VW POLO 2000 6N2 1.0 ALD engine code - Polo emmisions fail

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Sat 14 Jun 2014 16:07
VW POLO 2000 6N2 1.0 ALD engine code - Polo emmisions fail - Dan the money man

Hello folks,

After any useful advice on how to resolve the issue with my wifes polo which last week failed the MOT on emmisions.

The first set of readings were:

Engine oil temp 80

Fast idle test:

Engine speed 2965 rpm FAIL

CO 0.511 FAIL

HC 115ppm PASS

Lambda 1.030 FAIL

Second fast idle test:

Engine speed 2697 PASS

CO 0.514 FAIL

HC 102ppm PASS

Lambda 1.027 PASS

Natural idle test:

Engine speed 703 rpm PASS

CO 0.493% PASS

OVERALL - FAILED

The garage say they thing the cat is on way out. I say can we try with engine hotter which they agreed to on another day. Made sure there are no exhaust leaks, un clogged all the crankcase breather pipe work and breahter box on the back of the block. Put in some redex also and changed the air filter. Took it in and the at engine oil temp 100 the results were nigh on the same.

Bit stuck as to what to do next - is it worth putting it on a fault code reader?? (would this cheap one from euros work - www.eurocarparts.com/ecp/p/tools/car-service-tools...8).

Would it not show a warning light if the cat or lambda had failed? (no warning lights currently and the car drives absolutley fine)

I dont want to fork out for a new cat if it dosent need it (but i am begining to think thats all it can be?)

Any help appreciated!

Cheers

Dan

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Sat 14 Jun 2014 21:26
VW POLO 2000 6N2 1.0 ALD engine code - Polo emmisions fail - Railroad.
Try adding Cataclean to the fuel tank and then give the car a serious thrash up the road. Failing that a new catalyst may be required. That wouldn't be that surprising on a 14 year old car. Just be aware that cheap non genuine catalysts are often inferior quality to a genuine one.
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Sun 15 Jun 2014 11:22
VW POLO 2000 6N2 1.0 ALD engine code - Polo emmisions fail - Dan the money man

Thanks for the reply. Isnt cataclean much the same kind of thing as Redex though? Might be worth a try though as its pretty cheap compared to a new catalyst.

I have since found that 1 of the 4 spark plugs was quite worn (the electrode hd worn away and the gap had gone from 1mm to 1.5 mm. Could changing that make much of a differnce?

If it does have to be a new cat - is it one or two (it seems some of them have 1 and some 2?) Im guessing the bigger engine ones have the 2 and mine should have 1?

Also what make of cat is a "good" cheap one? Ie would last at least 20k/2years?

Certainly not paying 300-400 for a genuine vw one...

Cheers

Dan

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Sun 15 Jun 2014 13:21
VW POLO 2000 6N2 1.0 ALD engine code - Polo emmisions fail - Cyd

Todays reading from the Motoring Gospels:
"Shall ye skimp on servicing to save money, then so thou shall't reap what ye sow with problems later. And it shall cost ye more".

Items like breather pipes, filters and sparks should be checked and changed or cleaned on a regular basis. Waiting until the car fails an emissions test is often far too late as the damage has been done by then.

That spark plug could be the root cause. Other problems like your blocked breathers and air filter may have been compounding it. That cylinder may be stuggling causing incomplete combustion. Your HCs are not horrendously high, so it may not be chucking too much unburnt fuel down the exhaust, nevertheless unburnt fuel can kill a cat even if it is only a little but over a long time. A misfire can also kill it.

First thing to do is make sure the engine is in a fine state of tune. Clean oil, filters, sparks, HT leads (if it has them).

With a quarter tank of fuel or less, run some cataclean and give the motor an Italian tune. If you need to put fuel in for this exercise use Shell V Power or BP Ultimate or Esso Supreme (in that order of preference).

Then take it for a retest. If this doesn't clear it then suspect the cat.

With a popular car like the Polo, you might be able to get a good secondhand cat. Get one with a reasonable warranty and have it retested just before the end of the warranty period. Or find someone who's breaking their own car.

Incomplete combustion can cause high temperatures and promote the formation of carbon deposits. See if you can get an endoscope down th eplug hole to take a look. Might even be worth doing a compression test to check for burnt valves. Especially if you can do these things yourself. If your local garage hasn't got an endoscope (no excuse, they are cheap enough) then try some local plumbers or electricians.

As you've found gunk and gunge in the breather system also suspect you've got it in oilways and th pick up gauze and laying in the bottom of the sump. Increase the frequency of oil changes and use flush too.
Frequent short journeys??

