# Knocking



## Loms1977 (Nov 20, 2008)

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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## 700Rocket (Mar 29, 2008)

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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## WanaGTO (Sep 7, 2008)

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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## alsgto04 (Nov 21, 2007)

Good thing i read this thread mine does the same thing i never could figure out what it was.


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## GTO-SRI (Sep 21, 2008)

hahaha i always wondered what that was


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## Aramz06 (Mar 2, 2008)

Loms1977 said:


> 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?  :cool


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## GTOsarge (Oct 9, 2007)

Mine does the same thing.


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## monstermike281 (Feb 17, 2010)

and all this time i thought i was freakin loosing my mind and i told my old lady she was crazy. Dont i feel like an a$$


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## preach (Jan 24, 2010)

I just heard this noise a couple of days ago and was like wtf?


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## RJ_05GTO (Jul 6, 2008)

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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## FastFrank (Jun 12, 2009)

I've never heard this before, but I'm glad I read this thread in case I do ever hear it.


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