Ford escort zx2 2002 coupe not fully accelerating, hesitates and then clicks and goes?

My ford escort zx2 2002 coupe has been driving fine for a while, only 55k miles on it and recently got some pipes and a vacuum tube fixed. But recently I ve been driving it and sometimes on take off my cars rpm will go up a bit and it feels like it is hesitating to go, and it stays like that for 1-2 seconds and then clicks! It clicks with the rpm and drives smoothly. It s happened before and my dad said it was from a dirty spark plug or filter, but that was 2 months ago. What would you think the problem is?

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