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Sun 15 Jun 2014 14:59
VW POLO 2000 6N2 1.0 ALD engine code - Polo emmisions fail - Dan the money man

Hi Cyd,

Thanks for the reply. Some valid points i canappreciate.

The plugs are supposedly good for 40k and had done 20k so didnt suspect there would be an issue. The worn plug was not worn or odd looking in any otherway apart from the electroge gap being wider and electrode slightly burn away. The old air filters were not really grubby either and were within interval. The oil and filter has been changed every 5k. The existing breather hoses were I think doing thier job but had become floppy and weak. In general i think the car is in good shape and was certainly driving well. The crankcase breather is a known issue with these small vw engines of that era, from what i read they all do it to some extent even if the engine is spot on, it will be exacerbated by short journeys though as you say. The car does 15 miles twice a day with 10 miles on the motor way so im not sure if that would be called short or not..

Looking back at the previous years emmisions test it just scrapped through on the CO at 2.9. So wonder if as you say the cat is just time expired. I think the issue with a second hand one is that these cars are normally scrapped due to engine fail as they dont really rust much (galvanised shell) so i would worry that many in breakers yards may have worn out cats too. need to find a rear ended one or somethign i guess!

I think the cataclean or more redex or whatever and mega thrash is worth a go for a re test before taking it to bits. I had to get the wife to do the italian tune up before the last test and and not sure she would have been brutal enough!

Cheers for the input though.

Dan

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Sun 15 Jun 2014 15:26
VW POLO 2000 6N2 1.0 ALD engine code - Polo emmisions fail - Railroad.
So you think the plugs are good for 40,000 miles eh? No wonder you're now having problems. This is sales pitch for new car sales. I could understand that they might go 40,000 miles if you clocked them up in six months. Spark plugs should be renewed annually, especially on low mileage cars.
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Sun 15 Jun 2014 16:00
VW POLO 2000 6N2 1.0 ALD engine code - Polo emmisions fail - Cyd

OK, so the general servicing isn't as slapdash as your OP seems to suggest. In that case there is something going on with the cylinder that's opened up that plug.

It could be a one-off faulty plug. Replace them and see if it helps. If it's not sparking correctly then this could lead to combustion problems and you may have had this issue for some time if the plugs haven't been checked.

Alternatively there could be some other problem and the faulty plug is a symptom rather than cause. The high CO and HCs suggest it's running rich. As it's only one cylinder that's burning the plug, maybe a faulty injector?? letting in too much fuel?? Improper fueling can cause plugs to foul and burn. It'd be worth getting a secondhand injector (or maybe even a set of cleaned ones) and swapping it out.
Others will be more up to date than myself on this, but I thought good modern diagnostic equipment was capable of discerning if a single cylinder is running rich or weak??? If this is the case it'd be worth paying for a session - I'm not a fan of diagnosis by guesswork, it usually leads to swapping out loads of parts that are perfectly ok.

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Fri 20 Jun 2014 00:21
VW POLO 2000 6N2 1.0 ALD engine code - Polo emmisions fail - Dan the money man

Hi again, I have since discovered that this polo engine has only the one cat (there isnt a pre catalyst in the exhaust manifold as most of the other engines) and the only lambda sensor is in the manifold (ie pre cat). Does this suggest that potentially the cat may not be to blame if the lambda reading is on the borderline of failing for reading too high as this reading is almost out of spec before the cat is even involved? How do they measure the lambda reading at the mot?? Too high means running lean i think so then the ecu would increase fueling? Is it worth taking the lambda out and trying to clean it up? I dont think there are any air leaks at the manifold but i will check this. The bolts and stud on the original downpipe/cat assembly look so rusted i am dreading trying to remove them if it has to be a new cat!Cheers, Dan

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Wed 2 Jul 2014 19:29
VW POLO 2000 6N2 1.0 ALD engine code - Polo emmisions fail - Dan the money man

Just to wrap this one up. No amount of cataclean (waste of £15 but worth a try) and servicing or getting red hot prior to test was gettting it below 0.5 CO on the fast idle.

Chucked on a cheap new bosal downpipe and cat (What I consider to be a half decent cheap option) and it was down to 0.04 CO. Job done.

Cheers

Dan

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Wed 2 Jul 2014 20:32
VW POLO 2000 6N2 1.0 ALD engine code - Polo emmisions fail - csgmart

Thank you for coming back to update us and glad you finally managed to get the car to pass.

Polos of this age are great and cheap runabouts. Have one myself. Use it for trips to the tip and general running around.

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