Uneven Idle

A few questions for your consideration below:

Which parts of the car were damaged by the accident?
Any wiring harness damage?
Any warning lights on?
What is the odometer reading now?
When you say the car "runs OK", how many miles have you driven since the car was repaired?
What mpg have you been able to achieve?
What tool did you use to determine that no DTC was logged?

In general, the hybrid vehicle ECU is responsible for managing power requests from the gasoline engine and the electric motors. However if you don't have any DTC logged then it will be hard to pin down the nature of the problem.

It is definitely not normal for the engine speed to "hunt". Idle speed should be closer to 1,000 rpm. Can you get the car into Inspection Mode? This will force the engine to run continuously.

To get there, make the car IG-ON and leave the gear selector in P.
Fully depress the accelerator pedal twice.
Shift to N. Fully depress the accelerator pedal twice.
Shift to P. Fully depress the accelerator pedal twice. Note that the hybrid vehicle warning icon will appear on the MFD.
Then depress the brake pedal and press the POWER button to make the Prius READY.

In Inspection Mode, engine rpm should be around 1,000 when at idle. Then if you depress the accelerator pedal less than 60%, rpm should increase to 1,500. If you floor the accelerator pedal, engine speed will rise up to around 2,500 rpm.

 

From what I've played with I don't think the car learns new
limits for the throttle position sensor, so you have to actually
set it to where you get a reasonable idle level. When I had mine
off briefly and didn't line it up *exactly* with the paintmarks
on reinstalling, the RPM would definitely shoot up a bit in
Neutral especially when the engine was cold. Still does it a
little bit, but I got tired of screwing around with trying to
eek one or two thou in either direction by tightening clumsy
screw-heads.
.
However, that wasn't really a "hunting" situation, so you might
have something different going on. Check the MAF? Any damage
to the O2/AF sensors? Is the throttle body working freely with
no mechanical hangups?
.
_H*

 

Both Patrick and Hobbit covered almost everything I would have mentioned. Regarding codes, is the Triangle of Doom on? A generic OBD II scanner won't be able to access unique codes. Regarding the MAF, any debris at all in the sensor can cause odd behaviour. I'm now convinced that routine PCV operation in a cold climate causes the deposits on the MAF, as my FJ and Prius appear to share the same MAF, and both had similar deposits If anything, my FJ had deposits a lot quicker on the MAF. Very easy to get to the MAF on an FJ, and once I cleaned it with an approved MAF cleaner, there was an immediate and noticeable difference in how my FJ ran, how it idled, throttle response, and how the auto shifted

 

I assume then, that the car was in a front-end collision. Why did you replace the throttle body - was that damaged in the accident? What DTC were logged when the original throttle body was still installed?

Given the relatively high "idle" rpm, I am wondering whether you might have a vacuum leak:

- Did you use a new gasket when replacing the throttle body?
- Is the oil dipstick fully inserted and the O-ring in good condition?
- Is the engine oil cap fully tightened and the O-ring in good condition?
- Are the two PCV hoses securely attached on both ends?
- Any damage to those hoses or to the intake manifold?

If you have a vacuum leak then the fuel/air mixture will probably be lean, but you might not notice a problem if you haven't been able to drive the car much.

 

That could cause issues too, but not set a DTC

If during installation even a speck of dirt from the housing were to fall onto the hot wires, that would be enough. The MAF is easy enough to get to on a Prius, it's a simple quick inspection