Odd idle surges of this sort can be caused by small variations of the output of your throttle position sensor, or TPS.
Hi, my name is Ed. Welcome to Just Answer!

TPS is used as a major input to the engine's fuel management system and should be a direct indication of the actual throttle valve opening. Its job is to watch for the throttle to be opened and then adjust the idle air control (IAC) valve and spark timing accordingly. A small increase in perceived throttle opening will inspire the fuel system to anticipate an acceleration event and it reacts by increasing spark lead and opening the IAC valve a bit.

If the TPS signal is in error, these actions are carried out without merit and the engine speed will increase for no apparent reason. Unless the error is big enough, you won't necessarily have a trouble code set, but the TPS can still be at fault.

To check this easily, first identify the TPS which is mounted on the driver's side of the throttle body and will be in direct line with the throttle shaft. It's a black-colored sensor held in place by two #25 Torx bit fasteners and will use three wires in its connector. There will be only one of these in this location.

Tap on the TPS lightly with a small tool with the engine idling. If this immediately causes the engine to flare, you've identified an erratic TPS as the cause for your idle flares.

Measuring TPS output at the center of the three wires is a better way, but it means you'll have to break the digital multimeter out. Set it to the 20v DC scale, ground the black test lead and backprobe the center wire of the three circuits at the TPS. Normal idle (closed throttle) output will be between 0.5 and 0.6 volts on this model, but actual output varies a bit.

What's important is that the voltage remains steady at closed throttle when the sensor is tapped... an increase of only 0.06v above its lowest key-on voltage will tell the engine controller to enter its idle-up program which is probably what you're experiencing. It's the INCREASE in voltage that causes this, as the engine controller looks for a throttle opening, whether real or imagined.

Replacement of the TPS is easy, requiring only the removal of those two screws. Be sure to rotate the sensor counter-clockwise (against the TPS internal spring pressure) before fitting it to the throttle shaft. There will be spring pressure against the TPS as it's rotated into position if it's been properly mated to the throttle shaft.

Let me know if you have any questions or problems. I'll be glad to help.

Good luck,
Ed