Xantia MOT Emmissions

Evodad · Post by **Evodad** » 20 Nov 2006, 18:58

Took my '94 170k miles 1.8 8V petrol Xantia for MOT; fail.

1. New front disks & pads reqd, "fair cop guv": Now replaced.

2. Emmissions:-

Fast Idle
CO <.30% actual 0.06%
HC <200ppm actual 105ppm
lambda 0.970 - 1.030 actual 1.138 FAIL

2nd Fast Idle
CO actual 0.00
HC actual 33ppm
lambda actual 1.119 FAIL

Natural Idle
CO <0.50% actual 0.18%

Got home, looked at last year's numbers, they're similar & it passed!
Noticed that the lambda limits last year where 0.970 - 1.150!
Also noticed that the limits used this year were for a 1900 BX, not a Xantia.
Will point this out when I go back Wednesday, the guy's OK, so I should be alright.

Point 1. Are my numbers OK for the year & mileage?
Point 2. Ensure they use the limits for the correct car!

Richard Gallagher · Post by **Richard Gallagher** » 20 Nov 2006, 20:22

By the sound of it you have good grounds for an appeal on the basis that the wrong data was entered prior to the test being carried out. I'd speak to the garage/mechanic concerned as it may have been an honest mistake.

Post by **CitroJim** » 20 Nov 2006, 21:39

Seems a bit harsh to me to fail it on a lambda reading when the actual emissions that matter are well within a pass. CO is fantastic and HC is good too..

What exactly is being measured by the lambda reading at MOT time? Is it the vehicles own lambda sensor or the one they stick up the tailpipe as part of their emission check?

If the latter then it's running just a touch on the rich side, hence perhaps the slightly elevated HC figure. A new air filter element and a good clean of the inlet tract may be an idea before the retest..

Intersting about using BX figures for the test. I don't recall any BX having such sophisticated engine management that included a lambda sensor.

Evodad · Post by **Evodad** » 20 Nov 2006, 22:09

Thanks for the advice & comments.

Replaced the air filter & wiped out the inlet tube yesterday, ready for when I take it in again on Wednesday!

I don't know about the BX, it just what it says on the top of the readout from the Sun machine, "BX Series", capacity in cc "1900".

The tester's a "regular guy", I've used him a few years now for MOTs, reckon it was a genuine mistake.

It would have failed anyway on the brake disks, so I'll hopefully sort it out on Wednesday.

Thanks,
Roy.

Post by **philhoward** » 20 Nov 2006, 22:11

citrojim wrote: Intersting about using BX figures for the test. I don't recall any BX having such sophisticated engine management that included a lambda sensor.

Very, very late BX's had Lambda Sensors and (I believe) Cats... I had a 92 (J) BX GTi which was only just pre-cat (by weeks looking at the RP number) and ran Motronic MP3.1

wheeler · Post by **wheeler** » 20 Nov 2006, 22:24

citrojim wrote: What exactly is being measured by the lambda reading at MOT time? Is it the vehicles own lambda sensor or the one they stick up the tailpipe as part of their emission check?

The lambda measurement is taken from the exhaust tailpipe

citronut · Post by **citronut** » 21 Nov 2006, 09:47

wheeler wrote:
citrojim wrote: What exactly is being measured by the lambda reading at MOT time? Is it the vehicles own lambda sensor or the one they stick up the tailpipe as part of their emission check?
The lambda measurement is taken from the exhaust tailpipe

yes but its is reading what the cars lambda sensor is doing,
Roy
why dont you just go back to the testting station and point out what they have done and ask them if they could just put the car back on there machine to chek the corect values for that car before you book it in for the retest
regards malcolm

Post by **RichardW** » 21 Nov 2006, 12:30

You can't actually measure Lambada - the 'lambda' sensor on the car (and presuambly in the mot analyser) is actually an oxygen sensor, and the lambda figure is calculated from the oxygen present in the gas. The lambda figure on the MOT readout is by the EGA, and has nothing to do with the car's sensor.

I think a high lambda = too much oxygen, ie it's running a bit lean, hence the low CO and HC figures.

My Dad had trouble with the emissions on his 93 1.8 8v at it's first MOT (Lambda too high I think) - this was 'fixed' be removing the ECU and cleaning the pins. The output from the lambda sensor is pretty small, so a small amount of corrosion can lead to an 'off' reading on the MOT EGA.

citronut · Post by **citronut** » 21 Nov 2006, 14:12

when the lambda reading is out of tolerance for MOT purposes it usualy indicates there is a fault with the lambda sensor on the car or the cat,i have known people to remove the sensor from the car a give it a good blast out with carb cleaner and refit it then gat a pass on the MOT
regards malcolm

Evodad · Post by **Evodad** » 25 Nov 2006, 10:40

Just as a postscript.

With new front discs & pads fitted, took my Xantia back for it's retest.
With the emmissions tester now showing the correct limits for the car & engine, these where the results:-

Fast Idle
CO <0.3.% Actual 0.00% Pass
HC <200ppm Actual 12ppm Pass
Lambda 0.970 - 1.150 Actual 1.126 Pass

Natural Idle
CO <0.50% Actual 0.09% Pass

MOT; PASSED

That's one little worry over for the next 12 months.

Post by **CitroJim** » 25 Nov 2006, 11:27

Result

Homer · Post by **Homer** » 25 Nov 2006, 15:34

citrojim wrote: Intersting about using BX figures for the test. I don't recall any BX having such sophisticated engine management that included a lambda sensor.

I had a K plate 19TZi with a cat, there was also a 1.6 injection with a cat toward the end of production. I believe some European markets got a 1.4i.

On subject. I have seen a high lambda reading caused by a small leak in the exhaust system between the downpipe and manifold.

AndersDK · Post by **AndersDK** » 25 Nov 2006, 16:22

The BX cat subject :
Sweden got cats on all cars '88 on by legislation.
In DK we had cats on all cars from '90 on also by legislation.
I have no records on Norway or Germany, but believe its much the same years they got cats too.

Meaning all cars got some kind of either mono or multipoint engine management by the same years to control the emissions.

citronut · Post by **citronut** » 25 Nov 2006, 16:47

Homer wrote:
citrojim wrote: Intersting about using BX figures for the test. I don't recall any BX having such sophisticated engine management that included a lambda sensor.
I had a K plate 19TZi with a cat, there was also a 1.6 injection with a cat toward the end of production. I believe some European markets got a 1.4i.

On subject. I have seen a high lambda reading caused by a small leak in the exhaust system between the downpipe and manifold.

yes that can cause hight lambda reading,as its introducing extra oxogen into the system after the burnt gasses leave the engine
regards malcolm

davetd · Post by **davetd** » 26 Nov 2006, 20:15

AndersDK wrote:The BX cat subject :
Sweden got cats on all cars '88 on by legislation.
In DK we had cats on all cars from '90 on also by legislation.
I have no records on Norway or Germany, but believe its much the same years they got cats too.

Meaning all cars got some kind of either mono or multipoint engine management by the same years to control the emissions.

Best stick to diesels then