I routinely hear the word "efficate" being used. For example, "The most powerful way to efficate a change in the system is to participate."
I do not find entries for this word in common English dictionaries, but I do not have an unabridged dictionary.
I have checked the OED (I'm not sure if it is considered unabridged), and it has no entry for "efficate". It does have an entry for "efficiate", which is used in the same way.
Wordnik has an entry for "efficate" with over 1800 hits, thus providing some evidence for the frequency of use.
I personally like the word and find the meaning very clear and obvious when others use it.
If it's not currently an "officially documented" word, perhaps its continued use will result in it being better documented.