Hi i have a z24 2000 cavalier and its makiing odd noises..... Sometime the engine will make a knocking noise and then it wont..... if i rev the engine past 3000 rpm's it starts to knock really hard..... i think its a lifter but im not to sure bc it doesnt do it all the time just at higher rpms. The oil in the car is full ... what could it be if it just knocks at higher rpms and not at idle
thx josh

 

Josh, odd timing I JUST posted the exact same thing on my 1998 z24. I am curious what we find out. I assumed it was the timing. If it is a lifter that would make sense also. Watch your oil light on your cluster. If it randomly lights up I bet it is a lifter.

 

This could also be the lower end. Get out your screw driver place the tip on the engine and your ear on the handle and see if the knock is coming from the top of the motor or toward the bottom. If the top probably a lifter if the bottom probably a connecting rod or main bearing bearing is about to go. They don't always knock at low rpm's until they are really bad. The sounds should also be different. A lifter will be more like a taping sound where as a connecting rod will be more like a hammering sound. My son had this problem with his Sunfire and it was the lower end.