# MOT failure



## Mindis (Feb 2, 2011)

Hello guys,
This morning took my car for MOT retest and it have failed on emissions again.
Could you guys point me where to start looking. It has a slight misfire as well. Recently it had new air flow meter, O2 sensor, camshaft position sensor, new spark plugs, new ignition coil. What else ? New catalytic converter? And the car is VW golf mk4 1.6 8v.
Thanks for any ideas.


----------



## Steve (Mar 18, 2014)

Motoring section will be a good start...

To be honest without looking at readings from the emission report and looking at the cars onboard readings who knows...


Needs to be looked at properly mate


----------



## steveo3002 (Jan 30, 2006)

get it on a diagnostic machine and see what it says

chances are its the misfire causing the emmsions prob


----------



## RD55 DUN (Dec 30, 2008)

As above, likely to be the misfire causing the emissions to be high. A new Cat would be rather expensive also.

Or find a “friendly” MOT tester.


----------



## Mindis (Feb 2, 2011)

Well, I did diagnostics with VCDS yesterday and it didn't come up with any faults?

Fast Idle 
CO limit 0.300 - actual 4.588
HC limit 200 - actual 632
Lambda min limit 0.970 - actual 0.868

Natural idle 
Co limit 0.500 - actual 3.166


----------



## percymon (Jun 27, 2007)

You need the fault codes from the on board diagnostics - good news is you've replaced half the items already !

Could be anything from a faulty connector, faulty spark plug, or even dirty injectors. You could try a bottle of Cataclean if the OBD scan is clear but it does sound to be more than just needing a system clean.


----------



## steveo3002 (Jan 30, 2006)

fix the mis fire first ..clearly isnt right with a misfire

once you think its right consider a fresh oil change incase its got some fuel in it and fresh air cleaner , good hard run with lots of revs before taking it straight to the mot place


----------



## Gaffa22 (Aug 24, 2014)

And don't use supermarket petrol


----------



## Mindis (Feb 2, 2011)

Just scanned again and it's coming up with 2 fault codes now:
00525 - Oxygen (Lambda) Sensor (G39)
00537 - Lambda (Oxygen Sensor) Regulation

Dodgy O2 sensor?


----------



## steveo3002 (Jan 30, 2006)

asked my mate he says-

could be o2, or maybe coolant temp sensor. what he needs to do is plug it to proper tool and read the measuring blocks so he can see all sensor inputs in real time, otherwise you're just guessing

worth cleanign the throttle body out, the reset it in vagcom

if u unplug the lambda and it runs better chances are its sensor


----------



## AllenF (Aug 20, 2012)

Try looking at the EGR valve first. The lambda is after it in the system so if EGR is dirty/ US then changing the lambda is going to result in the same.


----------



## Mindis (Feb 2, 2011)

steveo3002 said:


> asked my mate he says-
> 
> could be o2, or maybe coolant temp sensor. what he needs to do is plug it to proper tool and read the measuring blocks so he can see all sensor inputs in real time, otherwise you're just guessing
> 
> ...


Thanks,
I have cleaned and readapted throttle body just yesterday.
I have unpluged lambda sensor and it's running no different (feels better but it might be only placebo) ???

I have replaced coolant temperature sensor recently but had/have no issues with temperature gauge, it's showing temperature as normally would ???


----------



## Mindis (Feb 2, 2011)

AllenF said:


> Try looking at the EGR valve first. The lambda is after it in the system so if EGR is dirty/ US then changing the lambda is going to result in the same.


Correct me if I am wrong, but I don't think it has EGR valve


----------



## steveo3002 (Jan 30, 2006)

the temp sender is 2 inside 1 unit , ebay type ones are often poop


----------



## AllenF (Aug 20, 2012)

Its a common engine same in the audis and seats.
If the engine code is AKL then no it wont have one if not then yes it will have.
The most common problem on these engines is the throttle body which WILL need setting up on puter when you remove/clean/ replace.
Check all the hoses as well cos if one of the vaccum ones are split or US then you could get same issues


----------



## w138pbo (Jul 10, 2013)

its the missfire thats causing it to fail. And brining up the lambda fault.

Need to look at whats causing the missfire.
spark plugs and lead/coils would be first thing to check.


----------



## Steve (Mar 18, 2014)

Mindis,

Please don't take any offence..


Your going to gain nothing but unplugging things and guessing.

