Ax failed MOT on emissions

[Jaf]

Hi guys. It's an 1994 1.1 petrol car, my dad's. Actually we're in Spain but the emissions test is the same. It's the only failure. The ecu light comes on a lot, battery earth off solved it for half hour. Dad was told to check the throttle body as advised here 2 years ago!! Car drives same with ecu light on or off. Obviously light was off during emissions test. Going to plug in Lexia, look at spark plugs, filters, throttle body. Any advice please? Thanks.

Tickover co 2.13%
Rev test co 0.83%
Lambda 1.017

Last year passed fine with,
Tickover co 0.35%
Rev test co 0.07%
Lambda 1.022

[xantia_v6]

I would say that the indications are that the catalytic converter has died. The lambda value is OK which usually means that the mixture is OK and the engine running OK, but the CO figures are more or less what you would get from a car with no cat fitted.

Sometimes, particularly in winter, the problem is that the catalytic converter has not warmed up properly when tested, a sympathetic tester will rev the hell out of the engine for a couple of minutes, or take the car for a spirited run before running the test again.

[Jaf]

Thank you. I'll admit that when I saw the co was 2% I thought why would they fail that...as my cars have always been the older ones allowed up to 4.5%. Oops. *Goes away to read about cats*

[Hell Razor5543]

When I took my C5 out for her MoT last time I took her for a nice blast along the motorway first. She only needed one go on the emissions rig.

[Jaf]

Quickly plugged in the Lexia. It showed Permanent Fault, Mixture. Cleared it and the car seemed to run cleaner. Got dark! Going to plug in my old CO tester tomorrow and have a good look at things. Will be looking to see if CO goes down after a hard drive. Although the drive to MOT place is 50kms it was snowing so drove slower and engine was not hot hot.

[Jaf]

Ok so the weather's been horrible, not getting very far.

Plugged in CO tester, with cold engine the CO was 10%. Took the car for a 15min hard drive, couldn't see any visible smoke. Tested CO, went down to 0.2%, perfect. Drove home which is downhill so the car was not as hot, though the fan came on, tested CO again, gone up to 2.1%.

On the way home the Check Engine came back on. Still Permanent Fault Mixture Adjustment. Made no difference whether the fault was showing or not to the CO at tickover with warm engine.

Does this make sense that the Cat is at fault? Will a faulty cat cause the Check Engine light to come on?

Thank you.

[Jaf]

Ok so plugged in Lexia again. Something is wrong!

Very strangely the car seems to be set up to run best with the Engine light on. Runs at 900rpm and CO goes down to 0.2, Idle actuator is 14 to 24%. With Engine light off runs at 700rpm and CO goes way up to at least 2 (6 or 10 when engine cold), Idle actuator is 80%.

Any ideas? Thanks.