My car makes a noise while accelerating

My car has been having trouble accelerating and it makes a noise while accelerating. I took it to autozone and the machine read P0011 but my check engine light hasn't come on. My mechanic said without the engine light on he can't get a diagnostic reading. I got tune up thought that was the problem but the problem still persists.
Acceleration causes hesitation. Upon giving it gas it makes this loud noise like a rattling. Took it to my mechanic today and he didn't hear it at all.But i heard it all morning long.