Genesis sedan 2015 3.8 V6 AWD RPM drops and shakes when wait for traffic light!

[dakwonhee]

Hi!

My Genesis sedan 3.8 V6 AWD suddenly RPM drops under 500 and shakes when braking for traffic light.
Please see below youtube link.

https://youtu.be/74XwSRv02uE

I sent the link to my dealer and wait for the response.

Please share your thought what is causing it and how to fix it!
I also update the dealer response.

Thank you and Happy New year to everyone here in this forum!

Best Regards, Dan K

 

[jsmit86]

Is this new recent behavior? Shaking is not normal for 3.8 AWD in the US.
Some drop off in RPM is normal when coming to a stop, especially if the A/C compressor kicks in, but not shaking.

 

[dakwonhee]

Thanks for the info.

It started recently... I have no idea what triggered this behavior.

two weeks ago, the dealer cleared the CPU's faulty codes that triggered "Limp mode".
no causes found for the "Limp mode".

but the rpm dropping started a month ago.

 

[smirn0ff]

for one year I saw 2 times my car doing that. one of the times was when putting the car into "P", but the car was not completely idle. the second time was in the garage, car was cold and A/C was started in seconds.

 

[xsolara]

In your video to the right of tach it shows "D" was you car in drive when this occurred ????
If it was it could be the transmission causing this fluctuation.

 

[Munch520]

Mine does the exact same thing. In neutral and in drive. Dips in the exact same way and at lowest point (of rpm) the car vibrates/hums until rpms pick back up.

It did stop once I turned off the windshield defroster this time...

 

[dakwonhee]

Hi, guys..

Yesterday, finally, the dealer called me for pick my car up with clearing all the issues.

1. Fluctuating Engine RPM and shaking :
- They changed the throttle body. the technician insisted to change it since he witnessed the symptoms when his test driving.

2. Black out screen of back-up camera :
- They replaced the back-up camera and then found the pinched wiring harness.
They replaced it to.

3. the right tail lamp not working :
- They traced all wires and found the bad grounding.

They spent total 7.5 hours to fix all issues and I have used their loaner car for four days.
Now, I just afraid of more issues coming out from my car...I am doubting the quality control and workman ship of Hyundai..

Even I am a Korean-Canadian, I will be hesitating buying another Hyundai car.

But the dealer service is very impressive and excellent...I don't have any issues with the dealer service.

 

[dougmcp]

Don't know what your trouble codes were so it could be anything from a throttle position sensor to a CPU issue to a sticky valve in the transmission. If it does this consistently it's time for another dealer visit.

 

[Munch520]

Wanted to update this thread with my results, my TB wasn't changed but it was cleaned and holy crap what a difference. Idle is perfect (500 rpm once up to temp) and gas mileage has improved a few mpg according to the computer.

My question is, why the heck would the TB be gummed up enough to cause idling issues after only 25,000 miles? I don't think my engine air filter's been changed yet, would that have something to do with it?

 

[Seejay]

Wanted to update this thread with my results, my TB wasn't changed but it was cleaned and holy crap what a difference. Idle is perfect (500 rpm once up to temp) and gas mileage has improved a few mpg according to the computer.

My question is, why the heck would the TB be gummed up enough to cause idling issues after only 25,000 miles? I don't think my engine air filter's been changed yet, would that have something to do with it?

Yes, that's way past time changing. As far as the TB getting gummed up, I can only ask: what kind of fuel do you purchase for the car?

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[xsolara]

Are you using a K&N air filter ?? At one time it was reported that the oil used on the filter caused problems with TB

 

[Munch520]

Yes, that's way past time changing. As far as the TB getting gummed up, I can only ask: what kind of fuel do you purchase for the car?

Well that's embarrassing, usually I'm a stickler for maintenance and I thought when I checked the engine air filter was a 25k or 30k service interval. I'll have to look again

87oct usually

Are you using a K&N air filter ?? At one time it was reported that the oil used on the filter caused problems with TB

No just regular factory filter

 

[Seejay]

Well that's embarrassing, usually I'm a stickler for maintenance and I thought when I checked the engine air filter was a 25k or 30k service interval.

It depends on the service. Dusty conditions or lots of urban mileage can clog a filter quickly with fine particulates. It's very surprising and it greatly affects an electronically controlled engine. It's a shame that checking the filter on these cars is so much a PITA and consumes plastic push pins. At that point, I am inclined to change it, rather than go through the procedure again later. The standard OEM paper filters at the dealer are reasonably priced.

