Emissions fail on MOT

[Harry Bloomfield]

And that was the SECOND ice cream tub of gunge that I scraped out of her inlet manifold! (I didn't take a photo of the first one).

Emissions went down from abut 3.5 to 0.98 after that.

Diesels driven hard, rarely seem to suffer from this.

My experience of this, suggests the gunge is of a much drier, less fluid gunge. Once it is deposited, nothing much will shift apart from mechanical scrapping or chemical removal. I have seen EGR bores, reduced by the build-up, to less than 1/3 of the air path through them.

Logically, I cannot see how it might affect the emissions, unless the EGR etc. become very seriously restricted by the gunge.

My workshop manual makes no mention of the possibility of gunge building up, or any need to ever clean the EGR + manifold + intake at all. Being already aware of the problem, when I bought my car - I stripped the lot down and gave it a thorough clean out.

I've kept a close eye on emissions at each MOT, but it has always been so clean, the inspector has thought his tester had developed a fault, the first few times he did the MOT. I note they no longer offer the emission's data printout, following recent MOT's.

 

[ETAF]

i had to clean out the EGR valve on my old saab - easy to get off - but to clean was difficult - used a lot of carb cleaner..... and then it was fine for about 6 mths. In the end i got a patten part from a specialist part dealer , about 1/3rd price and replaced. That was back in around 2010 just before they went bust....
Problem was I stopped doing long trips and just used for very local trips , which diesel dont like
And then had to clean out again in 2018 , along with a lot of other parts, Clutch, alternator, battery , cambelt etc over a year - eventually i got rid of it , as i kept getting a very intermittent engine fault light and my saab specialist spent months trying to resolve, and then said it would cost about 1k to change the fuel pump and other parts.....

 

[Harry Bloomfield]

i had to clean out the EGR valve on my old saab - easy to get off - but to clean was difficult - used a lot of carb cleaner..... and then it was fine for about 6 mths. In the end i got a patten part from a specialist part dealer , about 1/3rd price and replaced. That was back in around 2010 just before they went bust....

You can get a 'bypass' for some engines, which simply blanks the exhaust from entering the inlet, but it increases the Nox.

Which is worse, a badly running engine with a gunged up inlet, creating lots of smoke/ or a clean inlet where the EGR is bypassed and more Nox - is anyone's guess.

 

[ETAF]

You can get a 'bypass' for some engines, which simply blanks the exhaust from entering the inlet, but it increases the Nox.

i looked into a blanking plate - which was available - but a few saab forums reported issues - and the engine fault light was on - so had to remove before a MOT ........
Anyway , just my 2 penny worth, doesnt help solve the OP problem

My son-in-law has an old 1995 Skyline - petrol , which he has to take on a run and thresh to get really hot and warm - to get through the emissions - and if they cant get onto the mot , straight away , as happened at last mot - it fails and then he has a retest.......

 

[Harry Bloomfield]

i looked into a blanking plate - which was available - but a few saab forums reported issues - and the engine fault light was on - so had to remove before a MOT ........
Anyway , just my 2 penny worth, doesnt help solve the OP problem

Yep, which was why I said 'some'. On others, it generates a fault.

 

[trevorbayliss]

Ive checked the oil this morning and i have a bit of black over the top of the dipstick, but there is clearly a black band around the lower half and it finished exactly on half way. So i am assuming this dipstick is showing it is correctly filled. Again I dont do this that often.

I have changed the oil filter as well, but not the air.

As to my driving i really dont drive it that fast. It just isnt that type of vehicle. So the distance the computer tells me i have left in the tank after a fill up is about 720 miles. Now i have been driving harder these kast few days it is saying 540miles. So faster driving has lost me about 200 miles per tank. the question about all this pollution stuff is who is being more green ? Driving slower or driving faster ?

 

[Old Salt]

But you only need to drive it harder every 6 months or so. I use a dpf/injector cleaner every 3 months. Passed the mot on a fast pass emissions test this week with room to spare.

 

[trevorbayliss]

It passed with a 0.17 reading. Stress over. Next time i will drive it hard before the mot

 

[cwhaley]

Nice to get a resolution on this!

As others have said, they don't like being chugged about all the time at low speed.

As for your driving range, you haven't lost 200 miles -- your driving style has just meant the onboard computer has recalculated its estimate of the distance your fuel level will get you. Go back to driving as you were before and it'll change.

It's far better to drive as you were doing with the occasional 'blast' up a motorway to clear deposits. I learnt that driving is so much safer and relaxing at lower speeds.

 

[johnny2007]

Personally, having drained the oil and fitted the new filter I add the new oil till it's between the marks on the dipstick, run the engine, switch off and then add more oil until it is again between the marks.

That's how it should be done.

 

[RandomGrinch]

It's far better to drive as you were doing with the occasional 'blast' up a motorway to clear deposits. I learnt that driving is so much safer and relaxing at lower speeds.

It's the occasional 'blast' that can be important, even for a petrol. A work colleague had a Fiat Panda 4x4 with a 0.9L turbo. He only used it for commuting two miles in city traffic. He blew up two engines under warranty!
Fiat ended up giving him a brand new 500L just to get rid of him!

 

[ETAF]

It's far better to drive as you were doing with the occasional 'blast' up a motorway to clear deposits.

thats exactly what we do - luckily we have to travel approx 50miles on A roads when we visit daughter - so that was once a fortnight at least - and i travel at around 65mph - as that gives us over 50mpg on a 2L diesel, BUT very often on some of these trips every six weeks or so , i give it a blast - and also when leaving and joining the A road

The car also does occasionally remind us with a message on the dashboard - 2012 engine.

 

[Mottie]

I note they no longer offer the emission's data printout, following recent MOT's.

They must issue a printout automatically if the car fails the emission test. They must also issue a printout if the car passes and the customer requests one as well as keeping a copy themselves for three months.

 

[norseman]

I set my level up, so that when parked on the level, in my garage and cold, it is exactly on the full mark. It has a strange dipstick system, in that you have to pull the dipstick out, count to ten, reinsert it, then pull it back out for a true level reading. Just read it on the first pull, and it will show no oil at all.

Our 2006 Mondeo we moved on 3 years ago required a similar procedure. Very little oil showing on the stick if just pulled out. Wipe, replace & pull again resulted in the correct reading.

 

[Belle427]

No need to drive it hard all the time but increasing the revs now and again isn't a bad thing.
Just put a can of forte diesel treatment in it next time a week or two pre test.
Oil and filter plus air filter change too and you should be fine.