I have a 92 honda accord lx and the problem with it that it take too much gas about only 16 miles per gallon.

If you haven't done so already, change the spark plugs and the fuel filter, and put a bottle of fuel injector cleaner in the gas tank. This should help.

Start with a tune up. Always take care of the maintenance to narrow the problem. It sounds like fuel isn't getting combusted correctly. Weak spark or fuel delivery is possible.
Change the air filter, and the spark plugs. Check the resistance in you plug wires with an OHM meter to the specs in the manual. Check for any small cracks in your distributor cap, and replace if suspect.
Run some injector cleaner to your fuel tank, and check the seal area of your injectors for any leak sounds. They do have fuel injector kits to replace the o-rings when they go out. The injectors are usualy easy to access. A mechanic stethescope can aid in listening with some isolation.
Check the fuel filter for any leaks at the connections.
Fuel pressure regulator could be suspect if the car isn't running well. It is easy to replace this part.
Smell any gas under the hood? Look for leaks with engine off, but key to ON, so the pressure is there.
At worst, it could be worn valves or the valves not seating correctly. This would require the heads to be pulled, so the valves could be removed and the seats in the head can be repaired at a head shop.
Good Luck!