Take it to someone with the knowledge and the suitable equipment to diagnose the car's fault.

Someone with a code reader and the internet isnt going to get it sorted...


:thumb:


----------



## Mindis (Feb 2, 2011)

AllenF said:


> Its a common engine same in the audis and seats.
> If the engine code is AKL then no it wont have one if not then yes it will have.
> The most common problem on these engines is the throttle body which WILL need setting up on puter when you remove/clean/ replace.
> Check all the hoses as well cos if one of the vaccum ones are split or US then you could get same issues


It is AKL engine. 
I have removed, cleaned and sett up throttle body with VCDS, car is running much better ( with proper way of setting it up ) when it was before. 
I will check hoses again for the air leaks but I have replaced air intake hose with the new one.


----------



## Mindis (Feb 2, 2011)

Steve said:


> Mindis,
> 
> Please don't take any offence..
> 
> ...


I would do that, but I don't think that car is worth that much. Even the ''basic'' garages charge around £40 per hour, and by the time they finish I could replace most parts on that car for the same price.


----------



## m4rkymark (Aug 17, 2014)

00537 could mean its the MAF that's gone.


----------



## possul (Nov 14, 2008)

Why dont you change the glove box lid, youve changed everything else

Joking aside, just reading codes wont help that much. 4 or two pin lambda? Internal heating elements gone down? Signal and earth wires good? All things that need be checked correctly in orfer to correctly diagnose a fault.
Crank case breather pipes split? Small vac lines split or perished?
Any loose or corrded earths?
Coolant temp sensor? (should have two, one for gauge other for engine management) sends wrong signals to ecu and mucks up fuelling and spark etc etc
Clear codes and go for a drive and make sure there the only codes that come back on and go from there.
Genuine parts fitted? - I suspect not
As you have found simply replacing parts isnt doing a thing


----------



## Steve (Mar 18, 2014)

Mindis said:


> I would do that, but I don't think that car is worth that much. Even the ''basic'' garages charge around £40 per hour, and by the time they finish I could replace most parts on that car for the same price.


Yes and spend more mending it than you may need to ?

Seriously just wasting time and money


----------



## Steve (Mar 18, 2014)

possul said:


> Why dont you change the glove box lid, youve changed everything else
> 
> Joking aside, just reading codes wont help that much. 4 or two pin lambda? Internal heating elements gone down? Signal and earth wires good? All things that need be checked correctly in orfer to correctly diagnose a fault.
> Crank case breather pipes split? Small vac lines split or perished?
> ...


:thumb:


----------



## Mindis (Feb 2, 2011)

possul said:


> Why dont you change the glove box lid, youve changed everything else
> 
> Joking aside, just reading codes wont help that much. 4 or two pin lambda? Internal heating elements gone down? Signal and earth wires good? All things that need be checked correctly in orfer to correctly diagnose a fault.
> Crank case breather pipes split? Small vac lines split or perished?
> ...


I haven't replaced all this parts in one night, it was within the last 6 months.
It is 4 pin lambda. I believe that it might be dodgy lambda sensor to start with, as it was universal sensor. 
I do understand what are you saying guys, but I don't think it's worth taking this car to any garage, it will be £80 ( this is what usually every garage is charging for reading codes around here) plus repair.


----------



## steveo3002 (Jan 30, 2006)

if you get yourself on a vw forum chances are someone will the have code reading gear , ive seen many folk get thiers read for nothing or a drink , i dont think its too pricey to get hold of anyway 

the shocking quality of pattern parts doesnt help these days , its worth buying genuine or at least a know good brand


----------



## Steve (Mar 18, 2014)

Scrap the ****ing car then ?


----------



## possul (Nov 14, 2008)

But you have still replaced them all thats the thing.
Back to basics, timing, sticking valves - rare but can happen. Slight misfire or is it hesitation? Check the tekp sensor connector doesnt have water in it.
Things like coil packs and 02 sensors etc etc, id stick genuine on depending on the manafactuer, vw yes because they seem to have finer tolerences for things like this.
By universal do you mean one you solder in your self? Did you actually check connector?


