I have a 1.9 TDI mark 2 Octavia.  I have had it six years and in four of them, it failed on the emissions/smoke test (exceeded limits etc).  On the first three, a cleaning additive and a run round solved the issue.

 

However not this time - my MOT was yesterday and I put in Redex diesel MOT treatment about five days before, I would say it did 60 miles before the test.  I also took it out for 20 minutes before dropping off to tune up.

 

The emissions however came out at 2.8 (max is 0.8).

 

So as recommended, put in some Forté Diesel System Cleaner and really tuned up.  Up and down the M4, 2nd gear up to 50mph, third up to 70mph.  Basically on the red line (4.5 revs).

 

In total today it has had about a two hours such driving over a four hour period, but this could only get the result down to 1.3.

 

There were NO other failure items, just emissions.   Performed well today, nippy car.

 

But... I'd have thought all that treatment and tuning should have got it to target.

 

Would you try anything else?  If so, what?  The tester said perhaps it needed a regen but at this garage, which is really well recommended locally, they don't do emissions work.

 

Would you get it tested elsewhere?  Or are all tests the same or close enough?

 

Or would you scrap an otherwise fine car - maybe as this could indicate an issue somewhere?

 

Cheers.

@JamieH86 - You don't say which year this is, but a 1.9TDi may well not have a DPF to regenerate!

Sorry, hate to miss info!  

 

It is 2005, don't think it has a DPF but I am not expert enough to know if "regen" specifically refers to DPFs or has a wider diesel meaning, too.

Could be the MAF sensor has gone off. Genuine one was about £100. Cheaper ones about £45.

Ideally you need to get it plugged in to diagnose before throwing cash at it. It could be a simple or cheap fix. Does it use oil? Smoke?

The oil level was sitting nice at the medium line before the MOT, no loss since I last looked (few months?).

 

No smoke at all either.  I was looking in the mirror constantly for some, but there was none!   There was some soot on the back of the car though, or at least something grainy and black mixed in with rainwater.

Apparently Archoil Diesel additive is good. Also when was air filter last changed? Maybe a new one or remove it completely for the test.

Use Diesel Supreme for a bit. My 2.0tdi actually costs less per mile to run on that stuff according to my fuel app.

It was serviced in June so filters and oil about 5/6 months old.

 

The MOT expires today so I can't really do any more running around in it.

Take the air filter out for the test?

 

Where is the target of 0.8 found?

I'd agree with @StonekeeperIt's high, but not over. The comments about it needing a regen make me think they've got it keyed into the system as a newer car. 

 

Generally speaking, and it is a bit approximation:

 

Grey smoke = boost leak

Black smoke = injectors

Blue smoke = burning oil

Billowing white smoke = burning lots of oil, probably via a knackered turbo

Edited 30 November, 20241 yr by StevesTruck

Different Car brand but same problem. This poster eventually passed.

 

https://forums.mbclub.co.uk/threads/mot-emissions-fail-plate-limit-used.266241/

42 minutes ago, JamieH86 said:

It was serviced in June so filters and oil about 5/6 months old.

 

The MOT expires today so I can't really do any more running around in it.

The question you need to ask - was the air filter actually replaced during the last service?

14 minutes ago, Stonekeeper said:

 

Where is the target of 0.8 found?

It's always been tested there for me.

 

Here is the actual result inc target:

 

 

1 minute ago, Warrior193 said:

The question you need to ask - was the air filter actually replaced during the last service?

I mean I can only say, it was supposed to have been!

2 hours ago, Stonekeeper said:

 

Where is the target of 0.8 found?

I was wondering that myself. It might be worth asking MOT place why its 0.85 instead of 3 ?

I assume as its marked applied then its inputed manually. Might have been a fat finger moment when keying in the info to the anylser? If your getting a bit of black soot I reckon check the air filter. Also the temp shows 82 which is ok but wondering if they warmed car up first?

 

Looking at previous years:

 

2023 I have just got a Smoke Check, which was a FAST PASS.  The result was 0.47 and the "normal result" specified (ie the maximum?) is 1.5.

 

2022 failed on emissions; I've got a "smoke opacity analysis", with the car averaging 2.64.    It says "plate value: 0.8".  Test type was turbo.    The retest was a Smoke Check FAST PASS again, with a value of 0.17 against an apparent 1.5 target.

 

2021 failed; another different printout!  Says result was 2.43 and limit applied was 0.8.   Retest same sheet and result 0.4.  The invoice mentions 4-TEC fuel treatment.

