[antandand]

Hey Guys!

I've had my i30 1.6 crdi premium automatic for a few months now (7000 miles) and there's something thats been niggling at me.

When I drive off the rev counter increases and drops a little as it changes gear, but when I stop accelerating and take my foot off the accelerator pedal, sometimes the rev counter will slowly decrease as the car slows but a lot of the time it will immediately drop to 900 rpm.  Then when I accelerate again, the revs shoot back to where they should be and continue to rise as i accelerate.

It seems like the engine is being 'disengaged' somehow.

The only thing I can think of is perhaps it does it to increase fuel economy but thought I'd ask here to tap into your vast knowledge on the subject.

Thanks in advance

Tony

[Dazzler]

Welcome Tony .. No other Premium CRDi owners have mentoned that but hopefully a couple may spot the thread and comment...

I changed the title to attract more replies...

[Phil №❶]

Not sure what age your car is, but if the engine is at idle you are essentially coasting and not receiving any engine braking at all. This is not a good idea, down hills you will only have your brakes to slow you. When you accelerate, is there a thump, jerkiness or any other strange happenings.

[antandand]

Thanks for the really quick responses.

I hadn't thought of the engine breaking side of things but you do make a good point.

I bought my i30 5 months ago when it was 8 months old and only had 30 miles on the clock (it now is closer to 7000).  It had been sold to a company who then went under and the car just at there for 8 months.

I look forward to hearing more responses but at the moment I think i'll pop into the dealer on the weekend to run it by them.

[antandand]

Sorry, forgot to mention that there isn't any strange bumps when accelerating.

The only thing I notice is that when I first accelerate gently, the engage makes a noise like tappets banging but if I accelerate faster then it is a much smoother quieter noise but obviously uses more diesel.

[Phil №❶]

BTW, Welcome to the forum antandand 

[Talking Hoarse]

Hi Tony
I see the car is now just over a year old so has had its 1st service - did you ask at the dealers?
You have me thinking about the behaviour of my CRDi auto (UK 2011 spec) - it does provide a (very) limited amount of engine braking when you lift off the accelerator, however below a certain speed (dont ask me what) it does seem to disengage drive, ie freewheel & the engine drops to idle.  Thats no bad thing (to improve the mediocre economy I guess) but needs some care when you want to accelerate again eg round a hazard /corner etc - as the power takes a moment or 2 to return (spool up?) and that can also result in an inelegant lurch when it does.  Answer is to anticipate the power need - maybe dare I say left foot brake or heel & toe a little?
As far as the freewheeling /engine drops to idle feature - I am privileged as my car is on its 2nd auto gearbox.  I think both have behaved about the same as far as this feature, maybe the new gearbox frreewheeling slightly more noticable than the old (therefore faulty) unit.
So drive it and enjoy it - if you have concerns shout out here or go to your dealer.
Ed

[Phil №❶]

Forgot to ask antandand, what speed is the disengaging happening at. 

[Doggie 1]

BTW, Welcome to the forum antandand 

 

[antandand]

Sorry for my delayed response.

I've still not had the time to go to the dealer yet to ask them about this but i've been paying a bit more attention to it and have found that it only occurs when the auto is in effect in 1st or 2nd gear.  When it changes up to the equivalent of 3rd gear the revs stay the same when I come off the accelerator so it's only on speeds up to about 30mph for me.  I haven't noticed any lurch when coming back on the accelerator.  It seems to be smooth enough.

I'll post back when I get a chance to swing by the dealer to ask them about it

[Phil №❶]

@ Kom or Pip,

Based on the last response, my GUESS would be that at such low speed, the auto is not at full pressure and coming off the throttle is interpreted as a request to stop or slow down, so the trans proceeds to disengage the wet clutches and the engine returns to idle. Otherwise the engine would labour and threaten to stall wouldn't it. 