----------



## Sh1ner (May 19, 2012)

Have you read the live data from the data/measuring blocks.
It is a simple system and that will show you if what the ecu is seeing from the sensors and also show any switching components, front and rear Lambda sensors etc and what they are actually doing. Lambda sensors should constantly switch between about 100ma and 900ma once the sensors are warm and up to temperature. You will be able to see the coolant temp as it rises in real time etc
If you have a misfire that will be the first thing to isolate.
Is the misfire always there? High speed and low/idle.
Is there an air leak at the inlet manifold to head gaskets/o'rings?
Have the leads been checked. If not they should be examined very closely from cap end to cap end look for a slight round burn mark where it might be arcing through. I know they are a bit of a pain to get to but you need to isolate the problem to either the mechanical, fuel, ignition, or electrical system but you will only do it if you work systematically and eliminate each system one by one. The ignition(sparks)system would be first on my list then fuel system then mechanical (valves) then the electrical system.
Can you remove each plug lead whilst it is running to see if only one cylinder has a problem or it is a general misfire caused by say low fuelling due to something like a temp sensor.
Can you check the injectors are being powered have secure connectors and no corrosion. Do they all squirt fuel.
If the misfire is confined to one cylinder you might need a compression/cylinder leakage test to see if you have an exhaust valve/seat that is leaking.
Have you checked all the wires in the engine loom for any chafing, breaks, corroded earths etc
Is the engine wiring loom muti plug clean and dry. Does the ecu have a good earth and is there any internal corrosion. They used to suffer because they got wet and corroded terminals or the pcb. Sometimes you could resolder other times it caused component faults that were not easily fixable but it is just as easy to replace it with second hand.
It is sometimes not as easy as just changing out parts and a bit of time narrowing it down makes an educated guess much easier. These engines are not the most accessible but as others have said there really are no shortcuts.


----------



## Mindis (Feb 2, 2011)

steveo3002 said:


> if you get yourself on a vw forum chances are someone will the have code reading gear , ive seen many folk get thiers read for nothing or a drink , i dont think its too pricey to get hold of anyway
> 
> the shocking quality of pattern parts doesnt help these days , its worth buying genuine or at least a know good brand


My friend has genuine vag-com scanner, that shows all the values ect... but as much as we could work out ( by far not an experts) it didn't have any fault codes yesterday evening after we reset ECU and after a short run. But today when I got back from MOT station, there was two faults stored in ECU.


----------



## Mindis (Feb 2, 2011)

Steve said:


> Scrap the ****ing car then ?


This is what I am thinking about ...


----------



## Mindis (Feb 2, 2011)

possul said:


> But you have still replaced them all thats the thing.
> Back to basics, timing, sticking valves - rare but can happen. Slight misfire or is it hesitation? Check the tekp sensor connector doesnt have water in it.
> Things like coil packs and 02 sensors etc etc, id stick genuine on depending on the manafactuer, vw yes because they seem to have finer tolerences for things like this.
> By universal do you mean one you solder in your self? Did you actually check connector?


Yes, the one that you have to solder your self.


----------



## Mindis (Feb 2, 2011)

Sh1ner said:


> Have you read the live data from the data/measuring blocks.
> It is a simple system and that will show you if what the ecu is seeing from the sensors and also show any switching components, front and rear Lambda sensors etc and what they are actually doing. Lambda sensors should constantly switch between about 100ma and 900ma once the sensors are warm and up to temperature. You will be able to see the coolant temp as it rises in real time etc
> If you have a misfire that will be the first thing to isolate.
> Is the misfire always there? High speed and low/idle.
> ...


Thank you very much. Plugs is new, new ignition coil, and as much as I could tell, all spark plugs were fine, but I will double check. 
I have removed and checked ECU, connector seems to be fine and ECU itself inside seems to be OK. No broken solder or any burned marks or smells. 
Thanks for all the pointer, will start from the begining.


----------



## kings.. (Aug 28, 2007)

put a new o2 sensor on, put a new temp sensor in, and clean the maf if you haven't already then put some fuel treatment through it and give it a good blast.

its not going to be anything too serious..


----------



## Mindis (Feb 2, 2011)

Quick question guys, 
in the picture that small hose highlighted in red, which way air should be moving? towards the throttle body or other way?


----------



## kings.. (Aug 28, 2007)

That hose will be under vacuum. the air will be pulled through it to the throttle body.. where does that hose go to?? rocker cover?


----------



## Andy-P (Jun 1, 2014)

Apologies if someone else has mentioned it, but have you given any thought to replacing the HT leads?? You need to eliminate the misfire first.


----------



## Toxicvrs (May 21, 2014)

Vacuum pipe so should be sucking air


----------



## possul (Nov 14, 2008)

Andy-P said:


> Apologies if someone else has mentioned it, but have you given any thought to replacing the HT leads?? You need to eliminate the misfire first.


