Technical Just Failed MOT on Emissions "just" .. help needed.

[bigfathairybiker]

Hi,

I've just put my Stilo 1.6 throu an MOT.

Emissions passed HC and CO but failed Lambda reading.
mine was 1.07 and the limits were 0.97 to 1.05 or something like that.

History since I've had the vehicle in the last year are...
Replaced Postcat sensor to resolve bad idling and red light.
Replaced one coil pack when started running really badly... now runs better than ever.

Should I just go out and buy precat sensor or could there be something else?

Ta.

Mark

 

[Citizen Smith]

I would 1st suggest that use put an injection cleaner in the fuel tank and take the car on a long roadtest ensuring that high revs of the engine are achieved. It may be a lazy lambda sensor and is not getting hot enough to work properly.

 

[VII CKS]

Right this could be the sensor, you can try cleaning the sensor. Best bet is to change the CTS (coolant temp sensor) this can sometimes if old/not included in service as a part can cause emission problems. Then put a shot of Redex in a full tank, check your airfilter element is clean, before the MOT test, give it a long drive to warm up the CAT, then a thrash in second gear before approaching the station just to clear any carbon out the exhaust etc, don't over rev the car though.

If it fails again then it will be a lambda, easy enough to change yourself and can get the part online however try stick with a proper Fiat part, patent parts are rubbish and my universal one on another car I have gave up after a year, and still cost me quite a bit!

 

[12[X]]

lol easy to change.. unless it rusts/welds in

 

[arc]

on an emissions test high lambda reading means that there excess O2 in the exhaust, it is a reading taken from the probe in the end of the tailpipe and not by the sensors wired to your ECU.

what kind of condition is the exhaust system in, because a small leak will pull air into the exhaust - leading to a result like this.

with the engine running, stick your hand over the tailpipe - can you hear it leaking from anywhere down the system?

 

[Morty Mort]

with the engine running, stick your hand over the tailpipe - can you hear it leaking from anywhere down the system?

It will leak from the backbox as it has a drainhole there (lower front). Put a finger there aswell.

 

[Deckchair5]

on an emissions test high lambda reading means that there excess O2 in the exhaust, it is a reading taken from the probe in the end of the tailpipe and not by the sensors wired to your ECU.

Absolutely. The emissions test "lambda" has very little to do with the engine exhaust lambda sensors. It's simply saying too much oxygen in the exhaust tailpipe and will often be an exhaust leak from the cat to the back box. If the other emission figures HC CO etc are correct then the engine lambda sensors might be fine. Need ALL the emissions figures for analysis and not just the emissions lambda. Lambda simply means "balance"

 

[sixpotman]

Sound like the testers being a bit
Is it a Fiat Garage?

My old car was like that lambda was way out
but Emissions were fine - MOT tester explained the problem
but said as the emissions were fine he'd still pass the car.

John

 

[medley75]

Stilo MOT emissions failure

Hello, new to the forum, hope someone can help.
I have a 1.6 16v Stilo (52 plate) and it has failed it's MOT emissions test - on certificate it says - exhaust emissions Lambda reading after 2nd fast idle outside specified limits.
The fails are - Fast idle test, lambda, actual value 1.266, fail
Fast idle test, lambda, actual value 1.223, fail

The garage tried a new complete exhaust - still fail
tried cleaning spark plugs - still fail
tried new lambda sensor - still fail

In fact the garage could not pinpoint the fault as to why the emissions were still failing.

P.S. have had problems with my MAP sensor recently, was replaced and didn't seem to correct problem - different garage just did a flash update and problem (cutting out) seems better, but not 100% sure that all is well still as on MOT test it states - engine idle irratic, cuts out, surging at idle.
Maybe this is affecting the emissions somehow ?

Any suggestions will be much appreciated or if anyone knows a decent garage in the manchester area that could diagnose the real fault.

 

[Citizen Smith]

Re: Stilo MOT emissions failure

One thing to try would be to clean the throttle body as if it was coked up slightly it can throw the mixture / readings off sometimes.

Make sure that the engine is also properly warmed up as well as the cat convertor could be a bit lazy untill its given a good blast - give it a good road test with some high revs before checking the emiisions again.

 

[sixpotman]

Re: Stilo MOT emissions failure

Could you post all the other readings as well
it may point in the right direction then.

Lambda can be out but emissions still ok
up to the tester then if he passes the car for
emissions.

