Mot

[lawser]

Ok, Just back from MOT with four failure points, 3, i can fix no probs...The 4th, exhaust emission fast idle test failure not too sure about.
On the 1st test CO: value actual was 0.490 % instead of 0.300 % - FAILED
LAMBDA: value actual was 1.029, has to be within 0.970 - 1.030, so just inside the acceptable tolerances - PASSED

On the 2nd test CO: value actual was 0.359 %, came down a little but still FAILED
LAMBDA: value actual was 1.073, so FAILED this time

Plugged in VCDS Lite & came up with no fault codes whatsoever.......

I don't think there can be much wrong, any ideas folks ?

[fourringsrus]

A cat failing?

[zollaf]

what engine are we on about, and what year ?

[scotty33]

You can test the lambda sensors with a digital multimeter:

http://www.12v.org/maintenance/repairs/o2sens.php

May be worth checking the coolant temp sender for the ECU?:

http://www.12v.org/maintenance/repairs/ect.php

Both items can be out of spec but not 'failed' so would not show a fault code

[lawser]

Thanks guys, previous owner put new exhaust system on in Jan 2009, @ £520 i would hope the cat hadn't failed already
I will test the sensors tonight....Thanks.
Going back to the emissions would it be worth adding some sort of fuel additive before puting through the test again ?
It's an 1995, ABC 2.6, V6 auto, engine,

cheers,

[fourringsrus]

Are you sure the £520 included a new cat though, I was quoted £500 for a system without a cat last summer, also '95 abc v6
As it turned out I only needed a cat and found a nearly new one on a wreck,£40 lovely' and though my car is not running at it's best, it passed the mot clear just 2 weeks ago

Stuart

[zollaf]

i would give it a dose of forte petrol treatment, then drive it like you stole it for at least 10 miles, then get it retested while it is still nice and hot. if that doesnt do the trick, and there are no fault codes logged, and the airfilter, plugs and oil are all new, then it may well be the cat. as stuart has said, the exhaust may not have included a new cat, or it might be a sports cat that doesnt work very well.

[lawser]

Point taken....Just assumed that it would have been a complete exhaust system for that price
I've gone down the route of treating the petrol & giving her a thrash before the MOT, recommended by a few folk....

[lawser]

Thanks folks....Passed the MOT no problem now

[fourringsrus]

Well done, it's a weight off your mind when they clear these hurdles