Author Topic: rough/ intermittent/ irregular idle (misfire???)  (Read 249 times)

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  • Posts: 23
  • gb United Kingdom
    Leicester, UK
Hello to everyone!
Seeking the wisdom of the forum and suggestions. About half-year ago started to notice that a strange behaviour in engine work while on idle. Here are the list of simptoms which started at about 60k miles:

 - only happens when the engine is fully at operational temperature (never on cold or below 90 degrees C)
 - car starts without any issues, always, in hot or cold weather. (it was -12 here in UK for a bit, no issues)
 - revs gauge shows a slight dip and jump on idle (sometimes from 500 - 900 rpm)
 - increased vibration from engine (feels inside the car)
 - "wrong sound" of idling diesel engine
 - feels like a misfire, irregular work of engine
 - whilst driving the car behaves without any issues, engine pulls like a dream!
 - no smoke visible (DPF fitted), no abnormal smells
 - can happen any time, without any logical trigger  :crazy1:- can be absolutely normal for a month, but can be happening many times per day, or several times a week

 As far as I was reading some other forums in search for the answer I've came with a few guesses : crankshaft position sensor or/and fuel rail pressure sensor going nuts; several different issues with high pressure fuel pump, which could range (in repairs cost) from 50 to 500.

Has anyone else experienced similar issues? What are the solutions to it? 
The car still has got manufacturers warranty till February 2019, I am planning to go Hyundai with this issue soon. But like I said it can come up at any time or it can lay dormant for weeks not showing any signs. And HY charge 95 per hour for investigation.

The patient is serviced reguarly (last was at HY, 60k miles major service, all filters changed, then extra oil change at 67k miles), had undergone an engine carbon clean at about 55k miles. Had 3 bottles of Wynn's diesel fuel system and injector cleaner fluid since then. 
2014 1.6 CRDi 128hp, 73k miles

Here's a link :link: Hyundai i30 1.6 CRDi 128hp rough intermittent idle - YouTube  of the problem (mostly it can be heard, camera doesn't capture the irregular vibrations that good):
Cheers!


  • 2014 1.6 CRDi 128hp Style "Cream"

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  • Posts: 7,674
  • au Australia
    Perth
  • 2013 i30 GDi SE 3dr, 1.6 Ltr Petrol, 6 Spd-M
Re: rough/ intermittent/ irregular idle (misfire???)
« Reply #1 : July 07, 2018, 10:06:29 »
If everything is running fine and only noticeable at idle then maybe it's just the thermo fan cutting in :undecided:

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  • HOS BOSS
  • Posts: 24,820
  • england England
    Wirral
  • Wirral, UK. - 1.4 Petrol Active - Aqua Blue
Re: rough/ intermittent/ irregular idle (misfire???)
« Reply #2 : July 07, 2018, 10:55:37 »
Have you considered/altering idle rpm's and see how it goes.

Re charge
As still under warranty get it back to dealers to check out.

Should be nil cost plus once it is logged then it is recorded on the system until resolved.

Sent from my ATU-L11 using Tapatalk

  • 1.4 Petrol Active       I'm no expert, so please correct me if I'm wrong

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  • Posts: 1,815
  • au Australia
    Samford Valley
Re: rough/ intermittent/ irregular idle (misfire???)
« Reply #3 : July 08, 2018, 02:21:53 »
Another suggestion only, one injector is misbehaving. At higher Revs the effect of the inefficient one is smoothed by the other 3
  • Every FD model; BMW Z3 M; Mitzi Magna(mobile office)

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  • Author
  • Posts: 23
  • gb United Kingdom
    Leicester, UK
Re: rough/ intermittent/ irregular idle (misfire???)
« Reply #4 : July 09, 2018, 17:19:08 »
If everything is running fine and only noticeable at idle then maybe it's just the thermo fan cutting in :undecided:

Hm...Thermo fan? I believe that could cause a dip in revs once (like after switching on AC or rear demister,or lights), but should return to normal idle after. Looks like it's a task for HY to find out what demon possessed the engine.
  • 2014 1.6 CRDi 128hp Style "Cream"

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  • Author
  • Posts: 23
  • gb United Kingdom
    Leicester, UK
Re: rough/ intermittent/ irregular idle (misfire???)
« Reply #5 : July 09, 2018, 17:22:51 »
Have you considered/altering idle rpm's and see how it goes.

Re charge
As still under warranty get it back to dealers to check out.

Should be nil cost plus once it is logged then it is recorded on the system until resolved.

Sent from my ATU-L11 using Tapatalk

Ehm...not really sure what do you mean by altering the idle rpm. You mean just revving up a bit while in neutral? Or...?
Yeap, going to HY soon. Let them sort it out, although it's one of those things where they'll take the car for a spin around the block and the engine will behave as normal. And as soon as I get it back it'll start playing up again...Maybe the video will convince them to investigate until they actually find the cause?
  • 2014 1.6 CRDi 128hp Style "Cream"

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  • Author
  • Posts: 23
  • gb United Kingdom
    Leicester, UK
Re: rough/ intermittent/ irregular idle (misfire???)
« Reply #6 : July 09, 2018, 17:35:01 »
Another suggestion only, one injector is misbehaving. At higher Revs the effect of the inefficient one is smoothed by the other 3

That was on my mind. Still, logically thinking it should be playing up on idle all the time, and not just when it's in a bad mood, or why the hell it's doing it anyway.
Still, a possibility. I'm guessing HY should send the faulty injector for a refurb (if that's the fault), or replace with a new one.
A proper injector test will definitely show if there's an issue, but I doubt that HY will be willing to take off all 4 injectors, send them for a specialised test.
I believe that GD model CRDi engines have got Bosch injectors fitted. And one place I've found in my city charge 25 per injector.

:link: Hyundai i30 Diesel Fuel Injectors
  • 2014 1.6 CRDi 128hp Style "Cream"

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  • Posts: 1,815
  • au Australia
    Samford Valley
Re: rough/ intermittent/ irregular idle (misfire???)
« Reply #7 : July 09, 2018, 18:25:23 »
You are correct, switch of A/c and the like done with the cooperation of the ECU which will alter RPM to compensate.

"Have you considered/altering idle rpm's"?...... that's simple just twist the screw thingy on the carburettor. :mrgreen:
 
Eventually, the alleged intermittent injector would probably fault permanently. If I were there I would be checking electrical connections especially to the injectors, look for corrosion  and use WD40.
The Common rail system on all the i30s is Bosch . For optimum performance the ECU should be remapped to the codes on each injector.
Hy are going to screw you, so I would look for an independent mechanic who has a few years in the trade, to advise you. Remember we are all just guessing at this stage.  :goodjob2:
  • Every FD model; BMW Z3 M; Mitzi Magna(mobile office)