Noise when letting off accelerator

Hi All - just so I can start off my forum history with a truly noob question here it goes...

I bought up a 05 Passat with a manual swap in it. The past few days I've been putting around town teaching myself the ways of the manual shifting. Most obnoxious noises and performance bugs I can tie to user error and understand what's happening.

One thing I cannot is when I let off the accelerator too quickly the car tends to really dislike this. It becomes more prominent when in lower RPMs say in 2nd gear going through a rolling stop or something of the sort. It sounds like a whack or a bang. I feel like it could just be poor gear choice and I'm bogging the engine or something, maybe just not smooth enough.. it just seems aggressive. Thought I'd check here first before checking motor mounts etc thx!

Check timing marks. Verify timing and you should also check fueling and take some logs with vcds.
Sounds like the exact same issue I have with overfueling

I’d put my money on a bad/nonexistent snub mount (the motor mount at the front of the engine) I had the same symptoms as you and replacing that did the trick. It’s cheap and easy to get to.

Is it an engine bang? Or like a log hitting the car thump bang? If it's not engine noise, definatly a mount. When I installed my dark forest stage 2 mounts the bolt was wrong and left about a 1" play. But it only thumped when I get the motor going then rapidly let off. Is this more what's going on?
I'll sell you my motor mount set, I parted out the Jetta and have the stage 2 or 1.5 yellow mounts.

Mount bolts being loose cause bangs and thumps, check all mount bolts.

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Mongler98 said:

Is it an engine bang? Or like a log hitting the car thump bang? If it's not engine noise, definatly a mount. When I installed my dark forest stage 2 mounts the bolt was wrong and left about a 1" play. But it only thumped when I get the motor going then rapidly let off. Is this more what's going on?
I'll sell you my motor mount set, I parted out the Jetta and have the stage 2 or 1.5 yellow mounts.

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Mongler98, .....never mind

ixanay, this has nothing to do or in common with your car other than both cars are a diesel.

Check out your motor and trans rear mounts but also control arm bushings for tears. Not that uncommon on those cars.

Thanks for all the replies, I'll take a looksie when I can get it jacked up. So used to crawling under lifted trucks this will be quite the change. I took it out for a spin today and the easiest way to reproduce was in 2nd around 2300 rpms let off the gas and back on. I could rock it back and forth. I think it's a combo user error and worn mounts but will update the thread when resolved thx

ixanay said:

Thanks for all the replies, I'll take a looksie when I can get it jacked up. So used to crawling under lifted trucks this will be quite the change. I took it out for a spin today and the easiest way to reproduce was in 2nd around 2300 rpms let off the gas and back on. I could rock it back and forth. I think it's a combo user error and worn mounts but will update the thread when resolved thx

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if theres too much slop in the DMF this will cause the "play" you experience with the gas on/off

bmwM5power said:

if theres too much slop in the DMF this will cause the "play" you experience with the gas on/off

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Interesting thought. The manual swap has less than 5k miles on it and the swap was done by a trusted mechanic. Do you know if a new DMF is typically installed during these swaps or if they just bring it along with the donor transmission? Will hopefully be getting extensive records on this vehicle soon

ixanay said:

Interesting thought. The manual swap has less than 5k miles on it and the swap was done by a trusted mechanic. Do you know if a new DMF is typically installed during these swaps or if they just bring it along with the donor transmission? Will hopefully be getting extensive records on this vehicle soon

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It depends on what's requested. Mine was a swap and it had DMF I put in SMF.

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