My 08 TL is at 75,000 miles and I've been intermittently getting the 'tighten fuel cap' message. I replaced the cap before learning that there is a common issue with the Purge Control Valve, and of course the new cap didn't solve the problem.

I've been getting this message again recently but there is some drivability issue as well. Pulling from a stop there's a slight lag when pushing the pedal and during driving as well. This throttle response issue comes only when I get the gas cap message.

Does the purge control valve typically cause any other issues other than the dash message? I'm wondering if it might be some other issue in this case.

 

Make sure the cable to the APP sensor is adjusted correctly or the sensor could be faulty. I just replaced mine due to failure and the car is very responsive now.

 

Check for Broken hose. The same hose that feed the the purge sensor