Seat Leon 1.6 16v (04 plate) - Rough Idle/Stalling once warm

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Tue 20 May 2014 00:09
Seat Leon 1.6 16v (04 plate) - Rough Idle/Stalling once warm - iajb

Hi,

I have recently developed a problem with my 2004 Seat Leon 1.6 16v. From cold the car runs fine and I can drive it perfectly well. However, after around half an hour or when the car has warmed up it becomes nearly undriveable around town/moving off.

Once warm the idle suddenly becomes very low, so much so that you can hardly hear the engine it is that quiet, the engine will idle rough and rev up and down all on its own. Thats not the real problem...when I attempt to drive as normal the car rattles/shakes when moving off and just wants to stall constantly over and over again. Its literally left me stranded in the middle of roundabouts countless times, I give it more revs to prevent stalling yet moving off feels very laboured and the engine just wants to die.

I brought the car in February this year, it has tax till October and MOT till Jan 2015. With the clutch on the way out (very high bite), brakes needing to be replaced and a massive chip in the windscreen I am sadly thinking of getting rid already :(

Any ideas on what is causing the rough idle/stalling once engine is warm? If I could fix that problem that would be a great start.

Thanks in advance and sorry for such a long post!

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Tue 20 May 2014 08:32
Seat Leon 1.6 16v (04 plate) - Rough Idle/Stalling once warm - elekie&a/c doctor

First thing to do ,would be to get it plugged in to a diagnostic tester to check for any faults logged.From your description ,I would think that the engine coolant temp sensor is sending the wrong info to the engine ecu,and thus overfuelling.A very common problem on vag cars,and not difficult or expensive to fix.

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Tue 20 May 2014 08:38
Seat Leon 1.6 16v (04 plate) - Rough Idle/Stalling once warm - The-Mechanic

Don't worry about the long post mate, it's better to have the information on a fault rather than the usual "my engine light has come on, what is the problem"

If yours is OK cold but not when hot, I'd be looking at the coolant temperature sensor first. Ideally, get the car plugged into a diagnostic scanner and read the actual values of the coolant temp. If the sensor has failed it can lead to a false signal to the ECU making it believe it's colder than it really is, therefore it will richen the fuel mixture (a bit like pulling the choke out on an old car), causing the sort of symptoms you are getting.

LOL, my long post meant ac doc got in before me...

Edited by The-Mechanic on 20/05/2014 at 08:40

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Tue 20 May 2014 10:43
Seat Leon 1.6 16v (04 plate) - Rough Idle/Stalling once warm - iajb
Thanks for both the replies in this thread.

I could get a diagnostics cable off eBay for under £10 and read fault codes on my laptop if needed using that VAGCOM program, but my local garage guy is pretty easy going so might pop it up to him he usually would check things like this for free.

Could the temp sensor issue explain the bad mpg I've been getting, around 25mpg?
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Tue 20 May 2014 13:24
Seat Leon 1.6 16v (04 plate) - Rough Idle/Stalling once warm - A3 A4

Same engine in my A3 which had the same faults, fixed by replacing the temperature sensor, easy fix £7 off Ebay, make sure you get the right one, the part number is on the old one.

I know what you mean about the idle, the car was a nightmare to drive. As stated above the sensor can give a myriad of faults and affect MPG.

I also bought a diagnostic reader for £15 which I needed to clear the engine light on the dash.

Found a YouTube guide to replacement on a similar Golf.

www.youtube.com/watch?v=bfIYdalV2cQ

Edited by A3 A4 on 20/05/2014 at 13:31

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Tue 20 May 2014 14:08
Seat Leon 1.6 16v (04 plate) - Rough Idle/Stalling once warm - iajb
Thanks for that YouTube link mate really helpful! Will definitely get the part and attempt this myself looks pretty easy.

Yes it is a nightmare to drive and I only passed last December so I presumed it was driver skill at fault first but I knew there was something wrong.

Apart from the obvious like wait till the engine/coolant is cold before fixing, is there any way to minimise coolant leak, will it gush out when you remove the sensor?
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Tue 20 May 2014 15:09
Seat Leon 1.6 16v (04 plate) - Rough Idle/Stalling once warm - elekie&a/c doctor

Wait for coolant to get cold,unscrew coolant cap to release pressure,then do up cap again.This will reduce the coolant loss.Also fit a new o ring onto the sensor before fitting into the plastic housing,and also,try not to drop the locking circlip.

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Tue 20 May 2014 20:57
Seat Leon 1.6 16v (04 plate) - Rough Idle/Stalling once warm - iajb
Thanks for all the help. I've ordered the correct part off eBay which came with a O ring and circlip/C clip, should be here later this week.

I will open the coolant reservoir before attempting to replace the sensor although it's a snap shut lid rather than a screw on I think - same principle?

One more question - if the coolant requires topping up can you add different coolant to the existing one or will it all need flushing and refilling? I don't know which brand the garage used on my full service the other month.

Hope I don't sound too clueless!
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Tue 20 May 2014 21:28
Seat Leon 1.6 16v (04 plate) - Rough Idle/Stalling once warm - elekie&a/c doctor

If you are quick enough with the change,there will be little coolant loss.Your car will probably be filled with the pink long life coolant antifreeze which most car makers now use.The system will not need flushing or refilling.Just a little trade tip;take the old sensor out with the connector still attached,makes the wiring connector much easier to remove when it is out of the way of all the pipework.hth

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Tue 20 May 2014 23:12
Seat Leon 1.6 16v (04 plate) - Rough Idle/Stalling once warm - A3 A4

Don't forget to report back!

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Wed 21 May 2014 01:28
Seat Leon 1.6 16v (04 plate) - Rough Idle/Stalling once warm - iajb

Don't forget to report back!

Will do dont worry! Thanks to everyone for the input so far.

Once changed will the car require a decent run to get everything to settle or should I expect an instant fix? I noticed today that the idle was rough even when starting cold, although the drive was nowhere near as affected compared to when its warmed up.

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Thu 22 May 2014 17:59
Seat Leon 1.6 16v (04 plate) - Rough Idle/Stalling once warm - iajb

Lets just say that went badly wrong lol!

Took the old sensor out but it had no O ring on so I was confused and put the new one in its place, but it didnt seem to fit that well. I thought nothing of it as the C clip seemed to hold it all tight in place.

Turned the engine on and lost all my coolant in about 10 seconds. Was very confused until I realised that the old sensor O ring must have been stuck inside the housing and thus preventing the new sensor creating a seal.

Who would have thought its possible to cock up such an easy job! Got to go buy coolant and refill tomorrow now so just wasted 20 odd quid trying to do it myself, had to laugh as I got soaked in the rain as well.

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Thu 22 May 2014 18:08
Seat Leon 1.6 16v (04 plate) - Rough Idle/Stalling once warm - iajb

Lets just say that went badly wrong lol!

Took the old sensor out but it had no O ring on so I was confused and put the new one in its place, but it didnt seem to fit that well. I thought nothing of it as the C clip seemed to hold it all tight in place.

Turned the engine on and lost all my coolant in about 10 seconds. Was very confused until I realised that the old sensor O ring must have been stuck inside the housing and thus preventing the new sensor creating a seal.

Who would have thought its possible to cock up such an easy job! Got to go buy coolant and refill tomorrow now so just wasted 20 odd quid trying to do it myself, had to laugh as I got soaked in the rain as well.

Can I just ask - how can I check to see if there is a leak next time without wasting coolant? I dont want to fill it up with 20 quid coolant and have it all over the floor :(

I feel like a tool for messing something this simple up

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