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RPM inconsistent at idle

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alastairm

New Member
Jul 14, 2020
18
15
3
Finland
Hey,
Seems I might have another engine issue. 2 years ago a spark plug went even right after being serviced, had engine misfires and check engine light, but once repaired everything was perfect.

A few days ago i noticed when sat at traffic lights that the idle felt a bit rough with some vibration coming from the rear. It didn't happen for the next few days so I thought nothing of it. But today when driving home, the RPMs are wobbling all over at idle and it sounds like the engine is choking to some extent. A similar sound from what I remember before the spark plug died 2 years ago. The car was serviced in December so I'm quite annoyed if there's another thing wrong with the car. There are no error lights on the dash and the car starts perfectly.

The roads were so bumpy from melting/freezing snow today that I couldn't tell how the car felt when driving on the motorway. It seemed maybe smoother between 1-2.5k RPM but anything over maybe had some lurching feeling. No backfires I think, but the road noise from wet snow was so loud, I'm not sure.

I planned to go a trip this weekend but it seems that is off the cards, don't want the engine to die on me.

Any clues what could be wrong?

tried to record the idle wobble, neighbours dog wouldn't stop effing barking though https://streamable.com/ws80lr
 
Last edited by a moderator:
It's more pronounced in N or custom (with the exhaust on sport), but it does still occur in normal mode albeit less noticeably
 
Jajodu said:
I would have thought that the hpfp would effect the engine under load rather than idle.
Click to expand...
from what I've discovered over the past 2 weeks. If you get inconsistent idling, rough sounding like misfires etc. then its the HPFP.
 
alastairm said:
Hey,
Seems I might have another engine issue. 2 years ago a spark plug went even right after being serviced, had engine misfires and check engine light, but once repaired everything was perfect.

A few days ago i noticed when sat at traffic lights that the idle felt a bit rough with some vibration coming from the rear. It didn't happen for the next few days so I thought nothing of it. But today when driving home, the RPMs are wobbling all over at idle and it sounds like the engine is choking to some extent. A similar sound from what I remember before the spark plug died 2 years ago. The car was serviced in December so I'm quite annoyed if there's another thing wrong with the car. There are no error lights on the dash and the car starts perfectly.

The roads were so bumpy from melting/freezing snow today that I couldn't tell how the car felt when driving on the motorway. It seemed maybe smoother between 1-2.5k RPM but anything over maybe had some lurching feeling. No backfires I think, but the road noise from wet snow was so loud, I'm not sure.

I planned to go a trip this weekend but it seems that is off the cards, don't want the engine to die on me.

Any clues what could be wrong?

tried to record the idle wobble, neighbours dog wouldn't stop effing barking though https://streamable.com/ws80lr
Click to expand...

To me it sounds like you barely push her each day or at least not even once a week.
could be a built up of resedues.

The misfire is fixed as you said,the fuel pump should still work on your 60k Car.
Not sure what fuel you choose too and from what gas station.

What about the Oil you use?? I use 0W-30
As well as do "Floor it Friday" where I drive my car up to 7k RPM on my way to work.

Let me know bit more of the car as I am a retired car mechanic
 
NeroMastic said:
What about the Oil you use?? I use 0W-30
Click to expand...

Whiteout wanting to deviate the discussion out of subject, out of curiosity, what are the cases where the oil type can cause misfires ?
 
nicosp said:
Whiteout wanting to deviate the discussion out of subject, out of curiosity, what are the cases where the oil type can cause misfires ?
Click to expand...
There are no misfire's caused by oil
What I am trying to figure out is they use of oil and see potentially how well it can lubricate
As alastairm said : "the RPMs are wobbling all over at idle and it sounds like the engine is choking to some extent"
Either the Oil seems to not lubricate
or Carb Resedue is building up on inside.

My apologised in advance as my intention are just to help in theoretical probleme solving
English isn't my native languge either and my skills to use forums is still advancing at a Benz Patent Motorcar pace.
 
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If there is enough oil and it is a standard, Hyundai provided oil, then no, its 100% NOT the issue.
Most likely somewhere on the intake side - air filter, hoses, vacuum lines, spark plugs or fuel pump / injectors.

After all of the above is crossed out, only then id start worrying about "not enough lubrication" (which doesnt even cause issues like that, but whole other issues).
 
xzstnce said:
If there is enough oil and it is a standard, Hyundai provided oil, then no, its 100% NOT the issue.
Most likely somewhere on the intake side - air filter, hoses, vacuum lines, spark plugs or fuel pump / injectors.

After all of the above is crossed out, only then id start worrying about "not enough lubrication" (which doesnt even cause issues like that, but whole other issues).
Click to expand...
Sensors can also lead towards the issue too.
A OBD tool could help out to see.
Electronically everything can be easily identified.
But what can't be seen is the biggest problem usually.
Clogs,leaks,residual built up can all cause various parts to not work or be out right damaged.
The oil can be one of them,but its the easiest to faze out of the problems tab.

It's up to the owner what and how they use they car.
 
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