It's well beyond my knowledge but from the description it appears to act as though the gearbox drops back to neutral. Well I don't think this should happen. If that happened there would be no "creep" if the brake was released when stopped. Is there?

[Talking Hoarse]

Reading this thread got me trying this out, watching & listening etc in my car.  My car does go into "freewheel" (ie no noticable engine braking & revs drop to 900) commonly when decelerating from about 20mph, but sometimes from higher speeds - I noted it did it once when going down a hill at 40ish mph.  And yes it still creeps when it gets to a standstill despite "freewheeling".
However as long as the car drives smoothly and finds the right gear fairly promptly when required I dont see this as a fault - at least not yet.
Ed

[komaterpillar]

On my phone so can't go into detail, but, google "sprag clutch" most torque converters have them 

On my phone so can't go into detail, but, google "sprag clutch" most torque converters have them 

I haven't even bothered to google yet 'cause I just know I'm going to find my understanding was outdated! I've never seen the insides of an auto box so should have pulled my head in.

I have however dismantled and rebuilt manual and transaxle boxes and I drive these for preference partly 'cos I know they are simple even if complex (Irish there) and simplicity = reliability and partly because I'm in control of basic functions.

I'm going to withdraw now lest I look more foolish.

[komaterpillar]

Mate I reckon it's good to get another persons take on a subject even if you don't necessarily agree, because they may see a problem in a different light to the way that you do yourself and may pick up on things that you've overlooked. I love getting other peoples take on things. 

[Phil №❶]

Kom's right Pip, it's all part of the discussion, that's how we learn. Difference between a forum and a classroom really, you're allowed to be a bit incorrect.

I'm always asking Kom about things if I'm not sure, if that makes me look stupid, so be it.

Your input re oils is always spot on IMO. 

[komaterpillar]

Difference between a forum and a classroom really, you're allowed to be a bit incorrect.

Your input re oils is always spot on IMO. 

 

[i30niko]

Hey Guys!

I've had my i30 1.6 crdi premium automatic for a few months now (7000 miles) and there's something thats been niggling at me.

When I drive off the rev counter increases and drops a little as it changes gear, but when I stop accelerating and take my foot off the accelerator pedal, sometimes the rev counter will slowly decrease as the car slows but a lot of the time it will immediately drop to 900 rpm.  Then when I accelerate again, the revs shoot back to where they should be and continue to rise as i accelerate.

I had this problem as well - IT was my first post in this forum when I was a newbie!! Its how the car is designed - You learn to live with it. Once you are used to it you can control the throttle pedal and you can 'anticipate' the change..

It seems like the engine is being 'disengaged' somehow.

The only thing I can think of is perhaps it does it to increase fuel economy but thought I'd ask here to tap into your vast knowledge on the subject.

Thanks in advance

Tony

I think you are describing the Turbo .......Mine does that aswell. It is also the combination of the gearbox.
Sometimes it holds onto 3rd gear so the revs do not drop while cruising. Remember that the Turbo kicks in on high
revs as well.....What you are describing as being 'disengaged' is the turbo and the gear change which usually occur at the same time.
As soon as you go above 60km/hr leave the throttle you will feel the 4th gear kicking and the revs immediately drop into idle.
I hate that aswell. The gearbox ratio should be different for the diesel, but they have just stuck it in unchanged.

[antandand]

Hey guys!

I've finally found the time to get my car booked into the dealer to investigate this issue.  The main reason was because it's started happening at higher speeds now (revs drop to idle when going 65mph but only within first 5 minutes of driving the car from cold)

They said it's working as designed in the lower speeds and it doesn't drop back to idle at higher speeds so that the revs are available for overtaking.  He side stepped the question when I pointed out it was doing it when cold at high speeds.

He also mentioned that even though the revs drop to idle the engine is still engaged and providing engine breaking which I find hard to believe.

Not a really good answer but I guess it'll have to do.

Thanks for all your input on this.

Tony

[Phil №❶]

You need a better dealer IMO.