Possible Failed MOT Cause

Bunceless_Earner

Hello,

Sorry this is a bit of an essay but our car has just failed its MOT (we use Luton Borough Council MOT testing Station always reliable and honest). The car is a 1999 Peugeot 206 1.1 Petrol.

It failed on a couple of things CV joint gaiter insecurely mounted to housing (not concerned about this), however it also failed exhaust emissions Carbon Monoxide and Lambda Reading (they tested emissions twice, to rule out a rogue result first time).

The reason I'm asking for advice and opinions is that we got most of the exhaust system replaced only 3 weeks ago, the parts replaced were the rear silencer box and Catalytic Converter!

Last year it passed with flying colours i.e. CO emission 2008 = 0.10% 2009 = 0.46%!!!

We used our local garage to get the exhaust changed, and I'm pretty sure it's a unbranded exhaust manufacturer, as after we picked it up the tail pipe poked out further than the bumper and we asked if that was OK/safe, they simply cut off the excess!

The MOT tester saw it was an new exhaust and didn't know why it might have failed. Does anyone have any thoughts/suggestions/ideas as to whether this "new" exhaust could have caused the problem?

Thanks in advance.

Pew_Pew_Pew_Lasers!

There shouldn't be any carbon monoxide coming out of a catalytic converter.

Bunceless_Earner

The max permissable is 0.30%

The actual test numbers are as follows:

Eng Oil Temp = 82C

Fast Idle Test

CO level = 0.35% - fail

HC level = 100ppm - pass

Lambda = 1.04 - fail

Second Fast Idle Test

CO level = 0.46% - fail

HC level = 101 ppm - pass

Lambda = 1.06 - fail

Natural Idle Test

CO level 0.45 - pass

swiftnick

Going on what you've posted I would probably think the Lambda switch is at fault.

Nick

(MOT tester)

Bunceless_Earner

Here's a bit more info to put you to sleep.

The car does only do low mileage, ~4000 a year, and mostly short runs e.g. sprogs to school, shopping etc... (wife’s car) which I do all the easy stuff on, no space or time to get more stuck in, other than when broke!

Oil was changed a year ago almost to the day. Was intending to change it before the test, but no time and it looks pretty clean and viscous (by my untrained eye).

Other than the exhaust blowing like Miles Davis (it was also corroded around Cat), it has been running fine.

The previous cat was replaced 5 years ago, I don't know if that was a genuine part either, as it was done just before we bought the car of friend, after it failed it's MOT test. Only 5 years, isn't that a bit premature, or are short journeys taking their toll?

To add a bit of detail to the exhaust replacement, after it was fitted (and the tail chopped!) my wife said "it sounds too sporty, almost like it has a hole in it", I had a look at it and it was blowing on the joint nearest the Cat, (it was a really cold day and it was really easy jet of exhaust gas blowing down onto the road. I took the car back and the garage admitted that they had not put sufficient sealing compound around the join. The was yet another subtle blowing noise, where the front pipe joins the intermediate pipe, they said it wasn’t too bad and tack welded it, they showed me where they had done the job, it looked OK, but I guess it's prone to go again. Although I can't hear or see it blowing anymore (I've not got under the car, no ramps to check it, it still sounds throaty/sporty, which I've put down to the rear silencer being larger than the original, but now I'm not convinced. Now that it’s also failed on emissions I’m wary of everything.

Hintza

I know a garage that turns a lot of What about a wee tune up(older) cars to run on a leaner mixture for the emissions test.

Bunceless_Earner

Hello Hintza,
Not sure if your reply is in jest or serious i.e. Getting "a wee tune-up" will do the job???
Cheers.

manda1205

Get a totally different garage to check the exhaust if thats what you think the problem is. Find someone who has recommendations from family or friends. Did you tell the garage who fitted the exhaust it has failed on its MOT? As Swiftnick says also, it still could be down to the lambda too. Regardless of how many times you check and re-check the exhaust, if this is the prob its gonna have to be changed, and can be pricey too. Not sure of cost on a peugeot.

kaya

ill go with a faulty lambda sensor or perhaps something as simple as changing the air filter, when was it las done?

Pssst

When it comes to emissions,the exhaust system is only a part of the issue. as far as im aware,in most cars the lambda probe lives in the exhaust manifold between the engine and the cat. It provides an input into the ECU which is then used to make minor modifications to combustion parameters eg air/fuel ratio. It can only make a limited range of adjustments before the issue that it tries to correct is out of range. there may be other issues which need specialist fault finding/code reading of the ECU etc.

Hintza

I have just re-read my original post it was nonsense think I typed new stuff in the middle of the sentence. So let me try again.

One garage I know tunes the car down to run on a leaner mixture to pass the test.

However a wee tune up might be all it needs.