Engine backfire

When it shuts off is it like you turned off the key? Or does it act like it is running out of gas? When was the last time it had a tune up?

The description sounds like a crankshaft position sensor that is failing. They are known to become heat sensitive. It is in the front of the engine down on the bottom in a bracket near the crankshaft. It is a simple remove and replace sensor.

The camshaft sensor controls the timing but they generally do not fail this way, but just in case, The sensor is on the back of the cylinder head, held in with one bolt. It is a plug and play item. You remove the bolt, remove the sensor by wiggling it to free it and pull it out. Apply some oil to the new sensors o-ring, slide it into the hole and tighten the bolt and plug the connector in.

Before you replace either one there is a simple way to test them. Go to the local office supply or store that carries "canned air or computer duster" Put on some gloves to protect your hands. Now start and run the Tracker until it shuts down. Turn the can of "air" upside down and spray one of the sensors for about three to four seconds. Protect your hands and eyes as "canned air" is a close cousin to the refrigerant used in the AC system and can freeze your skin if you let it. Try to start the engine. If it starts right up that sensor was the problem. If not spray the other one and try again.
Do not spray both before you try to start the engine or you won't know which one was faulty.

Below are pictures of both the one with the long wire is the crank sensor.