If they have a metal shiled around the plug end then this usd to cause the spark to jump. Can physically see it sometimes.
Good shout


----------



## Andy-P (Jun 1, 2014)

possul said:


> If they have a metal shiled around the plug end then this usd to cause the spark to jump. Can physically see it sometimes.
> Good shout


On that engine they can also go green inside the lead where they attach to the coil, which is representative or water penetration and corrosion.


----------



## Mindis (Feb 2, 2011)

kings.. said:


> That hose will be under vacuum. the air will be pulled through it to the throttle body.. where does that hose go to?? rocker cover?


Looks like it's going into inlet manifold, and it's sucking air quite heavily, I can even hear it. But my thought is why would some measured air bypass throttle body?


----------



## Mindis (Feb 2, 2011)

New spark plugs and leads, still the same  could engine misfire due to worn out piston rings and fail mot on emissions ? It's not using oil and it's not smoking but I don't have any other explanation.


----------



## Steve (Mar 18, 2014)

So youv'e spent more money and no closer..

Maybe having a diagnostic done was cheaper in the beginning rather than just bolting stuff on.

Have ago hero auto repairs :thumb:


----------



## Sh1ner (May 19, 2012)

I am puzzled as to why you have spent yet more money and changed the plugs and leads without first carrying out some tests to establish in what area the misfire lies?
With respect, I cannot imagine it would take me more than 1/2 hour to isolate the problem.
You would honestly be better off taking it to someone who knows what they are doing.
With some competent basic testing you may not even require any diagnostics.


----------



## steveo3002 (Jan 30, 2006)

it could be anything to blame as the others have said get someone that knows what theyre doing to scan it and tell you whats wrong


----------



## Hasan1 (Jul 1, 2011)

You could just get a obd2 tool for £20 and find the problem out without spending too much more money


----------



## Mindis (Feb 2, 2011)

Hasan1 said:


> You could just get a obd2 tool for £20 and find the problem out without spending too much more money


I have scanned with the proper VAG-COM scanner but it's not showing anything at all.

The problem is that couple people already had a look at it, and they are saying is that they want so much per hour and it will take as long as it will take.


----------



## dubber (Oct 2, 2011)

Mindis said:


> I have scanned with the proper VAG-COM scanner but it's not showing anything at all.
> 
> The problem is that couple people already had a look at it, and they are saying is that they want so much per hour and it will take as long as it will take.


Where are you located mate?


----------



## Mindis (Feb 2, 2011)

Sh1ner said:


> I am puzzled as to why you have spent yet more money and changed the plugs and leads without first carrying out some tests to establish in what area the misfire lies?
> With respect, I cannot imagine it would take me more than 1/2 hour to isolate the problem.
> You would honestly be better off taking it to someone who knows what they are doing.
> With some competent basic testing you may not even require any diagnostics.


They were quite cheap to replace, so why not. 
It is quite hard to find a good garage around here, and they charge quite large amount of money just to plug in diagnostics, one garage wanted £80 just to plug it in and scan.
I have lost hope with the garages around here, i just don't trust them any more. in one garage I had to tell them how to change shock absorbers, other garage ''experts'' couldn't find why air conditioning wasn't working, so I had to do it myself and done in 2 minutes with the help of internet. Third garage do jobs that they like as other is ''to time consuming''. 
i live in quite small village so I am not spoiled for choise.


----------



## Mindis (Feb 2, 2011)

dubber said:


> Where are you located mate?


Spalding, Lincolnshire.


----------



## dubber (Oct 2, 2011)

Mindis said:


> Spalding, Lincolnshire.


Anh to far for me or I would have had a look for you. Feel free to pm me with questions.


----------



## Mindis (Feb 2, 2011)

dubber said:


> Anh to far for me or I would have had a look for you. Feel free to pm me with questions.


Thanks :thumb:

Any ideas how to check/test throttle body?


----------



## dubber (Oct 2, 2011)

Vag com mate,


----------



## Mindis (Feb 2, 2011)

dubber said:


> Vag com mate,


Can you check it's ''health'' vith vag-vom? Or just adjust it? 
"Adaptation 10, read, save, yes" then go into "Basic Settings 04, Group 098, Go", wait 20 seconds, exit and then turn off the ignition for 20 seconds. - this is how we adapted throttle body.


