four times vs fourfold

four times is not an adjective while fourfold is an adjective.

Word	Noun	Adjective	Verb	Adverb
four times	No	No	No	Yes
fourfold	No	Yes	No	Yes

As adverbs, four times and fourfold are synonyms defined as:

four times (adjective)	fourfold (adjective)
	having four units or components
	four times as great or many

four times (adverb)	fourfold (adverb)
by a factor of four	by a factor of four