John

 

[medley75]

Re: Stilo MOT emissions failure

full readings are -

Fast idle test - CO - 0.017% , (limits <= 0.300%) PASS
HC - 17ppm , (limits <= 200ppm) PASS
lambda - 1.266 , (limits between 0.970-1.030) FAIL

Fast idle test - CO - 0.027% , (limits <= 0.300%) PASS
HC - 9ppm , (limits <= 200ppm) PASS
lambda - 1.223 , (limits between 0.970-1.030) FAIL

Natural idle test - CO - 0.015% , (LIMITS <= 0.500%) PASS

 

[sixpotman]

Re: Stilo MOT emissions failure

Knicked off another forum perhaps a MOT tester can verify

CO is good, HC is good. Primary lambda should be fine.

Calculated lambda value being too high would mean it's running lean, but in this case means you have an exhaust leak after the primary lambda sensor that's allowing oxygen from the ouside into the exhaust system and it picks up on the sniffer equipment.

Sniffer lambda value is just calulated from the distribution of the % of gasses (CO, CO2, O2, HCx) in the exhaust gasses and NOT a reading from the lambda sensor itself.

If a leak were present in front of the sensor you'd get high CO values as the ECU would think it's running lean and dumping in fuel. This would give you an 'impossible' result with a high lambda reading (lean) and high CO (rich)..

Possible air leak?

John

 

[Dom_S]

Re: Stilo MOT emissions failure

I have the exact same engine and age Stilo Multiwagon and mines also failed the MOT!

So far I have one very knackered CAT and a very large bill...the inside has pretty much melted I've been told!

Can you let me know how you get on?

 

[medley75]

Re: Stilo MOT emissions failure

Hello again, just a quick update - after being passed from pillar to post by various garages, am now going to try a petrol injector cleaner, then re-test, if that fails then a new exhaust (as I'm told by another garage that my cars exhaust had not been changed for testing as previously told), then re-test, if that then fails them I'm told it's the actual Lambda sensor/s (£137 top, £172 bottom)- they won't know which one until they investigate further - oh and this could run in hundred's on the repair as they are in a very hot area on the car and have been known to get virtually welded in.
Can things get any worse ..............

 

[Most Easterly Pandas]

Re: Stilo MOT emissions failure

oh and this could run in hundred's on the repair as they are in a very hot area on the car and have been known to get virtually welded in.

I'd go to a different place mate. They obviously don't know what they're doing as any reputable garage will know how to easily remove a lambda sensor, and should even have a tool for doing it.

 

[sixpotman]

Re: Stilo MOT emissions failure

Stilo 1.6 lambda universal fit under £46 including vat and delivery
http://www.gendan.co.uk/oxygen_lambda_sensors_Fiat_Stilo_1.6i.html

NTK around £65

For supply of the lambda sensor sometimes they can
weld themselves to the exhaust plumbers stilson if you
you can get in there to use them.


Exhaust could be the problem if it has any holes
it will make the lambda reading high.

John

 

[chucky101]

failed MOT because of emissions!

My stilo has failed its NOT for high emissions, this is what the certificate said:

EXHAUST EMISSION CARBON MONOXIDE CONTENT AFTER 2nd IDLE EXCESSIVE [7.3.2B]

EXHAUST EMISSION CARBON MONOXIDE CONTENT AT IDLE EXCESSIVE [7.3.2c]

what can i do?? will i need to change the catalytic converter??

help!

 

[Ffoxy]

Re: failed MOT because of emissions!

My stilo has failed its NOT for high emissions, this is what the certificate said:

EXHAUST EMISSION CARBON MONOXIDE CONTENT AFTER 2nd IDLE EXCESSIVE [7.3.2B]

EXHAUST EMISSION CARBON MONOXIDE CONTENT AT IDLE EXCESSIVE [7.3.2c]

what can i do?? will i need to change the catalytic converter??

help!

Calm down first!
When was it last serviced... did it get a new clean air filter?
Dirty old oil doesnt help either.
Nor do old spark plugs (if its a petrol as you dont say).
If a service is due do one, if not and all is good service wise try running some injector cleaner through it. A good thrash before an MoT never usually hurts if the car does a lot of short slow journeys.

If all that fails you might have a duff sensor somewhere but try the basics first IMO.

 

[Deckchair5]

Re: failed MOT because of emissions!

The actual recorded figures are a great help to pin down the fault and eliminate others so always get them and put them in your posts

But if, say, the CO reading is way above 0.3 for 1st and 2nd idle test then, assuming air filter and sparks to be in good shape, the first step would be check out the pre cat O2 sensor. This leans off the fuel when the engine is in steady rpm -like idling or any steady speed state- so without that it'll be guessing and over fuelling in a big way. A sudden noticeable drop in fuel economy would also be a clue