MOT emissions fail

Dogtooth

Hello all, the car is a Daewoo Nexia, 1.5 16V, 1996. It failed its MOT last week. The results on the print out were.

fast idle

C0 0.762 fail
HC 95 pass
Lambda 1.017 pass

The natural idle test also failed on CO at 0.574 %

I thought it wasn't far off passing so I gave it a service, new oil, filter, plugs, air filter and a good Italian tune up and 25 miles drive, took it back for free retest. It failed again :eek:

CO 0.715 % fail
HC 98 pass
Lambda 1.022 pass

The natural idle also failed again on CO at 0.593 %

Last year it had a new cat and lambda sensor, any ideas please on what to look for?

Andy_Edinburgh

Do you know if the testing station allowed the engine to cool between you delivering the vehicle and the retest being performed? A few weeks ago I took advantage of a free council emissions test in a local supermarket carpark because my recent MOT emissions readings were uncharacteristically high (although it passed); the engine and exhaust were properly warmed up (I'd just got there on the way home from work), and lo-and-behold the readings were back to their usual low values.

The technician doing the test said they were seeing a lot of that these days, he reckons MOT stations are too busy (lazy?) to warm up the cars fully...

harveybobbles

Shove a can of treatment thru its fuel line and blast donw a motorway in 3rd...

harveybobbles

Andy_Edinburgh wrote: »

The technician doing the test said they were seeing a lot of that these days, he reckons MOT stations are too busy (lazy?) to warm up the cars fully...

I've known some places not to even bother doing an emmissions test!

MORPH3US

I fitted a cheap cat to my 99 Citroen Saxo recently and it nearly failed on emissions so i'm not sure if the two are related?

M

Dogtooth

The first test it had I did wonder if they hadn't warmed it up properly but this time it had a 25 mile motorway run and was driven quite hard. It was left idling right upto being hooked up to the tester so it was definitely hot. Harvey_bobbles I put a bottle of STP in on Friday. The CO hasn't really changed at all after doing all this.

anewman

New thermostat? Is it running cool?

mr_accountant

this site is useful, may give some ideas.

http://www.bobmckay.co.uk/emission.html

Conor_3

harveybobbles wrote: »

I've known some places not to even bother doing an emmissions test!

Sorry but that's rubbish. The computer won't allow an MOT test to be completed without the result sent from the emissions analyser - that's sent directly from the analyser, not typed in by the tester as that cannot be done anymore.

harveybobbles

Conor wrote: »

Sorry but that's rubbish. The computer won't allow an MOT test to be completed without the result sent from the emissions analyser - that's sent directly from the analyser, not typed in by the tester as that cannot be done anymore.

Get off yer highhorse - I meant from years ago, before it all went computery... :T

mrtoad_2

Clearly conor has no idea what he is talking about. The interface to send emissions data to the MOT computer was never adopted owing to the incompatabiltity of all the different gas analysers available to testing stations. Also there is no facility for entering the emissions data on to the computer, simply stating whether the CO, lambda or HC is either too high or low.
Another so called expert that obviously doesn't carry out MOT tests!!