----------



## dubber (Oct 2, 2011)

Thats correct, you did it correctly. You can't check its health as such.


----------



## Alzak (Aug 31, 2010)

I bet faulty/cheap lambda sensor is the problem, i have had exactly same problem with cheap lambda sensor used in my GF Fiat Punto from euro car parts after failing MOT i went and bought bosch part on same day retest passed with flying colours.


----------



## Mindis (Feb 2, 2011)

Is there any way of testing Lambda sensor?


----------



## Dannbodge (Sep 26, 2010)

I would change the lambda and a couple of tanks of decent fuel and an Italian tune up.

My BMW failed on CO emissions which was down to lambdas. New lambdas didn't fix the problem straight away but after a long motorway blast in 4th gear and a few redlines it was fine and better then the previous year.


----------



## possul (Nov 14, 2008)

YouTube it. There is plenty of vids on there.
You need to know the correct pins and what the voltage should be, I dont have access to wiring diagrams
Should have a 12volt feed and earth for the heater circuit, a signal wire from the ecu and an earth.
The signal voltage will vary as this determines what adjustments to make on fuel trim.
What colour were the plugs when you removed them? Will help to work if it is actually running ****. If one iant right then it would point towards a particular cylinder.
Swap plugs and see if its stays on the same cylinder.
Could injector be partially blocked, incorrect spray pattern. Someone on here was doing ultrasonic injector cleaning. Is that worth a shot


----------



## Trip tdi (Sep 3, 2008)

By yourself failing emissions have you been informed by how much out by ?


----------



## Mindis (Feb 2, 2011)

Trip tdi said:


> By yourself failing emissions have you been informed by how much out by ?


first time:

Fast Idle 
CO limit 0.300 - actual 4.588
HC limit 200 - actual 632
Lambda min limit 0.970 - actual 0.868

Natural idle 
Co limit 0.500 - actual 3.166

second time it was better, but he didn't record it as I wouldn't have to pay next time when I come down.


----------



## possul (Nov 14, 2008)

Have you actually had the cat off and checked. With Co that high thats were id be looking. A garage will be able to checked wether you lambda sensors are working, will give an indication as to wether the cat is actually doing its job


----------



## Mindis (Feb 2, 2011)

possul said:


> Have you actually had the cat off and checked. With Co that high thats were id be looking. A garage will be able to checked wether you lambda sensors are working, will give an indication as to wether the cat is actually doing its job


No, I haven't checked cat.
Would worn out cat cause over fueling ?


----------



## possul (Nov 14, 2008)

It would. The ecu needs before and after readings for it to put correct fuel mixture into the cylinders.
Will have an effect for sure


----------



## Mindis (Feb 2, 2011)

possul said:


> It would. The ecu needs before and after readings for it to put correct fuel mixture into the cylinders.
> Will have an effect for sure


Please correct if I am wrong, but I believe that this engine has only one lambda sensor? As in the plastic box where it is connected, it's only one plug coming from the car


----------



## Mindis (Feb 2, 2011)




----------



## Trip tdi (Sep 3, 2008)

I have a feeling it might be the lambda sensor that is the cause should only be one, ring VW tomorrow and they will inform you.
I know what I would do stick a wynns emissions reducer can be brought from halfords, should reduce the emissions but the fault will remain just to get the car passed and sail through. the readings are high dude.


----------



## possul (Nov 14, 2008)

Ive not worked on vws for getting close to two years.
Most have a pre and post cat o2 sensor. Ring vw parts up and ask them, they will know for for sure.
Im afraid my Internet diagnosing is done though without looking at the car. If I think.of anything il post it
They had problems with accelerator pedal position sesnor, but doubt its related


----------



## Mindis (Feb 2, 2011)

Had to take car for a retest today, and it passed on the natural idle but failed on the fast idle. It's much better to where it was, but still a bit off. 

CO was 4.588 now 0.730
HC was 632 now 212

Could it still be a little of because of the minor leak in the exhaust?


----------



## Alzak (Aug 31, 2010)

Mindis said:


> Had to take car for a retest today, and it passed on the natural idle but failed on the fast idle. It's much better to where it was, but still a bit off.
> 
> CO was 4.588 now 0.730
> HC was 632 now 212
> ...


Did you took your car for motorway blast before emission test ? High tempworks well on cleaning cat.


