Knocking Noise After Letting Off Accelerator

bimspiration09 · 01-02-2017, 06:56 PM

Hi Everyone - I have searched high and low and can't seem to find a darn thing about the issue I'm having. I have an 09 335xi with a JB4 and DCIs. Bought her at 64k, she has 106k, and it was very well maintained before I bought it. Haven't had any issues, and routine preventative maintenance (plugs/coils/walnut blast/2 injectors) have been done since I bought it. Anyways...

During a hard pull, and right after letting off the accelerator, I'm getting this knocking noise that seems to be coming from right underneath the dash. It almost sounds like if you were to be knocking on wood...somewhat hollow sounding. It's only happening after abruptly letting off the accelerator.

Was having this issue for a little bit a few months ago. It disappeared, but today on the highway me and a 540 were having a little fun and I noticed it happened again.At first I thought it was my hoses that run across the engine cover - they were loose because a clip on the plastic hose cover broke and the tape I used to secure it ended up coming off. I ended up zip tying the hoses down, so they're secure.

Is this anything to worry about? Is something loose, or is it a bigger problem?

rockflageagle · 01-10-2017, 06:33 AM

I would guess guibo, CSB, diff or tranny mounts are worn and need replacing. Especially post 100k if they haven't been done already.

01-02-2017, 06:56 PM	#1
bimspiration09 New Member 2 Rep 18 Posts Drives: N54 335xi Join Date: Nov 2015 Location: Ohio iTrader: (0)	Knocking Noise After Letting Off Accelerator Hi Everyone - I have searched high and low and can't seem to find a darn thing about the issue I'm having. I have an 09 335xi with a JB4 and DCIs. Bought her at 64k, she has 106k, and it was very well maintained before I bought it. Haven't had any issues, and routine preventative maintenance (plugs/coils/walnut blast/2 injectors) have been done since I bought it. Anyways... During a hard pull, and right after letting off the accelerator, I'm getting this knocking noise that seems to be coming from right underneath the dash. It almost sounds like if you were to be knocking on wood...somewhat hollow sounding. It's only happening after abruptly letting off the accelerator. Was having this issue for a little bit a few months ago. It disappeared, but today on the highway me and a 540 were having a little fun and I noticed it happened again.At first I thought it was my hoses that run across the engine cover - they were loose because a clip on the plastic hose cover broke and the tape I used to secure it ended up coming off. I ended up zip tying the hoses down, so they're secure. Is this anything to worry about? Is something loose, or is it a bigger problem?
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01-10-2017, 06:33 AM	#2
rockflageagle Enlisted Member 1 Rep 43 Posts Drives: 2008 328xi Join Date: Oct 2016 Location: VA iTrader: (0)	I would guess guibo, CSB, diff or tranny mounts are worn and need replacing. Especially post 100k if they haven't been done already.
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