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Discussion Starter · #1 ·
Hi Guys,
Can somebody give me a toughtful advice what is the common reasons for rough engine noise on 2.4 theta engines(2007 sonata GLS)? It has smooth idle, does not burn oil at all, but kind of rough (I would say ratling) noise after 1700-1800rpm and poor, sluggish acceleration. What is the most common reason for engine failure on this model(oil pump, timing chain/tensioner or....)? What would you recomend to look at 1st? Thank you!
 

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Are you sure it's the engine making the noise? It might be an engine noise but it is more likely a catalytic converter or a transmission noise. The rattle could be a converter rattle which would lead to clogging the exhaust and reducing power. Maybe. Check by banging on the converter case under the car when the car is cold. If the converter rattles when you hit it I would suspect it needs replaced. Could also be the pump in the transmission. When these fail the impeller will slide back & forth on the shaft banging into the case. It can also sound like a rattle. Might also impact power by reducing fluid pressure. Maybe. You'll need to take this to a trans shop to diagnose. The simplest test is to unbolt the torque converter from the fly wheel and start the engine. Rev the engine and see if the noise disappears.
 

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Discussion Starter · #4 ·
Are you sure it's the engine making the noise? It might be an engine noise but it is more likely a catalytic converter or a transmission noise. The rattle could be a converter rattle which would lead to clogging the exhaust and reducing power. Maybe. Check by banging on the converter case under the car when the car is cold. If the converter rattles when you hit it I would suspect it needs replaced. Could also be the pump in the transmission. When these fail the impeller will slide back & forth on the shaft banging into the case. It can also sound like a rattle. Might also impact power by reducing fluid pressure. Maybe. You'll need to take this to a trans shop to diagnose. The simplest test is to unbolt the torque converter from the fly wheel and start the engine. Rev the engine and see if the noise disappears.
Thanks a lot Disaster. Makes sense. I have no check engine or anything lighting on the dashboard, but I feel it's not running as it used to. I just want to prevent it from premature death. It’s ~140K already and still runs 42 miles every day. Does not burn any oil and I hope there is still a resource to run another 40-50K if I invest a little in preventive maintenance. I’ve heard many people complain about timing chain stretching and tensioner giving up. Is that common issue for the 2.4 engines or it applies to the 3.3 mainly? Thanks! I’ll check the converter this weekend.
 

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Two other things to consider: low octane fuel (causes pinging) and faulty/incorrect oil filter.

The oil filter doesn't come to mind for most people but if the bypass valve doesn't meet Hyundai specs then it cycles open/closed making a rattling sound.

Regards,
GEWB
 

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Does it make the same rough sound when it is not in gear? If so, let someone else keep it at 2K rpm when it is in Park and try to verify in the noise comes from the engine, maybe, indeed, like some other people said the sound comes from exhaust system.
 

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Discussion Starter · #7 ·
ThanX! Appreciate your input. Actually by low octane fuel you meant that should try driving it with 93?
 

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Discussion Starter · #8 ·
Does it make the same rough sound when it is not in gear? If so, let someone else keep it at 2K rpm when it is in Park and try to verify in the noise comes from the engine, maybe, indeed, like some other people said the sound comes from exhaust system.
Yes, I have tried that and it looks like it comes from the engine. I would say it's louder under the car than if I just open the hood and listen the engine from the top. Thanks!
 

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Yes, I have tried that and it looks like it comes from the engine. I would say it's louder under the car than if I just open the hood and listen the engine from the top. Thanks!
Like someone said, have your oil changed and be sure to use a Hyundai filter and see if that makes a difference. Shouldn't cost that much.
 
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