Picasso failed emissions

[bamba]

2001 Petrol xsara picasso 1.8 16v ,
Hello all, im in bit of a pickle over my failed emissions mot check,so after bit of advice from any one in the know, im formally from the garage trade so im not clueless but with out proper test equipment its a bit of guess work,any way it has failed on CO% content only at fast idle, 1st atempt was 0.6%,2nd atempt was 0.56% against the max limit of 0.3%, Hydrocarbons was ok at 100ppm,max 200, and lambda reading with in limit at 1.02, although towards the top end limit of 1.03,which i think may be leaning towards a lean mixture, CO% at idle passed ok at idle reading 0.22% and HC also ok.
To summarise only CO% at fast idle is failing.
The garage suggested a new cat,but with out seeing the outputs from both o2 sensors is an expensive gamble,for me anyway.
thanks in advance.

[Mandrake]

I'm no expert but looking at those figures I would say its likely that your cat efficiency is very low, so the garage is probably right, but you would want to confirm it first since cats are so expensive. I've found the MOT test for my 1998 Xantia 3.0 V6 taken last year, bear in mind its a lot bigger engine and older (and is still on the original cat) so you'd expect higher emissions than a 1.8...

My lambda was also 1.02 which just means it was running slightly lean during the test, I've since replaced the oxygen sensor for other reasons but the emissions have not been tested since then...so I don't think theres necessarily anything wrong with your lamba reading.

All the rest are poor though, mine were:

Fast idle:
CO - 0.039%
HC - 15 ppm

Normal idle:
CO - 0.035%

So even though your other figures "passed", barely, they're still approximately 10x higher than mine...

The following page has a good graph that shows the effect on emissions with both changes in lambda and good/bat cat:

http://www.lambdapower.co.uk/TechNotes/Tech-11.asp" onclick="window.open(this.href);return false;

CO and HC with a good cat only really rise significantly if the mixture is really rich - eg low lambda but your lambda is actually too high, so the fact that your CO and HC are both so high means that it probably is the cat.

Is the car running ok ? Pulling well with no misfiring or other symptoms ? If its running poorly you'd need to address that first and then re-test the cat, especially because a misfire or other problem could have cooked your cat in the first place and would do the same to a replacement if not fixed first.

Does your car have a downstream oxygen sensor ? The only way to diagnose the cat for sure would be to graph the upstream and downstream oxygen sensors and do an oxygen storage test. There's a really good video below that shows in detail how to do this and explains the principles behind it:



If the car is not OBD-II compliant (I'm not sure on that year/model) then you'd need to use a Lexia to measure/graph the oxygen sensors. Do you have access to a Lexia ? If not there may be a forum member near you who would be willing to put theirs on your car, check the Lexia sticky thread to check. Where abouts are you located ?

[Ben82]

If the car is not OBD-II compliant (I'm not sure on that year/model) then you'd need to use a Lexia to measure/graph the oxygen sensors. Do you have access to a Lexia ? If not there may be a forum member near you who would be willing to put theirs on your car, check the Lexia sticky thread to check. Where abouts are you located ?

EOBD mandated that all petrol cars from Manufacturing Year 2001 must be EOBD (OBD-II) compliant.. Diesels from 2004.

That video is very interesting and I watched it earlier this morning, the whole Oxygen Storage time being related to Cat life thing is rather interesting. Definitely want to try that on the Lexia to see what it says about mine.

[bamba]

Thanks for getting back, yes the generally drives/starts ok with reasonable mpg, although it does pink a bit, poss a symptom of the o2 sensors trying to lean the engine fuelling down due to a high reading from the down stream o2 sensor (yes it has both).
I had i search last night on the net but couldnt find any thing that described my scenario, with out trying to sound like a know all,im familiar with the o2 sensor graphical outputs etc having spent 12 years at a main dealer garage,and mot'ing ,im just lacking the test equipment since moving out of the motor trade. Although possibly got access to an oscilloscope,which should be able check the sensors,if i can find some wiring schemes.
I keep toying with getting the lexia software but cant quiet justify buying when theres nothing wrong and its always too late in time like these,plus there seams to be some problems getting it to run unless on windows xp.im in derby,il have a look latter to see any one is nearby.
thanks again

[addo]

Does it have the secondary air pump like a 2.0L motor? These can seize up - it'll have a stored fault if so, not sure if it lights the orange dash alert.

[bamba]

dont think so, ive not spotted one, where are they normally located ?

[Mandrake]

If you already know how to diagnose cat efficiency but are just lacking the equipment then we can't do any better at diagnosing it than you, especially when we can't see the car.

A Lexia will definitely show you the oxygen sensor readings, however being a 2001 year I'm not certain that it will be able to graph them. On later models like Ben's 2004 C5 the Lexia can graph up to 6 different PID's at once, however on older models like my 1998 Xantia the Lexia cannot do any graphing at all, just show the sensors numerically and with fairly slow updating.

If its EOBD compliant and you don't want to fork out for a Lexia, another option might be a Bluetooth OBD-II adaptor used with the "Torque Pro" Android app, if you have an Android phone or tablet. I don't know for sure if you will be able to graph the data with that but the app and adaptor together are only around £20 so maybe worth investigating if you have an Android device.

Bear in mind that even a Lexia is cheap compared to a new cat that is fitted when not needed!

[bamba]

I was just after some one to back my theory up really ,or say yes that happened to me and this is what fixed it,its always bit of a gamble unless you can see some thing broken in some way, Im not sure that the OBD II generic systems will give out graphical data,Until now i was put off buying lexia before due to compatibility issues with any thing other than windows xp, but now i see the latest versions support windows 7 & 8, so i'l see about getting it after this months fix is spent and out the way, and see if i can generate some work from it,just about every other car on the school run is a picasso.

[Mandrake]

Diagbox 7.xx and the Lexia app that comes bundled with it works fine with Windows 7 but only the 32 bit version of Windows 7. I've used it successfully on a Samsung NC110 netbook running Windows 7 professional 32 bit.

Some people haven't been able to get it to work on Windows 7 but without seeing their machines I suspect the problem is something other than the fact that its Windows 7.

[wheeler]

Does it have the secondary air pump like a 2.0L motor? These can seize up - it'll have a stored fault if so, not sure if it lights the orange dash alert.

There most likely will be an air injection pump on this car but all they do is get the cat up to operating temp faster when the engine is cold, the MOT emissions test should be done with the engine fully warm anyway.

[bamba]

Cat, removed, some damage seen on on side on the outlet, might cut the front off to see what the inlet looks like,and the o2 sensors came out without a fight, which is good.
possibly some signs of blowing at the cat/manifold joint ,which may have been the rattle ive heard for a while but never been able to trace, probably down to a worn engine mount.