my car was missing so i decided to clean my maf. i took it out and cleaned it. then put it back in. after i let it dry. i also changed my spark plugs. after everything was put back together i fired it up. and the engine started knocking bad. does anyone know what this means? thanks

 

If you mean knocking like "knocking and pinging", check your timing. What octane are you using? Turbo or n/a engine? Also check ecu codes.

If you mean knocking like "metal on metal", then it could be a cam / valve train problem, or a rod knock.

Video clip?

 

You dropped something into the cylinders when you changed your spark plugs. Now you'll have to remove the heads.