I haven't checked the condition of the throttle body. I will get it checked thanks for pointing it out. I have been doing a lot of observation and since last 2 weeks, I have been parking on an inclined surface and every time I would park on that spot and leave the car for few hours, it is certain that the hard start will occur.

The parking is such a way that the rear side of the car stays higher by by an inclination degree of 45 degrees. This happened every time I parked in that inclined surface. Does this tell you something? It happens regardless if the fuel tank is low or high. The number of cranks is the highest on the hard starts there.

 

Based on your description of the parking spot, if the condition occurred with the fuel low in the tank, then I could understand and say it may be normal.
But if it does it with the tank full, or even half full, then it shouldn't make a difference.
Also in the IS the fuel pump is towards the front of the tank anyways, so with the rear higher it will help the gas in the tank move towards the fuel pump.

Did you check the plugs? How are they?

 

Hey there,
Just did a bumper to bumper check on the car by a reliable auto shop with emphasis on spark plugs and fuel pressure. Everything came out normal. The spark plugs are fine and fuel pressure was normal too. Now I just realized probably this is something that I have to live with and probably it's normal for my car. And I think I will just have to wait until the problem is super obvious if there is any.

I really appreciate your help and support on this.

 

Dear Sasnuke,
I have finally found the culprit. It was the faulty fuel pressure regulator!

As the fuel pressure regulator was replaced, the Toyota dealership overlooked it. Then one technician finally checked everything related to the fuel delivery system and this time he checked the pressure regulator once again and it turned out that the newly replaced part was malfunctioning. The injector and the fuel pump was perfectly fine.

So, the fuel pressure regulator was changed once again and it's been 3 months me testing the car and the hard start finally disappeared.

Mystery finally resolved! Thank you and everyone for all the help and support!

 

Thanks for following up with the solution.
I recall earlier in the thread fuel pressure was checked on multiple occasions and nothing abnormal was found...makes you wonder who and how they were checking the pressure...or maybe bad luck that the issue didn't present itself when the pressure was being checked.
Good on the tech that persevered and found the issue...to think a new part is faulty is definitely a last thing to check.