Hyundai Veloster single knock when accelerating or taking foot off gas?!

General Discussion
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1

I’m looking at a car for sale and the weirdest thing happened…

So this is a 2013 Manual transmission hyunda veloster (non turbo) with 80k miles on it

Car was clean, engine was clean. Idled perfectly and sounded perfect when I revved the engine up from neutral. No sounds at all.

Car drove and shifted very smooth as well, HOWEVER.

I turned the radio and the AC all the way off and I would hear this weird knock noise (literally like a single knock on hard wood) when I would accelerate OR if I took the foot off the gas? it sounded like it came from under the hood but I can’t tell where it was coming from? Sometimes it sounded like the right side? Sometimes the left? It’s not a constant knock and it generally happened if I gave it gas or let off the gas?

I have no idea what the hell this could be? Anyone have an idea?

It happened a lot but it wasn’t constant? I don’t THINK it’s the engine but I’m not a mechanic by any means.

2

it could be a broken motor mount.

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3

But wouldn’t that make it clunk around when revving it up period? Even from neutral? I don’t think that’s it. It revved up flawlessly when in neutral.

It also didn’t clunk when actually accelerating? It’s just like it happened when you first give it gas or if you take your foot off.

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1rst thing I’d suspect is motor mount as @weekend-warrior stated, but could also be suspension (bad tie rod, ball joint, control arm) especially if you feel it in the steering wheel.

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I felt nothing in the steering wheel.

But I don’t understand how it could be a motor mount? Wouldn’t that make the motor shake around when accelerating at all? It’s not a constant shake? It’s single knocks

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And again, I can rev up really high in neutral and NOTHING happens. Sounds perfect

7

they tranny is not engaged not putting torque on the engine.

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8

It’s not a transmission clunk. I don’t FEEL anything slipping. I don’t feel anything at all, it’s just a sound. it shifts perfect. It makes zero sense to me lol

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Bumps, Thuds, and Vibrations: How to Diagnose Bad Car Engine Mounts! - YouTube

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I know what bad engine mounts feel like, I’ve experienced that. The engine does not move or shake at all.

Again it’s just a weird knock single knock sound (no car movement) when I put my foot on the gas or let off the gas.

11

Based on the discussion thread… it could be a mis-adjusted exhaust pipe striking the corner of the engine cradle or underside of the car. This could happen if the previous owner bottomed the car on something and knocked the pipe up towards the car body. Take a look under the car on a lift. Any exhaust that is within 12mm (1/2 inch) or so up towards the engine is suspect. There might be a shiny spot on the pipe itself.

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Could it be like a driveshaft issue? Like some kind of slack somewhere? Idk… I don’t FEEL anything at all. It’s just a noise.

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It could be… but it is easy to check simply by checking the play in the shafts.

It COULD be a lot of things. Kicking around ideas on the internet isn’t going to find it. Noises must be heard and felt to be tracked down. The noise is clearly in the driveline somewhere. Get the car in the air, get the wheels off and look for loose items is the only way to proceed.

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Well I can’t, it’s a car at a dealer I was going to purchase. I was wondering if it was an expensive fix or not.

15

This is easy , ask the dealer to fix it and if they won’t just move on and find something else . It might be a cheap fix or expensive but why take a chance.

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16

it’s a used car lot that buys from auctions. They won’t

17

And now you know why it was at an Auction . Pass on this.

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18

Time to pass on this one most auction cars need a lot of work and the dealers send them there because they are to expensive to fix.

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19

I have only purchase one car from a non-dealership lot. They allowed me to take the car for the weekend and have my mechanic inspect it. If this used car lot will not allow inspection, run, don’t walk, run away from them.

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20

Concur w/advice above, if you’re not allowed to have your own shop do a pre-purchase inspection before deciding, suggest to let this one go.

As far as what could be causing it, all the ideas above are definite possibilities. If you notice it when you rev engine in the driveway, that would most likely be engine/transmission mounts. If only when driving, my first guess would be abnormal play in driveshaft/cv joints, depending on how its configured. If it uses rubber-like CV boots, its fairly easy to see if the boots are torn just by peaking under the parked car.

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