[bingotop]

My 20 year old Pug 306 1.9D failed its MOT recently on emissions.
Suspected it was going to when I heard the 4th, then 5th then 6th test! Anyway didn’t look at the figures until I got home.
They are:
1.86, 0.92, 0.61, 3.20, 0.84, 2.21.
It’s an early (1997) normally aspirated diesel, so the limit is 2.5.
The final result was 2.63, hence declared a FAIL.
My understanding of the test was/is if the average (mean) of the first 3 runs is less than the limit, it is a pass.
If not, you keep testing up a total of 6 runs, taking the average of 3 consecutive runs.
Now the first 3 runs above have an average of 1.13. Well under the limit of 2.5. So why did it do further tests?
Even the last 3 runs average 2.08. No idea where 2.63 comes from!
The tester says its all down to the computer. It works out the mean etc. Says he has tested many diesels since the update. But have they been normally aspirated pug 306s?
Where do I stand? I can complain to VOSA, but believe they will just get me to have it retested elsewhere.
I have put some redex cleaner in tank. Will also change engine oil.
It already had an Italian tune up before the test.
I suspect a software bug as tester said machine had update in May this year.
Not really happy to put old girl through another 3 non load thrashes.
BTW the tester said while there was no visible smoke, he noticed knocking at high revs, and thought the machine may be taking that into account.

[captaincon]

if it has a plate value displayed on the car he will be going from that this is normally a low figure compared to the default limit ts part of the new regs.if he cant find the plate value then the limit he should use is 2.5 for a non turbo engine

[castrolrob]

the smoke test readings and their sequence make no sense and I supect the pipe fell out halfway thru or was it actually being smoke tested or was the throttle just being blipped to make it look like it?(im assuming its a healthy engine/injection system)as regards your emissions readings a lotta analysers(ours included)make us do a minimum of 4 revs particularly when a couple are above the limit,we get no control over that,we just rev when prompted or the machine wont let us complete the test.

[bingotop]

Car has no plate stating emissions. I witnessed testing and it looked like tester followed instructions from computer. Probe did not fall out.
The main issue here is does the diesel opacity test compare the average of 3 runs to the limit? Yes or no?
If yes, then someone please explain why mine didn’t pass after the first 3 runs.

[Stealth]

Hi bingotop. Do you know if the tester attached an RPM monitor during the test ?

[Paul S]

To get a Fast pass think it needs to be less than 1.5 on the first acceleration, which yours wasnt so it did a further 3 accelerations which on the 3rd you got 3.20 which caused the machine to go a further 2 accelerations.

on a 4 acceleration pass it adds the 2nd, 3rd & 4th & knocks off the drift value.

Dont know the formula for how it works out the average on 6 accelerations, got one in front of me & like yours cant figure it.

[bingotop]

Paul, thats not what i have read. One run to see if Fast Pass. If thats fails a further 2 runs and average of the 3 taken. If over limit, a 4th run. Now 2nd, 3rd and 4th are averaged. The first run is not included. This continues until 6 runs in total have completed and final result should be average of last 3 runs only.

[bingotop]

Been in for retest. Passed this time first attempt. Result 0.78, on Fast pass test limit of 1.5.
However all the fields on the form e.g. idle speed, cut off speed, accel time, holding time are now filled in. On the fail form they were all blank.
Car too old for OBD socket. Donnt know how these were measured??
Tester thought lack of OBD may be issue, as some of this stuff e.g. oil temp would then need to be entered manually.

[bingotop]

Stealth, don’t know if RPM attached for first visit. Fields on form like idle speed etc all blank. For retest, tester had bonnet up, and idle speed etc now recorded. Car too old for OBD, so if these speeds are required, he would have had to attach one as you suggest.

[castrolrob]

one outside possibility,did he enter it as pre 08 non turbo?your emissions sheet shud have the limit it was tested to on the initial fail,part of the update was a lower limit for a lotta cars with post 14 cars for example being tested to a limit of 0.7,post july 08 being 1.50 and with some emissions machines particularly if you’ve been using em a number of years its no trick at all to keep hitting enter on the same buttons you’ve been using for those years and end up with the wrong limit,my gopher did precisely this to a 20 year old mazda bongo friendee,despite being told it had no plated limit and was 20yr old he entered it as 2014 limits for some insane reason,ok it didn’t matter on that one as it averaged 6.50 and as such was a straight fail anyway but you get the idea.

[bingotop]

Castrolrob. Fail sheet has 2.5 limit on it.

[castrolrob]

like I said an outside possibility.its just that the readings youre quoting don’t seem to make any sense,they would normally read in a fairly linear fashion rather than going up and down like a whores drawers and if accurately/properly tested strongly suggest a problem with the engine with pump/injectors being leading possibilities.still its got a test now….

[Aylesbury Jock]

I don’t mean to sound condescending, but would you recognise the plate if you saw it? It has nothing written on it to say it is dealing with the smoke test limits. It is literally just a very small sticker with a small rectangle with a number inside the rectangle, and nothing else. Probably less than an inch in size.

[DB9]

I’ll assume then that the test was carried out after May 20?

Not all gas analysers had been updated at that time and a delay has been allowed until September for all equipment manufacturers to get their software produced and sent to all garages.

In the mean time where the plate limit is readily available that limit must be used, so a car that should be equal to or less than say [0.51] but produces a printout with a result of say [1.01], which is below the [1.5] limit will still fail the test. The printout will say it PASSED, but legally its a fail.

If when conducting the smoke test during the first three runs while depressing the throttle pedal fully to WOT and then immediately off, the tester may notice after the engine has returned to idle that the smoke machine display shows a reading like this [—], this means that the smoke machine recorded a value that was seen outside the operating range, records it but disregards it, hence you will see it on the printout, but the analyser will continue until up to six free runs have been completed because the software has calculated values outside the range.

The customer will not see this on the printout, and the results of the printout when calculating the result could become confusing because of it.

[bingotop]

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