Petrol consumption is very high

My mini van has a s320v engine. Can you teach me how to fix engine timing? I have big problem petrol consumption is very high, like a one litter it can run 8.5 km only without air conditioning. When highway if I drive it can 11 km.
I did engine half overall but I could not get any trouble in engine. All things I clean and repaired. Also, spark plug and o2 sensor I changed. Also, I did clean throttle body petrol pump. I have suspected for engine timing. Do you have any idea about this issue?

I am sorry.
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