My sister in law has an old 1997 R Reg Vauxhall Corsa 1.0 engine (3 cylinder type) and it went through its MOT and keeps failing on emissions, so far we have replaced the Lambda sensor, The air flow metre, new spark plugs, New coil pack and new EGR valve and still it fails.

these are the readings from the test sheet...

1st fast idle test:

C.O 1.199% (Limit is 0.300%) FAIL

HC 237 PPM (Limit is 200) FAIL

Lambda 1.011 (Limit is 1.030) PASS

2nd Fast Idle test:

CO 0.571% (Max Limit is 0.300% FAIL

HC 183PPM (Max Limit is 200) PASS

Lambda 1.046 (Max Limit is 1.030) FAIL

Natural Idle Test:

0.415% (Max Limit is (0.500%) PASS

We are thinking of replacing the CAT but with the car being an 1997 R Reg feel if that doesn't do anything it will be a lot of money wasted, she is a bit upset as she hasn't been driving a year yet and its her first car we had a garage do a diagnostic test which indicated a problem with the air flow meter and the EGR valve but none of these have helped with the emissions.

The car has done 81,000 miles and the garage say it will be a full re-test fee of £54 now as logged it on to the VOSA computer to retest it without checking the emissions first. Any help or advice would be appreciated - Thanks.

In the first fast idle test it is running rich and the lambda is within limits, in the second it is running weaker with the HC in limits, a high lambda and a too high (though much reduced) CO

First off, using the second set of results and going the cheapest way, I'd be checking the exhaust system, particularly around the cat, lambda probe any part before the cat for a leak. Even the smallest leak, if it is in the right area will push the lambda reading up. If a car has been running rich for a long period it can reduce the effectiveness of the cat, it may be recoverable by getting it nice and hot for the test, or there may be some sort of fuel system cleaner that can be used. Other than that, I think that the cat is tired.

With regard to the fee, you only get one retest per full test, so if they do the restest according to the book, the restest is logged on before anything is checked and if it's wrong, it fails and the restest is used up. It'll need a full test next time.

Thanks, We are fitting a new cat on it on Wednesday so fingers crossed it will do the trick, She is a bit gutted that she has to pay the full fee again though.

what i've done in the past is go to a different garage and slipped them a tenner to chuck it on the emissions testing machine before going back for the proper retest... no help to you now i guess..

i'm liking fordfan's thinking.. exhuast leak before the lambda probe/cat, or possibly at the manifold

I went to my mates garage other day, bearing in mine my car passed its mot last month and put emmisions tester up exhaust and co and hc was fine but my lamba was off scale because i've changed exhaust after cat and its blowing very slightly on joint after cat,

I was quiet supprised how high it was especially as i had just arrived and engine was still warm,

You might also find a good thrash down motorway to get it nice and warm helps especially if the car has low miles on it

On the retest thing, that's why for anything that's measured, I'll do the measurements before logging it on. If the test centre books appointments and does not do a test on demand system, then it is permissable to use the MOT equipment for other than MOT tests in progress.

Thanks guys we will be taking it to a different garage and they have said they will test the emissions for her before logging it on for test this way we wont be using up £55 a time. Will keep you posted, and double check everything again.