

watch the coolant temp sensor for spikes also , when does it go into close loop