87oct usually

I stay away from regular gas where I live because all the regular fuels available are loaded with ethanol (up to 10% and they mean it!). Friends in the refining business have convinced me that most regular grade fuels are bad news for nice cars. In Houston, it's an extra 50 cents a gallon for premium versus regular, and that's not trivial. But I figure that if I cannot afford fuel at 2.50 USD a gallon, I should not be driving a car like this. But that's me.

 

[jarred52]

Premium fuel does not mean ethanol free. There is a web site, I think it is puregas.org, that lists the stations in each state that sell ethanol free gas.

The EPA mandates the use of ethanol in most areas especially in cities. Unfortunately for me, there are no stations that sell ethanol free fuel in the Dallas area. I've used ethanol free gas in areas where available and my Genny does get noticeably better mileage; using premium fuel with ethanol has shown no difference than regular in three separate trials. No matter which fuel you use, always use one that is "top-tier" rated.

 

[AustinTX]

The EPA mandates the use of ethanol in most areas especially in cities. Unfortunately for me, there are no stations that sell ethanol free fuel in the Dallas area. I've used ethanol free gas in areas where available and my Genny does get noticeably better mileage; using premium fuel with ethanol has shown no difference than regular in three separate trials. No matter which fuel you use, always use one that is "top-tier" rated.

This!

I have tried premium fuel in my 3.8 V6 on several occasion, and there is no measurable difference in performance (I did about 15 different 0-60 runs on a closed track with a CAN bus data recorder attached, using different brands of gas - Shell, COSTCO and Valero) or miles per gallon - none. All my fuel consumption data is available on the fuelly link in my signature, so anyone can check this out for themselves based on actual real data, not trip computer information or anecdotal evidence.

Ethanol information can be found here: http://www.eia.gov/tools/faqs/faq.cfm?id=27&t=10 This is a government website, so check it out before Trump decides he doesn't like their science either and removes the information from the public eye.

And some more in depth information here: https://www.bellperformance.com/blog/bid/110140/Does-premium-gas-have-ethanol-in-it

In most states, ethanol is required by law, no matter if premium or regular or mid-grade ... Apparently including Texas...

 

[Mark_888]

In some locations, stations near marinas are allowed to sell gas without ethanol, because many marine engines cannot handle it.

 

[Seejay]

Actually, premium fuel may mean more ethanol, not less. You have to know someone who works at the refinery who will tell you they are doing with their retail fuel blends and their distribution area.

 

[Munch520]

It depends on the service. Dusty conditions or lots of urban mileage can clog a filter quickly with fine particulates. It's very surprising and it greatly affects an electronically controlled engine. It's a shame that checking the filter on these cars is so much a PITA and consumes plastic push pins. At that point, I am inclined to change it, rather than go through the procedure again later. The standard OEM paper filters at the dealer are reasonably priced.


I stay away from regular gas where I live because all the regular fuels available are loaded with ethanol (up to 10% and they mean it!). Friends in the refining business have convinced me that most regular grade fuels are bad news for nice cars. In Houston, it's an extra 50 cents a gallon for premium versus regular, and that's not trivial. But I figure that if I cannot afford fuel at 2.50 USD a gallon, I should not be driving a car like this. But that's me.

Gotcha, I'll just grab a nice one at autozone.

Interesting I just filled up here in Ohio and 87 is $2.36/gal while 93 is $2.96/gal. ($300 annual variance based on my driving)

While I agree with the sentiment as far as "what's a few cents extra when you own a car like this", if I applied that thinking across the board I wouldn't have bought my first house at 25 and I wouldn't own this car now one of the many reasons I think this is the best deal out there is bc I thought I could get away with 87oct (compared to the 535, GS, e300, etc)

 

[Mark_888]

Gotcha, I'll just grab a nice one at autozone.

Interesting I just filled up here in Ohio and 87 is $2.36/gal while 93 is $2.96/gal. ($300 annual variance based on my driving)

While I agree with the sentiment as far as "what's a few cents extra when you own a car like this", if I applied that thinking across the board I wouldn't have bought my first house at 25 and I wouldn't own this car now one of the many reasons I think this is the best deal out there is bc I thought I could get away with 87oct (compared to the 535, GS, e300, etc)

Try mid-grade (or fill 1/3 premium and 2/3 regular to save a bit). I have found it makes a difference in my G1 Genesis 3.8.

 

[cane2025]

Is getting a TB cleaning part of the 22,500 suggested service? I just put some fuel additive in the car, changed the air filter and changed the engine oil and filter. Should I have the TB done too?