Rough Cold Start Issue
 

Dear Members,
I have 2010 RX8 (AT) with 30K mileage and I need your help with a small issue.
I already installed new OEM plugs, coils, cables, air filter in 2017 and regularly change the engine oil at 3K miles (with 5W-30).
No aftermarket mods/parts installed. Only the catalytic converter has been removed (mileage is below than average).
The car has been working normally with stable idle and acceleration.
But due to a scratch on front bumper, I left my car for a paint job and they made a common mistake – turned off the cold engine and flooded..
After removing cables and cleaning the spark plug ports they eventually managed to turn it on.
But starting from the next day I have been facing following problem:
When I start the car in mornings, the engine starts normally hitting 2500 rpm and slowly starts to decrease.
But when it goes below 1500 rpm it tries to stall roughly with loud & unstable noise pushing tachometer up and down by 200-300 rpm.
It only happens for around 20 seconds during cold starts and after that moment rpm jumps to 2000 and then decreases normally towards 1000.
After getting warm it begins to work normally with silent, stable idles at “D” “R” “N” (playing slightly around 850).
While at “P” the idle is not stable (Jumps between 800/900).
I already checked the plugs, coils, cables. They are in normal condition. Also cleaned MAF sensor.
What do you think? What could be the problem?
Thanks in advance

Did you check engine compression?

Did you check engine compression?

Engine compression was checked.
The problem was clogged injectors.
Thanks for your support.