MOT failure

[jeremiah]

I have a 2004 Fabia 1.2 6v that has failed an MOT retest on emissions:

Fast Idle:

CO max=0.3 actual=2.8

HC max=200ppm actual=91

Lambda expected 0.97-1.03 actual=0.919

Second Fast Idle:

CO max=0.3 actual=3.1

HC max=200ppm actual=61

Lambda expected 0.97-1.03 actual=0.910

Natural Idle

max=0.5% actual=0.575

After the first failure a Skoda dealer advised me to replace the second (i.e. after the cat) lambda probe. He wanted £450 to replace the probe and the back half of the exhaust, so I had it instead done for £230 at a family-run garage. [i have been willing to put up with their prices for years, but this time they MOTed a car they knew would fail and then told me I no longer had an MOT as a result (factually incorrect). They also said the retest would be free provided they did the work (true, but it was free anyway). So I thought that if I was ever going to try using an independent garage, this had to be the time. ]

The (yet another) garage that did the MOT said it was probably the cat, but they were not certain. They are willing to replace it for £430. I think I can probably get it done for under £300 (http://cats2u.co.uk/index.php?cPath=2686_2688 want about £200 for the cat, which leaves enough for fitting and VAT).

What I wondered was: should I take the car back to Skoda and let them diagnose whatever the current problem is? I have no idea how much they will want to do it, but let me assume it is £100. There is some chance of them saying "change the cat", so *if* the probability of the cause being the cat is less than about 2 in 3, I am on average better off spending £100 to find out what the real cause is. Otherwise I am better off just changing the cat anyway, and retesting the car. (This assumes that whenever they say it is the cat, it really is.)

Many thanks for any help, suggestions, etc.

[mudyf0x]

hi and welcome to Briskoda

Apart from poor emissions are you experiencing and other probs with the car? how many miles on your clock and how often is it serviced?

have you changed oil lately? plugs and filters?...

[jeremiah]

Apart from poor emissions are you experiencing and other probs with the car? how many miles on your clock and how often is it serviced?

have you changed oil lately? plugs and filters?...

Many thanks for the quick reply. The car has done a bit over 52000 miles. It has been serviced at a dealer every year, and had an annual service on the same day as the first MOT failure. They certainly changed the oil but probably not the plugs. I forgot to mention the engine management unit light was intermittently on for the last six months or so (but is off now). The reason was that the second lambda probe was "erratic". I was told I could continue to drive the car as long as the light went out after a few days, so I did. The codes were reset today, so it is too early to say if anything else will be logged.

Edited 19 May, 2010 by jeremiah

[shark_90]

I would suggest a good quality fuel treatment such as Forte Advanced Gas Treatment

[allytech]

Catalyst failures are quite common on the 1.2, £300 to replace is massively excessive.

Skoda advise NEVER using fuel additives in the owners manual and also on most engine courses techs are told in no uncertain terms not to use any additives.

[mudyf0x]

my fab is a 2003 and is a 1.2 6v (49k), i recently did a oil, plugs and filter change and was shocked to see the state of the plugs, they where well burnt and dont think they had ever been changed...

car had poor economy before service... was getting about 140miles per 20liters of fuel now im getting 170, which i think is quite a result.., starting to go of topic here but u can see where im coming from...

do your plugs or at least check the and the gap, if they are ngk plugs i think the gap should be 1mm , also when getting the car serviced did they use the correct oil? cheep crappy oil can have detrimental effects on your emmisions .

[jeremiah]

£300 to replace is massively excessive.

Good! Could you please suggest where to get the part for substantially less? It might be the South-East factor, but Skoda wanted £225 to replace the lambda probe and another £225 to replace the back part of the exhaust. It turns out there is a profit margin left at half the price :-( I expect their quote for the cat would be a lot higher than either of the other two ....

[jeremiah]

my fab is a 2003 and is a 1.2 6v (49k), i recently did a oil, plugs and filter change and was shocked to see the state of the plugs, they where well burnt and dont think they had ever been changed...

car had poor economy before service... was getting about 140miles per 20liters of fuel now im getting 170, which i think is quite a result.., starting to go of topic here but u can see where im coming from...

