MOT Failure - Emissions

cannugec5

I am amazed at this. I always thought that the date the MOT was performed on took  precedence, ie the most recent MOT applied, regardless of expiry date. 

[Deleted User]

Just throwing it out there, the old Italian tune up trick may well get the car through the emissions test, but it's not a long term solution. Modern cars should run fairly clean in an conditions, even with the engine started from cold.

There are many things that can lead to emissions being outside of tolerance. Most of which are covered in a routine service and include things like oil change (yes, your engine oil is part of emissions control in a modern car), fuel and air filters, or failing spark plugs. A hole in the exhaust can also lead to emissions problems, depending where it is. If its before the o2 sensor then the ECU will think the engine is running lean, and start increasing the fuel supply, leading to incomplete burn. But a hole in the exhaust should be spotted before it gets to the emissions test, if they do that last (our local garage does, but not sure if that's the norm or just how ours does it).

A full service would typically include change of filters and fresh oil. These items alone will usually clean up the burn, while also making the car much nicer to drive, and as this is a money saving forum, it's worth mentioning that it's likely to save money over the year, depending how much you drive. 

[Deleted User]

I use Redex regularly and fill up with branded diesel and my 64 Focus TDCI runs sweet as a nut and passes every emissions test. Only problem is the DPF keeps blocking.   

A_Lert

cannugec5 said:

I am amazed at this. I always thought that the date the MOT was performed on took  precedence, ie the most recent MOT applied, regardless of expiry date.

No. First remember that your car must be roadworthy, always. An MOT pass doesn't prove it's roadworthy and an MOT fail doesn't prove it's not. So the existing MOT remains valid and if there are no dangerous faults you can carry on driving.

Example MOT fail items that wouldn't make the car non-roadworthy: broken passenger seats or seatbelts, broken ABS, temporary spare tyre fitted (provided it's got proper pressure and tread).

AdrianC

PieMistress said:

oh_really said:

At the point of test, the engine needs to be at full operating temp else there are possibilities of poor readings being taken.

Looking at the first failure emissions report it said the engine temp was 83C - does that sound about right? 

The coolant was up to temperature.
That doesn't mean everything else was fully hot - oil temperature tends to lag a LONG way behind coolant, for one. Most importantly here, exhaust temp lags, too.

PieMistress

I am learning lots here - thank you!  Ok, so if it fails again on the emissions I will head over once this "storm" passes mid week and take it out for an hour then go straight back to the garage, rather than leave it (as I have had to do on the past 2 occasions it has failed).  It was serviced last August and with having to "stay local" the drives haven't been more than about half an hour since the last MOT.

[Deleted User]

PieMistress said:

 It was serviced last August and with having to "stay local" the drives haven't been more than about half an hour since the last MOT.

Something is not quite right here. If it was service last August, assuming they did everything in the service schedule and not just the dodgy back street 'service' where they just top the old oil up and charge you £100 for pouring a fivers worth of fresh oil on top of the old oil, then something else must be wrong.

Do you know what was covered in the last service?

Also I can't remember if you said its petrol or diesel.

What else was on the fail sheet from the MOT?

How does the car sound and feel to drive? Any extra noise, does it drive smooth, is it as responsive as before, any weird flat spots or misfires etc?

If it's diesel, it is possible that the lack of good runs out might have sooted up the o2 sensor in the exhaust, in which case the old Italian tune up might be all it needs, but I'd be skeptical, and wouldn't choose that as my first option, without considering everything else. The reason being, there are lots of things that can be starting to need attention that can cause it to fail on emissions, and left untreated, that emissions problem can turn into a breakdown.

PieMistress

IT PASSED ! 
I really do appreciate everyone who fed back their thoughts and helpful advice. Had I not posted on here I wouldn't have known how long to take it out for at the weekend and really, what to do with it once I was out on the dual carriageway.
It hadn't failed on any other points bar the emissions.  However, I will keep an eye on how the engine feels/sounds and make an effort to give it a more regular longer drive now that things are - fingers crossed - easing up.   

happybagger

Good news.
Next year, make sure it's had a few decent runs prior to the next test.
Contrary to an earlier post, the idea of "thrashing" the engine doesn't strike me as the best option - the DPF needs to burn off the soot which is done at highest temperatures; high revs yes, but maximum revs beyond the red will more likely burn more diesel without increasing the temperature.
At least that's what I've found with the data from my CR diesel