Mot Emissions Fail On Co Reading, Very High @4.27%

[qwertyuiop7 0]

Check sheet as follows

 

Idle speed - passed

Smoke Level - passed

 

CO 4.27% vol - Fail (limit for a pass is 3.5% vol)

HC 872 ppm - Pass (limit for a pass is 1200 ppm)

 

K reg 1.9 non cat 102000 miles on original engine

 

Mechanic not particularly helpful, says it could be loads of things??

 

He said he tried to reduce it but not succesful.

 

What should i check/clean/buy new first ??

 

Runs okish

Starts well and idles well when cold, not so good when warm tend to rev its nut of when you stop in traffic on a long run and the usual hot staring can be a problem sometimes. Has been running rich for a while, and smells a bit like its on full choke even after a 10 mile run to work.

Fuel economy is well down also

 

Thanks for any help

 

Phil

Edited February 17, 2010 by qwertyuiop7

[Anthony 1,003]

Have you tried adjusting the idle mixture screw? Anti-clockwise 2-3 turns should normally suffice to bring the CO down.

 

Otherwise, usual candidates like ECU temp sensor, replacement AFM, etc - a search will reveal lots.

[The Arch Bishop 0]

Could be your ECU temperature sensor. If it's knackered it makes the engine run very rich. A pretty common fault so have a search on this forum and you'll find lots of info!

[qwertyuiop7 0]

Could be your ECU temperature sensor. If it's knackered it makes the engine run very rich. A pretty common fault so have a search on this forum and you'll find lots of info!

 

 

Tried the search function first, but as i often find with searching a common fault, there is almost too much info.

 

The air flow meter was always the problem on my first 205. (that was nearly 20 years ago and i ran no better from new than my current one).

Tried to find some info on retracking and testing the AFM but all the links don't work anymore, any one with a copy they could send me??

 

The garage has tried to adjust the mixture screw, but i had no effect.

 

Kind of figured it must therefore be a faulty sensor or electrical unit of some sort.

But wasn't sure where to begin??

Probably safest to start with the cheapest bits??

 

Just for my info, is a high CO reading to much fuel and a high HC reading evidence on burning oil from say worn rings or valve seals??

 

phil

[Guest BigErn]

For what they cost, Id chuck an CTS in it anyway so it rules that out.

 

My Cossie was 11% when I stuck the analyser up its arse and its now down to 4.8%. Lucky my MOT tester is a friend

[The Arch Bishop 0]

Agree with above. Coolant Temperature Sensors (CTS) aka ECU temp sensors cost about £16 quid from GSF and are really quick to fit.

 

Recent topic with part number

[Miles 331 1 Cars]

Air Filter?

[woodsy 0]

As said i would reckon check airfilter, coolant temp switch and more than likely needs the airflow meter setting up especially if the mixture screw

isnt altering the reading when you try to adjust

[johnsimister 10]

High HC (ie unburnt hydrocarbons) is due to a rich mixture which can't be burnt completely, or a misfire, or both. High CO and HC together mean an over-rich mixture. If the CO is lowish and the HC high, then some fuel isn't being burnt at all and so is producing no CO, never mind the CO2 that is the product - along with water - of completely burnt fuel.

 

As previous posts suggest, temp sensor (cheap) or AFM (not cheap) are favourites given that you have both high CO and high HC. I've had to replace AFMs on both my 205s in the past for this reason. When the AFM is worn out the mixture screw's adjustment no longer brings the CO with the required range. The legal max is 3.5 per cent CO but that's too rich for the engine to run as it should. About 1.5 is best in my experience for an engine which has lived a little, a touch higher than the one per cent specified by Peugeot. HC should be around 100ppm; the legal limit of 1200ppm is way too high for an XU.

 

Hope that helps

 

John

[The Arch Bishop 0]

A decent second hand AFM can be quite reasonable if bought from a realistic seller. I have a really good spare that cost me £15 from a member on here. There may even be a member of the forum near you that has a spare you can try. It's really worth a go as just throwing expensive parts at a problem is a very frustrating experience. Trust me, I know!

[Bottrill 0]

A decent second hand AFM can be quite reasonable if bought from a realistic seller. I have a really good spare that cost me £15 from a member on here. There may even be a member of the forum near you that has a spare you can try. It's really worth a go as just throwing expensive parts at a problem is a very frustrating experience. Trust me, I know!

 

 

I would go with the AFM. Identical situation with my 1.6 even after I had replaced the CTS.

[qwertyuiop7 0]

A decent second hand AFM can be quite reasonable if bought from a realistic seller. I have a really good spare that cost me £15 from a member on here. There may even be a member of the forum near you that has a spare you can try. It's really worth a go as just throwing expensive parts at a problem is a very frustrating experience. Trust me, I know!

 

Any suggestions on where to get hold of a decent second hand AFM

are there any specalist breakers I should call or is it just a case of a "wanted" advert on the forum?

 

Really enjoy driving the car and plan to keep I for as long as possible so worth spending a few ££ on it.

 

Phil

[dcc 855]

This brings back memories of my first gti. emissions were close to 13%! used to have the print out somewhere

[rubyna 4 1 Cars]

Any suggestions on where to get hold of a decent second hand AFM

are there any specalist breakers I should call or is it just a case of a "wanted" advert on the forum?

 

Really enjoy driving the car and plan to keep I for as long as possible so worth spending a few ££ on it.

 

Phil

 

Hi mate, put a wanted ad up on forum..

Luke