I bought a replacement gas cap for my Camaro, but I realized that it's vented, whereas my stock cap is not. Does it matter? Why?

 

Im no expert but i think that the fuel system is supposted to be preasureized. Because right after i fill up sometimes my car seens to be a little slugish. IDK.

 

It's supposed to be a closed system. I doubt the EVAP system will function correctly with a vented cap.

 

It will most likely throw a code or "Service Engine Soon" or whatever light you have in a 98. A loose gas cap will do that too. Altho with all you mods who knows?? The system should be under preassure.

 

Should I assume that the replacement gascap I bought 2 years ago is vented?
My old cap would make a PSSSSSHHHHHHHHHHHH! sound when unscrewed. This one does not.

No codes have been set.

Is there a way to tell by looking?

 

I don't think the 93-97 cars will throw a code if they don't have a gas cap. I thought it was just 98+ cars. I could be wrong though.

 

FI systems are under pressure and require a non-vented gas cap. Thats why you hear that swish noise when you unscrew the cap. So buy a new cap, about $7 at the Dealer.