Cylinder 2 Misfire

sinlessUK

sinlessUK

Member
Having noticed a misfire at idle I thought I’d check which cylinder it’s coming from. So armed with VCDS I did a quick scan and nothing appeared relating to misfire just [16804 - Catalyst System; Bank 1: Efficiency Below Threshold P0420 - 35-00 - -]

So following this article >> http://www.ross-tech.com/vag-com/m_blocks/ << I went into Group 14 and noticed a misfire. Going into Group 15 I can see all misfires were occurring in Cylinder 2. Keeping the revs on I can see and hear an increase occurring.

I’ve swapped coil packs, performed the scan again and still points to Cylinder 2. I’m going to swap spark plugs next but I’ve noticed the chamber has a bit of oil in it compared to the other chambers which seem dry.

I’m assuming there shouldn’t be oil in there, and this could be causing my misfire. If cleaning and swapping the plug in this cylinder solves the misfire, how do I solve the oil in the chamber from happening?
 
My wife's old Beetle had this.

Oil on the spark plug causing a misfire. Clean the plug and it should disappear, but if oil is getting into the cylinder i think it will be a rebuild to fix it completely.


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sinlessUK said:
.................I’m assuming there shouldn’t be oil in there, and this could be causing my misfire. If cleaning and swapping the plug in this cylinder solves the misfire, how do I solve the oil in the chamber from happening?
Click to expand...

Unfortunately the most common cause for oil in the spark plug recesses is a breakdown of the silicon gasket material between the cylinder head and camshaft housing, specifically around the recess area.
It is a fair amount of work to resolve this issue, and probably best carried out when the cambelts need replacing, as the main belt has to be removed before the camshaft housing can be taken off.

I've attached a PDF showing the removal and installation process for the camshaft housing, and the specific graphic N15-0457 shows the shaded area on the underside of the camshaft housing where a bead of silicon gasket is used to mate the housing to the cylinder head.

View attachment FSI cam housing.pdf

Cheers
Jeff
 
Sorry to say, but you'll not see any change from £500, and that's without the cambelt kit and waterpump.
Obviously it's not essential to change the cambelts and waterpump if they're not due, but it is false economy to have it all apart and not do this.
OEM belt kit, waterpump and coolant is probably going to add £200 to the total.

Firstly I would clean up the spark plug recess (and clean it really well so there is zero trace of oil) and see over the course of a week if there is any oil appearing.
Take care not to use chemicals in the spark plug recess to help cleaning, because if the silicon gasket has failed the cleaning agents will seap through the failure and mix with the engine oil.

If there isn't very much oil ingress, then I'd be happy to leave the fix until a cambelt change was required.
And, in that case, I'd expect an additional £200 over the cost of the cambelt work.
Always replace the camshaft cover bolts if they have been undone.

The other possibility of area of failure is that cylinders piston oil control ring.
If oil is passing by the piston and getting up to its crown, this might produce a similar problem, but only if the spark plug gasket (the washer on the spark plug) has failed too. Under compression, any oil present in the combustion chamber would be forced past a failing spark plug gasket.
This cause of the oil is unlikely though.

Sorry for the not so great news.
Jeff
 
Hi, I had the exact same problem with the exact same allegated cause. In to garage, 3 days, many hundreds later picked up, drove away 2hrs later same miss fire. Examined no oil. Many hundreds wasted.

Many hundreds spent with Audi specialist, pipes replaced, more investigation, many hundreds spent. Drove away, as bad as it ever was. Mainly running on three cylinders.

Did a bit of thinking! instead of blindly listening to garage. What do they insulate 415000 volt transformers with? that'll be oil.

20mins in local scrapyard, popped HT lead in pocket, paid for 2x pieces of trim. Miss fire cured. Never came back.

Do the simple things first. Plugs, HT leads before the big bucks.

edited - got story in wrong order
 
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oneflewover said:
Hi, I had the exact same problem with the exact same allegated cause. In to garage, 3 days, many hundreds later picked up, drove away 2hrs later same miss fire. Examined no oil. Many hundreds wasted.

Many hundreds spent with Audi specialist, pipes replaced, more investigation, many hundreds spent. Drove away, as bad as it ever was. Mainly running on three cylinders.

