Recently got my car scanned. Everything was normal except Short and long term fuel trim. I heard that fuel trim should be Zero in ideal case. Mine are 1.33 %. What does that mean? is it too rich?

 

On time is the length of the injector pulse, more on time more fuel added, less on time less fuel added. This is what the LTFT and STFT are, LT is what the car normally does, ST is for current/immediate adjustments. +% more fuel -% less fuel.

You will most likely never see a constant 0% fuel trim. That would mean everything is perfect, engine, fuel ratio, load, etc. This is highly unlikely as there are too many variables in the engines components, air density, load conditions, and driver demand.

If the STFT stays under 5% fluctuation I would not worry about it.
If LTFT are getting closer to 10% then there might be something slightly out of tune, or simply a worn engine.
Higher LTFT percentages or a maxed reading there is probably something wrong with the O2S or a vacuum leak/fuel pressure issue.

At 1.3% I would say you are doing pretty good.