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I am hoping someone might know what this could potentially be. I typically start my car, let it warm up, and then head to work. About 2-3 minutes into my commute I usually get stuck at a stop light. This is when I hear what sounds like someone knocking on a wooden door. It only happens right after start-up when I am stopped at the light. On the days when I make the light I do not hear it. It is 4 consecutive knocks, like I said, like a knock on a door. The sound seems like it is coming from the passenger side rear of the car. The first time I heard it my wife and I were coming home from dinner and we both turned because it sounded like someone knocked on the car to say hello. I haven't a clue.

I have no warning lights, no squeaks, no rattles, etc. I am at a loss. It does not happen everytime so there is no consistency so I do not feel like it could be replicated by a tech at the dealer.
 

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Yeah its a normal noise. Much like everything else on cars its usually louder when the parts are cold. Something to do with the Evap system running a test, it makes a knock knock knock sound in the rear. If its annoying loud then that may be a problem but all the cars do it. Its just doing a little self check. I know the part is right above the rear diff and its a black box mounted on the floor of the trunk.
 

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HAHAHAHA...this thread made me laugh because the same thing happened to me. I got stopped at a light coming home from work and I hear it. I instantly got pissed off and turned around because I thought someone was hitting the car! Then I just thought it was a ghost in my backseat. Good to know its no big deal....it does sound just like a knock on the the car HAHA
 

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I am hoping someone might know what this could potentially be. I typically start my car, let it warm up, and then head to work. About 2-3 minutes into my commute I usually get stuck at a stop light. This is when I hear what sounds like someone knocking on a wooden door. It only happens right after start-up when I am stopped at the light. On the days when I make the light I do not hear it. It is 4 consecutive knocks, like I said, like a knock on a door. The sound seems like it is coming from the passenger side rear of the car. The first time I heard it my wife and I were coming home from dinner and we both turned because it sounded like someone knocked on the car to say hello. I haven't a clue.

I have no warning lights, no squeaks, no rattles, etc. I am at a loss. It does not happen everytime so there is no consistency so I do not feel like it could be replicated by a tech at the dealer.

Do you have a PHAT exhaust? :D :cool
 

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Mine does the same thing.
 

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Yep LOL!!!! Ive heard that noise several times before. The first time i was sitting in my carport with the engine running and i thought somebody was tapping on my rear passenger side window. But after i heard it a few times i figured it was something with the car. I have never heard any other car make that type of noise before.
 
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