 

Don't know if any of that helps!

1 minute ago, Alasdair1 said:

I was wondering that myself. It might be worth asking MOT place why its 0.85 instead of 3 ?

I assume as its marked applied then its inputed manually. Might have been a fat finger moment when keying in the info to the anylser? If your getting a bit of black soot I reckon check the air filter. Also the temp shows 82 which is ok but wondering if they warmed car up first?

 

I was driving it for an hour or so prior to the test, it should have been warm!   Temp gauge said 90, right in the middle.

 

Looking at previous tests they largely seem to be against a 0.8 limit.

But is the testing station applying the correct limit to your vehicle?

Not the best option, but, worth a try, maybe? 

Just take the manufacturer plate off, especially if you're gonna scrap it afterwards... Take it to another MOT station,  and because they can't find the plate they should apply the generic limit, 3 for a turbocharged diesel vehicle. 

That being said i don't live in the UK so no idea if not having that plate will cause any other problems for you. 

I suppose that if you don't re-register the car or do any modifications that would have to be legalized, it shouldn't matter.. 

"So as recommended, put in some Forté Diesel System Cleaner and really tuned up.  Up and down the M4, 2nd gear up to 50mph, third up to 70mph.  Basically on the red line (4.5 revs).

 

In total today it has had about a two hours such driving over a four hour period, but this could only get the result down to 1.3."

 

 

Did you put the full bottle in and how much fuel was in at the time?

 

My Mot tester told me to put a full bottle in half a tank when it failed and it always passed afterwards.

 

I don't think you are far away from passing it's only 0.5 away and you dropped it 1.5 the first time you did it so another similar run could be enough. Don't forget to check the air filter too.

 

I think you are a long way from needing to scrap it.

4 minutes ago, Warrior193 said:

But is the testing station applying the correct limit to your vehicle?

Well this is what the question is.  They're certainly applying the limit that everyone else always has.

 

Luckily I have full history and receipts etc from new.  The first MOT in 2009 applied 3.00.   It passed at 2.62.

 

2011 it dropped to a 1.50 maximum and passed at 0.93.

 

As an aside in 2016 the engine temp was 81 degrees and it passed on 0.07!

 

In 2018, the maximum seems to have changed to 0.8 as that is the first smoke test with that as "plated value".

1 minute ago, Stonekeeper said:

"So as recommended, put in some Forté Diesel System Cleaner and really tuned up.  Up and down the M4, 2nd gear up to 50mph, third up to 70mph.  Basically on the red line (4.5 revs).

 

In total today it has had about a two hours such driving over a four hour period, but this could only get the result down to 1.3."

 

 

Did you put the full bottle in and how much fuel was in at the time?

 

My Mot tester told me to put a full bottle in half a tank when it failed and it always passed afterwards.

 

I don't think you are far away from passing it's only 0.5 away and you dropped it 1.5 the first time you did it so another similar run could be enough. Don't forget to check the air filter too.

 

I think you are a long way from needing to scrap it.

Yeah whole bottle and I topped to half a tank with premium diesel.

 

In fact I should add, it was tested twice today.

 

Took it in after a few hours driving and it averaged 1.6 down to 1.3 on three revs.

 

So I went out for another hour, giving it the red line on dual carriageways etc, and they did one more test where it was 1.4.

 

So seems to be stuck there.

 

Will certainly be looking at the filter.

2 minutes ago, JamieH86 said:

Well this is what the question is.  They're certainly applying the limit that everyone else always has.

 

Luckily I have full history and receipts etc from new.  The first MOT in 2009 applied 3.00.   It passed at 2.62.

 

2011 it dropped to a 1.50 maximum and passed at 0.93.

 

As an aside in 2016 the engine temp was 81 degrees and it passed on 0.07!

 

In 2018, the maximum seems to have changed to 0.8 as that is the first smoke test with that as "plated value".

Are you able to check your actual plated value - is it 0.8?

Plate value is what they should use 'if it can be read'.

The wording in the test manual isn't wonderfully clear though, so the default limit is often mistakenly used. My A4 seems to have been tested to different limits almost in alternation.

3 minutes ago, Warrior193 said:

Are you able to check your actual plated value - is it 0.8?

Where, without wanting to sound like a total banana, would I find it?

1 minute ago, JamieH86 said:

Where, without wanting to sound like a total banana, would I find it?

 

B pillar on driver or passenger door opening normally with the weights.