how do I find out if my 1994 Toyota Celica is a 1.8l or a 2.2l?

Toyota usually puts it right on the engine "1800=1.8" "2200=2.2" if it is not placed on the engine itself you will want to look for a white tag under the hood. Possibly on the intake in some applications, that will tell you as well. If all that fails call a parts store and give them your vin #, they can tell you

Call a local dealer and give them the VIN# number.