Hey all!

I have a 2012 manual transmission, and I drove it on a two hour highway trip. I usually go about 75, so I stayed in 6th gear for most of the trip. I did drive into some torrential rain, and it was so bad we all slowed down probably below 45. I noticed however when I exited the highway, as I downshifted and put it in neutral to stop at a light, the RPMs were bouncing from about 1000 to 2000, as if I were hitting the gas pedal to rev the engine. I double checked where my right foot was just in case it was actually me, but it was definitely the vehicle. When I got to my destination and pulled into a parking spot it did the same, I reversed it to straighten out, put it back in neutral and there was no revving.

Any ideas of what could have caused this?

 

Maybe the rain got some humidity / moisture on the MAF Sensor..the sensor that is on your air intake. The ECU could have flipped out, but it would have thrown an engine light.

Also do you have a Cold Air Intake?

I have been driving Manual tC's since 2005 and never experienced your issue.

 

Theres no cold air intake (but I am thinking of installing one).
My first thought was if the water had messed up any sensors, but I wouldn't know what to check.

 

The only time I've seen a manual rev in neutral is when the throttle body gets disconnected coz it doesn't know what to do (this is usually from forgetting to plug it back in after maintenance/upgrades). I'm partial to thinking it's either dirty or the MAF got dirty/wet as well. A dirty MAF will make the car do all kinds of weird things.

 

I am on the MAF bandwagon. I have almost hydro-locked before because I had a Cold Air Intake during a bad storm. I was able to take a hair dryer to dry the Filter and MAF and things were fine after about a day. OP, You should clean your MAF sensor, but do it right or you will kill a $200 sensor.

Give your Throttle Body a quick overview to make sure a wire did not get chewed up or get disconnected.

Also I love my Cold Air Intake. During the summer there is a 60+ degree difference between Engine Bay air and Outside Air.