My daughter was driving on the highway and hit a puddle of water. Don't know what speed but now the car surges at idle, revving up and down.

I looked at the car last week and didn't see any water in the air filter or vacuum lines that were not attached.

I bled the air out of the coolant and that seemed to have fixed but the other day my daughter called me to say that there is a check engine light and the revving is back. I had her check that the gas cap is tight and there is coolant in the overflow bottle. That looked good.

She took the car to O'Reillys and had the check engine light scanned and she was given a printout of the likely causes. I didn't see the error code itself but the following list (in order of probability) is what was given:

Evap canister vent solenoid 5052
Evap canister 5893
Evap two-way valve 1023
Gas cap 897
Evap purge solenoid valve 448
Evap canister control valve 258
Evap bypass valve 176
Powertrain control module 147
Evap shutoff valve 115
Evap line 96
Vacuum hose 92
Fuel tank pressure sensor 66
Fuel tank 53
Evap leak detection unit 25
Evap canister hose 24
Fuel tank vent valve 20
Fuel filler neck 18
Evap purge solenoid wiring harness 4

Given the location of the evap canister parts (by the gas tank) I can see how the water might have infiltrated some of the parts.
However since the car is a 1999 model with 93k miles and no parts have been changed I'm going to go for the easy solution and replace the gas cap and radiator cap.

Anyone else have this similar problem and if so how did you fix it?