its something like that. I'm failing the system readiness test. Any idea what this is? I could only think of like the fuel charcoal filtering canister/system.

 

Yes the EVAP system consists of the canister, a purge valve, and a vent valve. The purge valve is on top of the engine; make sure the cable and the tube are properly attached. The canister and the vent valve are sandwiched between the fuel tank and the floor pan, so you have to drop the tank to get to them. If you have one of the older 4th gen fbodies it may be inside the left-rear quarter pannel; take out one screw and part of the inner fenderwell linner comes out.

 

Is it the small cylinder deal that has the hose running to the front of the intake on the drivers side? It can be seen in this pic?



It's a 98 so if its the canister or vent valve, hopefully it's in the quarter panel.

 

Loose gas cap?

 

Take a look at this thread:
https://ls1tech.com/threads/showflat...31&fpart=1