Not likely. Code P0138 is------O2 Sensor Circuit High Voltage (Bank 1 Sensor 2).
No, it is not a bad or loose gas cap. It is a problem with the secondary air pump.
A bad fuel cap can make your check engine light go on. It shouldn't cause your car to run rough or die.
Most probable cause: Replace Gas Cap Most probable cause: Replace Gas Cap
Probably a bad gas cap.
The most probable cause is a vacuum leak or a bad fuel cap. Inspect all the vacuum hoses for damage and buy a new fuel cap, making sure it is tightly on the vehicle.
Bad coil? Bad distributor cap? Bad distributor rotor?
Not likely.
Bad thermostat, cap and radiator is a common cause.
It could either be a bad ignition coil, a bad ignition rotor, a bad ignition cap, a bad ignition control module (if equipped), or a bad coil to cap wire.
A common cause for that code would be a loose gas fill cap or a damaged/missing O ring seal on the cap.
Both of these codes indicate a leak in the evaporative emissions control system. The most common cause of this code is a bad fuel gas cap.
It means Evaporative Emission System Leak. Start with the gas cap. A loose gas cap can cause this.