When I start my car to let it warm up, it starts up great and revs up to about 1800-2000 RPMS when the engine is cold.
Once the engine warms up a bit and the therm needle gets just over the C (cold) indicator, the RPMs start to come down from 1800 to 1500. Then it starts to bounce the RPMs from 1500 to 500 to 1500 to 500. It is like I am pumping the gas.
Once the engine gets warm to running temp, it does not do it anymore for the rest of the drive, unless the engine has a chance to cool down again.
Any help on how to fix this will be awesome. Thanks so much.
~Toph

 

Mine does the same thing. lol Iv tried to fix it but no luck.

 

Commonly air in the idle control valve on the back of the throttle body. You have water piping from the head across to the bottom of the throttle body, up to the idle control valve, and back to the engine. Could be a simple air bubble which some bleeding of coolant can fix, or it could be a blockage in the pipe under the throttle body or into the idle control valve. I've had both - but the first is much more likely.