There's a strange problem with my TSX. I got the car three weeks ago and only having 600 miles on it. But whenever I start to drive the car, there is always a thunk noise when I hit the 20 mph mark. It usually happens when the car is sitting in my garage or anywhere for 2+ hours, and when I start to drive it'll have the noise again...

Anybody know what the problem might be?

 

It's not a problem. It's your ABS system test firing.

Old Hondas used to have the ABS system siezing because it was rarely used. So new ones have this test fire system both to ensure longevity as well as to serve as a test to check that the ABS system is working correctly.

 

Thanks a lot, I was scared when I first drove it.

 

I agree with Aaronng, the ABS performs a self test every time the car is started. Basically it does a quick pump of your brakes, and because the car is cold, that is the noise you hear. Many new cars equipped with ABS do this as well.

 

Thanks for explaining that one! I have been wondering what that noise is for 6 weeks now. I thought it might have been the AC, but I eliminated that.

 

Acura should state this in the manual. This information is good to know and would save a few people from going to the dealer to report an "issue."