----------



## m500dpp (Feb 17, 2006)

My MX5 was always marginal and I was advised it could be an exhaust leak but I couldnt find one. I had an aftermarket big bore exhaust and I think the freeflow of this did not allow the cat to fully warm up. Stuffing a rag up the exhaust helped but of course you cannot do that at an MOT


----------



## Mindis (Feb 2, 2011)

Alzak said:


> Did you took your car for motorway blast before emission test ? High tempworks well on cleaning cat.


No, I din't  there is no motorway near me, and didn't want to drive around without mot or road tax, I think that would helped a lot.


----------



## Mindis (Feb 2, 2011)

m500dpp said:


> My MX5 was always marginal and I was advised it could be an exhaust leak but I couldnt find one. I had an aftermarket big bore exhaust and I think the freeflow of this did not allow the cat to fully warm up. Stuffing a rag up the exhaust helped but of course you cannot do that at an MOT


Unfortunately I had to wait for about 30 minutes after arriving at MOT station until they took my car for retest, I don't think that helped.


----------



## Sh1ner (May 19, 2012)

Mindis said:


> Had to take car for a retest today, and it passed on the natural idle but failed on the fast idle. It's much better to where it was, but still a bit off.
> 
> CO was 4.588 now 0.730
> HC was 632 now 212
> ...


No, A minor leak will give a high Lambda reading as it will be letting in extra oxygen which will show as high Lambda. If the HCs are high, you have unburned fuel.


----------



## Mindis (Feb 2, 2011)

Sh1ner said:


> No, A minor leak will give a high Lambda reading as it will be letting in extra oxygen which will show as high Lambda. If the HCs are high, you have unburned fuel.


Lambda reading is slightly higher then the maximum is allowed but that hole is after lambda sensor, would it make any difference ?


----------



## Andy-P (Jun 1, 2014)

Mindis said:


> Lambda reading is slightly higher then the maximum is allowed but that hole is after lambda sensor, would it make any difference ?


From my experience (as a former MOT tester long time ago), it is possible. You need to seal it up.

Is the misfire still present? A misfire is very bad for a catalyst - unburnt fuel will irreparably damage it. Some engine's will shut down the injector when it recognises a misfire of a specific cylinder, but I'm not sure about yours.


----------



## Sh1ner (May 19, 2012)

Mindis said:


> Lambda reading is slightly higher then the maximum is allowed but that hole is after lambda sensor, would it make any difference ?


Yes. A hole before or after the lambda sensor will make a difference to the lambda reading as the probe is reading the level in the exhaust from the back of the car not just where it counts at the lambda sensor. The rearmost if you have two.
I have MOTd thousands of vehicles and a major/minor leak is usually the cause of high lambda.
High CO on the otherhand can have many causes.
Stuffing a rag up the exhaust slows/stops the flow of fresh oxygen being sucked into the exhaust so the lambda level falls if it is a minor leak.


----------



## Mindis (Feb 2, 2011)

Andy-P said:


> From my experience (as a former MOT tester long time ago), it is possible. You need to seal it up.
> 
> Is the misfire still present? A misfire is very bad for a catalyst - unburnt fuel will irreparably damage it. Some engine's will shut down the injector when it recognises a misfire of a specific cylinder, but I'm not sure about yours.


Misfire is still present, constant but it's very irregular ( I wouldn't say it's one cylinder, and it is minor. MOT tester didn't mention anything about it). I think that lambda high readings and misfire is related, by that I mean that lambda readings is high due to that hole therefore it is running rich


----------



## Andy-P (Jun 1, 2014)

Can you remove the oil filler cap when the engine is running? (Strange question I know.)


----------



## Mindis (Feb 2, 2011)

I believe I did. Will try in a sec.


----------



## Mindis (Feb 2, 2011)

Yes, it running fine when cap is removed.


----------



## Andy-P (Jun 1, 2014)

Is it difficult to remove though - Is it being sucked on strongly?


----------



## Mindis (Feb 2, 2011)

no, I would say same as with engine off


----------



## Steve (Mar 18, 2014)

Have ago hero diagnostics :thumb:


----------



## Andy-P (Jun 1, 2014)

Ok. The 1.8T and 2.0T petrol VW/Audi engines can suffer from defective crankcase breathers which cause lumpy idling with EML on, sometimes with misfire recognition faults stored in the fault memory, and near impossible to remove the oil filler cap with the engine running due to the suction from the air intake going through the defective valve into the engine. 

Was just a thought.


----------

