Just now found out what is an issue with my project Arduino car!
It appeared to be I overestimated the capabilities of L293D controller chip. Let me explain...
According to a data-sheet, L293D can handle maximum current draw of 600mA. The motor used in my car has 5AM at free run and 17.2!!! at stall. Woooooooow!
You may ask: hey Nick, what is "free run" and "stall"? This is something I learned recently: motor has two current draw types: when it has no load (nothing stops it, it just runs on full speed in the air for instance) which is free run, and when it has load enough for it to completely stop (when you use a motor in RC car, and then step on it, making it not be able to move) which is stall.
So, the idea here is that I was trying to use L293D chip for purpose which requires 8X times more current just for free run. Crazy, right?
Fortunately, I found alternative, which is BTS7960 43A H-Bridge PWM and fully compatible with Arduino (will see if I can hook it to Raspberry Pi in future).
I'm glad I didn't completely burned all my L293D chips, which means I can try to use a lower current motor just to test steering, and then migrate to BTS7960 bridge once it arrives.
Mystery solved 🕵🏻♂️