Leon high and low idle issue...

[ultima84]

So today my Leon Cupra T (57 Plate) has shown a idle issue. I not that it has been discussed before but I can't seem to find specifics.

So if I start the car and let it idle it idles roughly between 650 to 850rpm rather then the normal stable 1200. If I then drive the car and revs under 2500 is seems to try and judder and still adjust the rpm. Once over 2500rpm it seems to drive ok except if i come off the throttle fully it seems to 'hang' then a second later slow down.

The only final difference is once it has been driven when coming to a stop it idles at 1800ish rpm. If I then sit in traffic for a time it creeps back to idling at 650 to 850 rpm.

I unplugged the sensor that is top left on top the engine when standing at the front of the car looking into the engine bay but removing it and reattching made no difference to the idle. I'm assuming this was an air sensor though half dark so hard to see exactly.

Help appreciated!

 

[Smee]

850 to 650 is normal for my cupra

 

[ultima84]

Deffo not to mine, I've had it 3 years and never had it idle this low since the day I got it. For me its deffo got rough on idle.

When we idles between the 650 and 850 rpm it is close to stalling...to the point the lights dim etc where it is struggling to keeping the engine going so deffo not right.

 

[Smee]

video?

 

[ultima84]

Video here

youtu.be/upvPij8t3qo ...........you will need copy and paste this to the address bar...i cant add the full address due to restrictions.

Not ideal as off phone but is u have volume up you can hear the engine juddering around while the idle sits there bouncing about.

 

[Smee]

http://www.youtube.com/watch?v=upvPij8t3qo&feature=youtu.be

reposted for you for ease... that is ODD!!!! sounds like a small bang. when you Rev it is it fine???

 

[secret.squirrel]

Going for the obvious, if you have access to VAGCOM through someone, plug it in and see if its throwing up any codes?

Squirrel.

 

[ultima84]

So the engine revs fine, when u apply the throttle there's no lack of response. The only thing if I hold constant throttle at say anything under 2500 it still tries to judder around the revs, over 2500 is fine....

Maybe air flow sensor or idle control sensor if it has one?

 

[ultima84]

I don't no anyone with it myself but in Guildford area if anyone no's of anyone with the software to plug in...

 

[Smee]

im thinking coilpack might be showing signs of wear but im not mechanic. im sure Kev will be along soon

guildford i have no idea who is in that area. might be worth putting a post up in Vagcom section for help.

 

[ultima84]

I'm hoping not coil pack as it drives fine and doesn't seem to have the idle issue over 2500rpm so on motorway etc and general driving you'd never tell really,

Thanks for your help thus far!

 

[secret.squirrel]

Anyone know if these engines have a mechanical throttle cable or is the throttle "fly-by-wire"? If its a cable, could be that the cable is dragging on the way back down causing the slow decrease from 1800rpm downwards.

As for the idle issue I'd say have a look at the air flow sensor, seems if its running fine above 2500 rpm, then its running fine on boost (assuming a boost threshold roughly around that figure). Failing that, idle sensor, failing that something to do within the ECU for which you will need VAGCOM.

Squirrel.

 

[secret.squirrel]

Any sign of the CEL at all as well mate?

Squirrel.

 

[Smee]

well isnt the test for the fault MAF to simple disconnect it??

lee

 

[ultima84]

CEL sorry? What's this? And don't think its got a throttle cable, think its fly by wire, and where is the MAF sensor? Only sensor I seen if on the top of the engine on the top left corner, as I say dark so no ideal for looking

 

[Smee]

top left corner of enginer cover is the MAF

unplug it see if it gets better i believe is the test but not 100% sure

 

[ultima84]

So I did that earlier and unplugging it made no difference, not sure if that means it was failed and stay failed when it was disconnected or if it should have gone to a default value and made it better when disconnected...

 

[Marshall]

This seems more like an air leak most probably by the pcv valve.
When its idling what happens if you remove the oil cap?
Does it try to stall or does it not make any difference?

 

[ultima84]

So ok just did this test.

The car is now cold so when it started it was a lot smoother idle but left it for a minute and being a bit warmer made the idling worse.

Anyway once it was idling as shown in the video linked above i removed the oil cap and there was a very slight suction (prob the wrong word) which tries to keep the cap in place. I mean a slight suction as well, noticeable but not strong.

Once the cap was off the idle rate decreased, i mean the rpm still dropped between 650 to 850 rpm but the time to get to each end of this range much slower and more laboured. When the cap was back on the car idled between the 650 to 850 range much quicker.

 

[Marshall]

If it makes a difference and has vacuum trying to suck the cap back on that sounds ok.

Are you running standard engine cover or an aftermarket air intake?