Kia Rio Hesitation when changing gear

[Stanky]

Mrs_Stanky has a Kia Rio (2004, 1.3 powerhouse) which I drive occasionally and notice an annoying momentary loss of power when changing gear or pulling away from stationary.

 

I have googled this and the only suggestion I could find was that the HT leads and plugs should be changed, now I changed the plugs at its last service <2000 miles ago and the old ones looked fine, light brown tips, not too big a gap between the electrode and the prong thing. the HT leads were not changed, but I would have thought that dodgy leads would manifest themselves all through the rev range, not just when pulling away or changing gear?

 

the symptom is almost like the car is momentary flooding itself when you apply the accelerator, it momentarily bogs down, then clears its throat and behaves normally. During normal driving it is fine, no misfire, expected power and torque from 1300cc 8v motor, just this odd bogging down. It also does it between 2nd and 3rd gears, when the gear engages there is a momentary hesitation before the power goes down.

 

Its not a problem really for her, but i tried to nip out quickly into a gap in traffic and it suddenly bogged down which caused a minor touching cloth moment before it picked up and went like it should. Mrs_Stanky isn't known for her decisiveness in traffic, she'd wait for a bigger gap in the traffic then pull out sedately.

 

Now, this is really just a minor annoyance currently, but I'd rather it didn't develop into something more frustrating. When this happens the revs don't rise, so I'm fairly sure its not the clutch giving up and slipping, though last time I put it up on ramps the clutch emitted a horrific burning smell, so I wont rule out that its had a hard life transporting the previous elderly owners dogs around and is due a replacement. 

 

Any suggestions of what to check? A dose of carb cleaner down the throttle body? Might the butterfly be a bit gummed up and its sticking in the 'closed' position? I wondered about this but thought it would likely cause other problems beyond this momentary hesitation.

 

Finally, this is very very momentary. Long enough to think 'shit its about to stall' before it clears itself and drives absolutely normally. Also only seems to happen when the engine is cold.

 

(And yes, I know OMG ALL NEW CARZ IZ SHIT)

 

[twosmoke300]

If its got a motorised throttle body then it could be sticking due to carbon build up . Open it nice and slowly so as to not damage the gears/motor and clean the venturi with some alcohol/brake cleaner/ carb cleaner .

 

Its free so would be a good place to start , worth doing anyway to save future damage to the throttle body workings. If its got a normal thottle cable to butterfly setup then you would probably feel the extra pedal effort needed to break it free.

[phil_lihp]

Interesting actually, my 2012 C'eed 1.4 does the same thing sometimes, it went through a phase of being quite annoying but sorted itself out after a long motorway journey and hasn't done it since so I assumed it was a combination of too many short journeys and not being revved - I tend to drive like a taxi driver and don't thrash my cars which I've been told the Kia engines don't like.  It does seem to do rather better MPG when driven harder which admittedly doesn't make much sense.

 

Another thought, have you put premium unleaded in it?  I had a tankful of BT Ultimate in mine during the worst of the issue which gave it better performance and economy but wondered if perhaps it was confusing the ECU.  That said, never had a problem before. 

[tooSavvy]

Giving my Savvy a good spanking (exploring the far edge of the rev counter) it always has/does 'hold' revs when lifting the pedal to change up... "they [really!!] all do that, sir".

 

As the throttle is Fly By Wire... it is controlled by the ECU and it has something to do with 'latency', that is when you snap the throttle OPEN, to 'light up the tyres', the sensible ECU eases open the TB <momentarily> to reduce Hcarbon emissions.... and it is evident when snapping a change, too!!

 

 

TS

[Stanky]

Thanks Phil and TS,

 

Phil, in answer to your point, Mrs_Stanky does indeed drive it practically exclusively within a 10 mile radius of Stanky_Towers and doesn't believe in revving an engine. I, on the other hand, feel that a modern engine likes to be given a bit of a thrash every so often. This may be why it seems happier after I've taken it out for a drive as I do hold on to gears longer than she does.

 

We run it on Shell regular (or fuel saver or whatever they call it) and occasionally - when its been reduced at tesco - give it a sip of redex too. 

 

TS, to respond to you - that makes a lot of sense, bloody ECU! It does feel like the TB isn't opening fully when I'd expect it to, but does almost immediately open as soon as the 'hang on a minute' thought has gone through my brain. My Almera TB is controlled by a bit of string from the pedal to the TB and so the response I am used to is instant, at least it is now I've adjusted the 3" of slack out of the throttle cable. 

 

The Rio is a bit of a tough one to really thrash as it is 'L' spec which means the bourgeois luxury of a rev counter was not included, I suspect that even when I'm 'giving it the beans' its rarely touching 4000rpm. Not too keen to bounce it off the limiter but will endeavour to take it out for a longer trip soon and/or give it a razz about every couple of weeks. It needs a wheel bearing doing so long journeys have been the preserve of my Almera for the last 18 months, which may be why this issue is beginning to manifest itself now.