I have an 01 monte carlo SS, lately i've noticed that the car is hissing, and I haven't really investigated it alot but it seems like its coming from the back. It only happens when I accellerate aggressively, I don't have to do it but sometimes I have to get up to speed to merge, etc. etc. And I wanna know whats wrong with it. Again, it sounds like its coming from the back tire area but i could be wrong.

 

Could be a simple vacuum leak too. When my throttle body gasket went bad I would hear a hiss from it.

 

I'm not really good with cars, is this expensive to fix/neccassary to fix?

 

Not really. Just a small gasket. I messed up mine and its making a huge hissing sound. and sucking air through crank case.

 

my check engine light is now on....

 

I would think a gasket leak or ???exhaust leak???

 

Id say gasket leak

 

Is this something I have to get fixed and does autozone do free check engine light checks

 

Id get it fixed & yup they do

 

If it sounds like it's coming from the rear of the vehicle (and the CEL is now on) I'd check your gas cap. It could also be a restricted or defective vent solenoid but I'd check the gas cap first.

Yes, Autozone will read your codes free of charge.