Did a bit of thinking! instead of blindly listening to garage. What do they insulate 415000 volt transformers with? that'll be oil.

20mins in local scrapyard, popped HT lead in pocket, paid for 2x pieces of trim. Miss fire cured. Never came back.

Do the simple things first. Plugs, HT leads before the big bucks.

edited - got story in wrong order
Click to expand...

The FSI doesn't have HT leads --- it has individual coil packs. cheers mike
 
As you say, do the simple things first. So if the spark plug is literally sitting in an oil bath with the electrode cap and coil pack connector soaked in a 'super insulator' then it makes sense to clean everything just to make sure the full HT voltage is reaching the spark plug.

Cheers Spike
 
Not an advice, just a report, I hate misfirings: My random misfirings on not-oily #2 wanished only afer all injectors were replaced. The oily #3 never misfired, still doesn't.
 
Obviously I agree that checking and replacing the simple and cheap things first is the way to go, but the OP asked a specific question:

"If cleaning and swapping the plug in this cylinder solves the misfire, how do I solve the oil in the chamber from happening?"

And that is what prompted my replies.

Cheers
Jeff
 
Well I've cleaned the chambers and put new plugs in and still have a misfire on cylinder 2. I've got a compression tester. Any point trying it? Or straight to the garage I go.
 
Its not submerged just a little oil. The plugs where black and only been serviced in November. I'm leaning towards a faulty injector. I think I'll leave it to the garage.
 
sinlessUK said:
Its not submerged just a little oil. The plugs where black and only been serviced in November. I'm leaning towards a faulty injector. I think I'll leave it to the garage.
Click to expand...

A little oil there is not likely to cause any problems and certainly not worth spending hundreds to sort out. So just get it out (before undoing the plug ideally so that it doesn't go into the cylinder because it will contain grit and muck). Then keep an eye on it for a while.

Check the injector loom too, they can cause problems like this.

Steve B
 
So she's finally given up the ghost and in the garage. These are the thoughts of the garage. Replace injector 2 as all misfires come from cylinder 2. Replace rocker cover gasket to stop oil ingres + timing belt as it has to come off and due anyway. New set of plugs again.Price wise what should I be looking at £500 - £600
 
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I think it would be wise to replace all four injectors. They have to do the same work and spend same time replacing one or four.


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sinlessUK said:
So she's finally given up the ghost and in the garage. These are the thoughts of the garage. Replace injector 2 as all misfires come from cylinder 2. Replace rocker cover gasket to stop oil ingres + timing belt as it has to come off and due anyway. New set of plugs again.Price wise what should I be looking at £500 - £600
Click to expand...
Remember to include the cost of the pulleys and a water pump.
The injectors can be quite expensive.

I would hazard a guess of £700 hopefully less but that depends on the price of the parts they use and their labour rates too

A cambelt change alone can be upwards of £300 alone and there is a fair bit of labour to change the injectors.

I agree with Darko especially if the injector prices are sensible. Ask them how much extra for all four to be done!

Steve B
 
Birchall said:
Remember to include the cost of the pulleys and a water pump.
The injectors can be quite expensive.

I would hazard a guess of £700 hopefully less but that depends on the price of the parts they use and their labour rates too

A cambelt change alone can be upwards of £300 alone and there is a fair bit of labour to change the injectors.

I agree with Darko especially if the injector prices are sensible. Ask them how much extra for all four to be done!

Steve B
Click to expand...

I made a mistake not to have injectors replaced in 2014 when they had engine pulled up for timing belt and water pump replacements, they had access to injectors and everything else hidden behind.



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Birchall said:
Remember to include the cost of the pulleys and a water pump.
The injectors can be quite expensive.

I would hazard a guess of £700 hopefully less but that depends on the price of the parts they use and their labour rates too

A cambelt change alone can be upwards of £300 alone and there is a fair bit of labour to change the injectors.

I agree with Darko especially if the injector prices are sensible. Ask them how much extra for all four to be done!

Steve B
Click to expand...

So £700ish for what I need plus extra for the pulleys and water pump etc? Unfortunately I can't afford all injectors to be replaced otherwise I would.
 
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