Failed CO test

I picked up the Ghibli from the garage yesterday and found that it had not passed the Carbon Monoxide (CO) test.

I suspected it might not since it was pretty close last year too.

My car is categorised as E2, which apparently means that it must not emit more than 0.5% CO at 3000rpm (high idle). The guy who tested the car said it was emitting over 2% CO, over 4 times the legal level. I asked him if he thought it was the catalysts, but he suspected not. He thought the engine was not running smoothly and may just need a good shake down. He asked if I drove the car regularly and when I said no, he seemed to think that taking it for a long hard drive may help.

I suspect that the problem is with the fuel map.


If you look at the last dyno test above from Rica, you can see that at approximately 2600rpm the mixture suddenly becomes rich, with a Lambda value of about 0.84. In order for me to determine if the catalysts are the problem, I need to rule out this rich mixture as being the cause; running a rich mixture means that there's more likelihood of unburnt hydrocarbons leaving the cylinder (i.e. some of the fuel doesn't get burnt since there's not enough air in the mixture).

My intent therefore is to take the car back to Rica and ask them to remap the fuel, paying particular attention below 3500rpm to keep the Lambda value above 0.95.

If the CO is still bad after this, then I'll start to become a bit suspicious of the catalysts. The car is due a big service, so if it's still failing after this then I shall try the test with some known good catalysts and see how it gets on then.