I get 150 but floor it whenever the power is useful. It accelerates as happily as ever. I think the CO is out by an absolutely huge margin, so there is probably a correspondingly substantial cause.

do your plugs or at least check the and the gap, if they are ngk plugs i think the gap should be 1mm , also when getting the car serviced did they use the correct oil? cheep crappy oil can have detrimental effects on your emmisions .

I imagine the spark plugs would have been changed by now at some annual service, unless they are meant to last seven years? I'll ask them to check, but suspect it might not be it. The receipt says Magnatec oil, whatever that means.

[mudyf0x]

magnatec is a 10-40w oil, i dont think thats the right type to be honest , think u should be using 5-40 fully synthetic

[anewman]

I'm no expert but the lambda values are under spec, so I'd have thgought the lambda probes would be the first place to look?! Especially since the ECU logged a fault on one! That should bring down the fuelling and emissions.

[jeremiah]

magnatec is a 10-40w oil, i dont think thats the right type to be honest , think u should be using 5-40 fully synthetic

It was the same the last few times though, so it would not be the sole cause. If they have really been putting in the wrong oil, it would be a worrying sign of incompetence. Is there an authoritative way of finding out what oil is appropriate? It's not as if I can ask them :-)

[mudyf0x]

It was the same the last few times though, so it would not be the sole cause. If they have really been putting in the wrong oil, it would be a worrying sign of incompetence. Is there an authoritative way of finding out what oil is appropriate? It's not as if I can ask them :-)

drivers handbook states oil must meet vw spec 503 spec, and im almost certain that magnetic is not compliant...

[jeremiah]

I'm no expert but the lambda values are under spec, so I'd have thgought the lambda probes would be the first place to look?! Especially since the ECU logged a fault on one! That should bring down the fuelling and emissions.

The probe that logged the faults has been replaced already. I think it should be fairly easy to find out what the problem is with the correct equipment: the lambda probes should be producing swings (measurable using a voltmeter) and if that is fine then it is either something before the cat or the cat (can be determined by measuring its effect on the exhaust gas by measuring CO before and after). The main question is whether it is worth spending effort on this, or whether it would be cheaper just to replace the cat because it is supposedly the likeliest cause.

[rum4mo]

Well, just my two pence worth, a tech has said that cat failures on 1.2 engines are common(ish) - use search here and on www.seatcupra.net and you will see that this is indeed the case, the first lambda probe(S1) is the control probe and the second one (S2) is the monitor probe - ie checks that the exhaust "quality" post cat is okay - just in case you did not know that!

[jeremiah]

drivers handbook states oil must meet vw spec 503 spec, and im almost certain that magnetic is not compliant...

I think that is only with variable service intervals. Mine are fixed, so acceptable oils include VW 501 01, VW 502 00, and VW 504 00. I don't know if Magnatec complies.

[rum4mo]

One thing to remember, Magnatec is available (to trade in bulk) at different "weights" than 10W-40 (I seem to remember) - so don't assume that 10W-40 was (wrongly) put in it..

Edited 19 May, 2010 by rum4mo

[jeremiah]

One thing to remember, Magnatec is available (to trade in bulk) at different "weights" than 10W-40 (I seem to remember) - so don't assume that 10W-40 was (wrongly) put in it..

The receipt actually mentions 10w/40. However, if you scroll down to the bottom of the following link, it supposedly complies with VW 501 01 http://www.opieoils.co.uk/p-752-castrol-magnatec-10w-40-part-synthetic-engine-oil-acea-a3b4-new-product.aspx

[jeremiah]

Duplicate post (and sorry for not mentioning exactly what the receipt said to start with)

Edited 19 May, 2010 by jeremiah

[martinch]

It was the same the last few times though, so it would not be the sole cause. If they have really been putting in the wrong oil, it would be a worrying sign of incompetence. Is there an authoritative way of finding out what oil is appropriate? It's not as if I can ask them :-)

Here ya go:

http://ew5.earlweb.com/recommendations.php?site=44&keywords=fabia+1.2&vehicle=7595

Platinum is 5w40 ("PD oil"), Longlife III is 5w30.

(if you haven't heard of them, Quantum are owned by V.A.G.)

[jeremiah]

I have a 2004 Fabia 1.2 6v that has failed an MOT retest on emissions:

Just in case it helps anyone, the emissions have returned to normal after the cat was replaced. Many thanks to all who replied.