I'm new to the forum, I'm hoping some one can help me.
So I start my car to go home and notice a clacking sound, i'm driving home it gets louder and the car starts stumbling when it would idle i take it to autozone and they give me these trouble codes p301 and p4040.
I checked the egr and the pindle was stuck, cleaned with carb cleaner and now springs freely. checked the spark plugs, wires & coils and they look visually good, car is still stumbling.
i found a rocker arm to be very loose and holding by a few threads, i guess the intake valve to cyl 1 wasn't opening because it wasn't being compressed, torqued back to spec & checked the rest of the rockers.
i start the car back up and the noise is gone but my monte is still misfiring, now i have P0300 multiple misfire. Any leads on what it could be? I appreciaty all the help.

I'm going to buy a compression tester and check the cylinders for compression tonight. wish me luck.

 

it's a 2000 monte carlo ls with 160xxx