Idle problems 51 plate Leon

[WarChild007]

If left idling for a couple of mins (on the drive to warm up/ de mist or in heavy traffic) my gf's 51 plate 1.6 Leon starts to fire on 3 cylinders. The engine fault light on the dash flashes then after about 10 mins goes constant . When the light turns constant the problem stops and it runs ok, after a day the light goes out and its seems ok. We've changed the EGR valve, plugs, ignition leads and transformer/coil pack but still has this issue. Any ideas?

[Crasher]

What is the engine code, how many miles and is the car run on 95RON normal unleaded fuel?

[WarChild007]

What is the engine code, how many miles and is the car run on 95RON normal unleaded fuel?

Cars done just over 48k miles, yeh mainly on Shell unleaded but occasionally on V-Power.
Engine code is AUS

What you thinking?

[Crasher]

I thought you were going to say AUS. I have had a number of AUS engines burn out exhaust valves due to prolonged use of normal 95RON unleaded fuel. In VW’s own words “98 unleaded (in exceptional circumstances min. 95 RON, however with reduced performance)” but I have also found this valve burning issue on other 1.4 and 1.6 16v engines designed to be run primarily on 98RON fuel. For your and others information, you can find the fuel rating printed on a sticker inside the petrol flap.

Firstly a fault code read will identify the cylinder in question (for some odd reason, usually cylinder 2) and then a compression test will confirm the problem but as these engines are very sensitive to a loss of compression, the gauge needs to be quite accurate. The reason the misfire is so bad is that the engines ECU is programmed to EU4 emissions standards so if the ECU detects a slight misfire (using crank speed and lambda sensor signals) it cuts out the injector to the poor performing cylinder to reduce emissions and the possibility of catalytic converter damage.

The way we deal with the problem is to install a genuine VAG exchange cylinder head which at first glance appears to be expensive (£625 inc. VAT) compared to a rebuild of the original but when you consider it comes fully assembled with valves and the lifters and roller rocker fingers included, it is actually extremely good value and it carries a two year labour inclusive warranty, no matter who installs the head.

[WarChild007]

I thought you were going to say AUS. I have had a number of AUS engines burn out exhaust valves due to prolonged use of normal 95RON unleaded fuel. In VW’s own words “98 unleaded (in exceptional circumstances min. 95 RON, however with reduced performance)” but I have also found this valve burning issue on other 1.4 and 1.6 16v engines designed to be run primarily on 98RON fuel. For your and others information, you can find the fuel rating printed on a sticker inside the petrol flap.

Firstly a fault code read will identify the cylinder in question (for some odd reason, usually cylinder 2) and then a compression test will confirm the problem but as these engines are very sensitive to a loss of compression, the gauge needs to be quite accurate. The reason the misfire is so bad is that the engines ECU is programmed to EU4 emissions standards so if the ECU detects a slight misfire (using crank speed and lambda sensor signals) it cuts out the injector to the poor performing cylinder to reduce emissions and the possibility of catalytic converter damage.

The way we deal with the problem is to install a genuine VAG exchange cylinder head which at first glance appears to be expensive (£625 inc. VAT) compared to a rebuild of the original but when you consider it comes fully assembled with valves and the lifters and roller rocker fingers included, it is actually extremely good value and it carries a two year labour inclusive warranty, no matter who installs the head.

That sounds exactly like it. I was saying yesterday to my GF it seems that the ECU is having an affect as if you switch the engine off for about 30secs the problem stops.

We've had VAG com on it (its a misfire on cylinder 3) and its been compression tested, compression was slightly lower than it should have been.

Has the cylinderhead you provide been adapted by yourselves or is it like that straight from VAG?

Sorry I didnt thank you for your response! Thanks :biggthump

[Crasher]

We don’t provide it, we buy it from our local VAG Trade Parts Specialists (TPS) and if you were to buy one, you would go to your local VW dealer or your garage would use their own TPS. If it was fitted by someone other than VW, after fitting you/the garage take it to the supplying dealer (or the one appointed by the TPS) who inspects it (they sometimes make a small charge for this) and then they issue you with a Green Card and that entitles you to a warranty repair of the new parts for the next two years at ANY VW UK dealer.

[WarChild007]

We don’t provide it, we buy it from our local VAG Trade Parts Specialists (TPS) and if you were to buy one, you would go to your local VW dealer or your garage would use their own TPS. If it was fitted by someone other than VW, after fitting you/the garage take it to the supplying dealer (or the one appointed by the TPS) who inspects it (they sometimes make a small charge for this) and then they issue you with a Green Card and that entitles you to a warranty repair of the new parts for the next two years at ANY VW UK dealer.

Would you have a part number and I'll enquire with my local garage?
Would using higher ron fuel now reduce the occurance of it happening?

Many thanks for your help and suggestion.

[Crasher]

I get the part number to be 036 103 264 CX at £624.08 inc. VAT but check before ordering.

There is no point changing to V Power or Tesco 99 now (both actually 99RON), it is too late if the compressions have dropped

[WarChild007]

I get the part number to be 036 103 264 CX at £624.08 inc. VAT but check before ordering.

There is no point changing to V Power or Tesco 99 now (both actually 99RON), it is too late if the compressions have dropped

Thank you, looking at the petrol flap again its 98ron/95 rnz :banghead: should have looked more closely at it.

At the moment it only happens when the car is left to idle. What would happen if we didnt do anything and just carried on with it? Would it cause damage to other things or would the prob just get worse.

[Crasher]

It will just get to the point that it will only run on there cylinders all the time and it won't do the cat or lambda sensors any good so in the end you will have to do the head and those so adding another £600 odd (at genuine prices) to the job.

[WarChild007]

It will just get to the point that it will only run on there cylinders all the time and it won't do the cat or lambda sensors any good so in the end you will have to do the head and those so adding another £600 odd (at genuine prices) to the job.


Damn it, there goes the manifold for my RS!:(

[WarChild007]

Thought I'd give an update.
I got a Vege cylinder head in the end and save a few quid, had an issue with the blanking bolt in the oil sensor hole though so had a new one sent out.

After getting this fitted and the cambelt, water pump changed they realised the flexi pipe was blowing badly. Then we realise that the flexi and cat are all in one and not seperate pipes, meaning that we now need to buy a flexi pipe and a new cat.:banghead::cussing:

[rickrobbo]

I have a similar problem. My 1.8t misfires when first started. When engine is warm and revs settle then it is mostly fine. It just occasionally misses at around 2000 revs. Done loads to try and get rid of problem -new cat, landa sensors, coolent switch etc but struggling to solve it. can anyone help?

[WarChild007]

I have a similar problem. My 1.8t misfires when first started. When engine is warm and revs settle then it is mostly fine. It just occasionally misses at around 2000 revs. Done loads to try and get rid of problem -new cat, landa sensors, coolent switch etc but struggling to solve it. can anyone help?

Does it actually run on 3 cylinders or is it just a slight misfire?

Mine misfired when high revs in second and third, put in some Shell V Power and some Redex took it on a long motorway trip and it cleared it out. I was doing lots of short journeys at the time though, think it just needed a good run.

[rickrobbo]

slight misfire, I've tried the v power, it does run better but still misfires occasionally, especially in 2nd gear at about 1800 revs.

[Crasher]

That sounds like a coil pack on the way out. Up until recently, the only failed coil packs I saw just died and that was it but the latest batch seem to fail slowly, rather than suddenly. Note down the part number and dates on the coil packs and post them on here.