If you have to keep ur foot on the gas in order to keep the car running, and turn the a/c on in order for it to iddle to the level to operate without holding ur foot on the gas

A lot depends on what vehicle you are working on. Most likely it is a fuel injection system using gasoline as the fuel. If this is it, I would first try cleaning out the throttle body and cleaning the idle control motor. You can do this by buying a good quality intake cleaner and spraying it into the throttle body while the vehicle is running. A good cleaner I found was SEA FOAM. Take a spray nozzle to spray it into the throttle body.

indicates that the idle circuit or system is not operating as designed .
could be a sensor fault
best have the fault codes read to find the area of the problem

What year make and model of vehicle? In some cases, when the battery is disconnected/removed, the vehicle will need an idle relearn procedure. This can usually be accomplished by keeping the vehicle running with your foot on the gas pedal and gently revving the engine til idle will stay by itself. It is then a good idea to drive the vehicle for any other module relearn that may be necessary. In some cases, the relearn procedure must be accomplished using a scan tool.

To fix the jerking rotate your tires and what do u mean by cuts when idling if it cuts off then there is a chance there is water in your gas tank due to precipitation just go to the gas station and put about a full tank but u need to keep a full tank in it when your not using for a while when I was locked up I couldn't let it idle without turning off so I would just sit in it and barley press the gas until it thought it was ok to let go and it ran good till my starter went out and the switching off you probably need to get a new gas pump line or whatever it's called I forget.

Check TPS -Throttle Position Sensor

May be worn out

Test it --not replace-- unless it has failed a test

Also the fuel pump maybe worn out as well

There r 2 cables on a gt 6 speed that r located at the top of the engine in back.. Do not touch the rear cable unless ur tibrron is shifted hard. The front cable is ur drift idle, theyre 2 nuts tightend den to secure it at a certian level , untighten the nuts and simply ajust the 2 nuts backwards do the cable isnt so tight and allows the engine to drop idle wen accelerater isnt pressed. Then do the same to the rear cable(2nd) cable untill u have ur tibron sounding just right..only sol_tion

Idle air control valve might be broken or pcv valve pipe broken

Have the idle bypass valve checked, also called idle air control valve.
If that valve is stuck in the closed position, it's not allowing the fuel to bypass the throttle plate to keep it idling, resulting in stalling, but will keep engine running if the pedal is pushed down.

check fluid level but warm the car up first and check while running if low add 1/2 a quart at a time until it is in the good zone on the stick put ur foot on the brake and put it into every gear starting with reverse then shut it off and turn it back on it should work fine

Does van stay running when you hold the gas pedal down? Check fuel pressure at fuel rail should be 30 psi when key is turned on. EGR valve and EVP sensor also control idle.