MOT Fail Emissions

tomsolomon

OK quick question...
Can a mechanic have a good idea as to why a car failed an emissions test just by looking at the the read out?

Mine just failed, I have been mooching round the internet and most seem to point to similar problems like cat failure, lambda failure, leaking exhausts and breather pipes, most seem to point towards needing a good service. The cat was replaced with a brand new unit last year, so unless this was a faulty unit I would imagine it would still be in good working order. But I wanted to get a second opinion before I end up having to take the car to Peugeot and stick it on their computer and fork out £95 just to find out what's wrong with it.....

The car is a 1.8l petrol Peugeot 406 on an N plate and passed with flying colours apart from the emissions, which read as follows...

Carbon Monoxide content after 2nd fast idle excessive....
Lambda reading after 2nd fast idle outside specific limits....

Measurements

Engine oil temp min 60 deg C -- cooling fan

Fast Idle Test Failed

Engine speed 2500-3000 rpm Manual check Pass
CO <= 0.300% 0.789% Fail
HC <=200 ppm 132 ppm Pass
lambda 0.970-1.030 1.051 Fail

Fast Idle Test Failed

Engine speed 2500-3000 rpm Manual Check Pass
CO <= 0.300% 0.758% Fail
HC <= 200 ppm 174 ppm Pass
lambda 0.970-1.030 1.051 Fail

Natural Idle Test Passed

Engine speed 450-1500 rpm Manual Check Pass
CO <= 0.500% 0.396% Pass

This is exactly how it reads on the test sheet apart from the spaces obviously...:P

OK that's the technical stuff out the way, I know these cars are capable of 30mpg, I'm currently doing less than half that, if this is any indication of the failure???

Can someone help please before I end up spending loads at Peugeot?
The fuel bills are crippling us already without having a huge bill from Peugeot...

custardy

could be a few things TBH
these things can be a pain and its often why folks get the codes
BTW you might find non dealers have the equipment to read the codes for less
I seem to remember these cars can have dodgy map sensor connections leading to these problems
Its under the inlet manifold
if you reach under find it
give the connector a bit of a wiggle with the engine running
if the engine revs fluctuate/splutter then it points to a dodgy map sensor/connection

I dont know these engines well though,even though my own car has it

mikey72

Could be a faulty lambda sensor.

KillerWatt

I'd be looking at the lambda sensor as the first port of call.
If it was a shagged MAF meter, you'd know about it the minute you try to start/drive it.


PS
The lambda sensor will be in the exhaust downpipe section.

skiddlydiddly

If you overfuel then you Co will go up and yours has so it could be that.If you are only getting 15mpg and are driving normaly I'd say you are massively overfuelling.
You're better off searching the Peugeot forums really as no doubt this topic will have been covered many times before and someone will have already spent the money finding out what the problem could be/was.

anewman

KillerWatt wrote: »

I'd be looking at the lambda sensor as the first port of call.
If it was a shagged MAF meter, you'd know about it the minute you try to start/drive it.

They can also lose efficiency over time leading to over-fuelling, before being completely shagged

custardy

KillerWatt wrote: »

I'd be looking at the lambda sensor as the first port of call.
If it was a shagged MAF meter, you'd know about it the minute you try to start/drive it.


PS
The lambda sensor will be in the exhaust downpipe section.

anewman wrote: »

They can also lose efficiency over time leading to over-fuelling, before being completely shagged

yup except i believe these use a MAP sensor over MAF

liz_uk

As crazy as this sounds.. my peugeot 206 Diesel failed on emissions, I had it tested at a local garage and the guys were great.. they drove it up and down the bypass a few times, came back, re-tested it and guess what - It passed!!

They said that this is quite common !

custardy

liz_uk wrote: »

As crazy as this sounds.. my peugeot 206 Diesel failed on emissions, I had it tested at a local garage and the guys were great.. they drove it up and down the bypass a few times, came back, re-tested it and guess what - It passed!!

They said that this is quite common !

yup it works,its a problem with cars that do lots of short journeys nad city driving
you need to give it a good rag and motorway speeds to get everything nice and hot

tomsolomon

There is a problem with fuel consumption 15mpg, I can smell the unburned fuel coming from the exhaust......
I don't think it's just a case of ragging it to clear out the system...

custardy

tomsolomon wrote: »

There is a problem with fuel consumption 15mpg, I can smell the unburned fuel coming from the exhaust......
I don't think it's just a case of ragging it to clear out the system...

The problem is Tom bar loose connections(see my first post)
you are looking at replacing parts
that means money
so it maybe worth getting the codes read to at least get an idea of whats wrong
its could be lambda,temp sensor,injector problems,MAP sensor faults or something else
cant really diagnose it 100% via the forum