Chrysler Neon 2000

Look, vehicle RPMs are factory-set. Adjusting them to accelerate the car isn't a solution, as the problem is still there even if you don't feel it. Now, as my colleagues have mentioned, the IAC valve regulates the idle speed using signals from other sensors. That's why you should check its operation, clean it, and finally, calibrate it. Check this first. Also, make sure all the filters are in good condition, and lastly, if possible, check the fuel pump pressure. Do this and let us know. These are the steps to follow; don't skip any just because someone told you they had the same problem and it went away after replacing the TPS. Do it step by step.

As Kikemec says, do it with a system, following the indicated steps. Another possibility that causes the minimum march to be unstable is a broken hose or any other erroneous air input.