Yesterday my check engine light came on and I rec'd the warning that my gas cap was loose. I checked the gas cap and everything appeared fine. This morning I went to Auto Zone and had the check engine light diagnosed and the employee told me my gas cap may be loose because it shows air is getting in to the fuel system. I was planning on leaving on a 500 mile trip Tuesday does this present a problem? The car seems to drive perfectly and I do not notice any problems at all even when punching it.

 

Sounds like a large leak in the evap system, car should run fine, but this is usually a pita to track down.
I bought my car in Fl and drove it to CT like this

 

Is has to do with the vapor recovery part of the emissions system. Periodically the control system will open a valve from the charcoal canister to manifold vacuum to burn up the trapped vapor.

Normally there would be a slight vacuum pulled on the gas tank when this happens and if the vacuum can't be achieved due to a leak, say because the gas cap is loose, then you get the error.

If the gas cap seals is good then the cause might be a crack in the canister or the canister close valve (CCV) might be stuck open.

You won't pass an emissions test eith that error code logged, but there is no significant risk to the car

 

What were the exact OBDII codes? You cannot depend on what the code reader says it means.

Gus
www.jagrepair.com

 

If you have a local shop with a smoke machine, this will greatly improve your odds on finding that leak more quickly. It doesnt have to be a "Jag" shop! The idea is to attach the smoke machine to the system, either by way of the fuel cap opening or the throttle body, pressurize the system slightly with pressurized smoke, and go looking for any signs of leakage in the plumbing or intake. (the smoke is easy to see at leak areas) But, it would really help to have the codes first to get you started properly! There is a canister vent valve and an attached hose which normally vents at the rear chassis area when the vehicle is parked. Dont let that fool you. You will have to find, and block off the vent hose from the canister to accurately indentify the real leak.

 

Get the codes first to verify the real problem.

Gus
www.jagrepair.com