Failed 02 emmisions - do i need to replace the cats

[Gelf VXR]

Monaro failed MOT for high CO >0.30% but lean lambda 1.04%.


I know some people say find a friendly MOT, I dont know one and today the test equipment is linked directly to the MOT server, you only get one shot, the garage is friendly allowing me to make several attempts to pass the test prior to logging on for acual test, its failing every time, saving me another MOT booking.

Since then I have repalced the pre cat O2 sensors and cleaned the airfilter, failed again high CO.

Next fitted new set of plugs, ran some cataclean, applied seal to joints between headers and cats, still failed CO and lean lambda.

Ive logged o2 voltages prior to the last trip to the garage, offside bank post cats are often lean when they shouldnt be suggesting a leak maybe in the cat itself, it has had a few scrapes being low to the ground. If Im not mistaken the post cats should read steady voltage somewhere around 650mv whilst in closed loop, mine are switching somewhat.

Before i take the plunge and get pair of new cats made, just looking for opinions and confirmation that the cats are shot, car does burn oil under load.

Edited by Gelf VXR on Monday 4th October 19:17

[robbyd]

mine failed one year on emissions - decided replace cats was first step - when we took the old ones out, they were just empty chambers! Nothing there at all. I'd say best place to start, and universal ones aren't too dear..

[stevieturbo]

Gelf VXR said:

Monaro failed MOT for high CO >0.30% but lean lambda 1.04%.


I know some people say find a friendly MOT, I dont know one and today the test equipment is linked directly to the MOT server, you only get one shot, the garage is friendly allowing me to make several attempts to pass the test prior to logging on for acual test, its failing every time, saving me another MOT booking.

Since then I have repalced the pre cat O2 sensors and cleaned the airfilter, failed again high CO.

Next fitted new set of plugs, ran some cataclean, applied seal to joints between headers and cats, still failed CO and lean lambda.

Ive logged o2 voltages prior to the last trip to the garage, offside bank post cats are often lean when they shouldnt be suggesting a leak maybe in the cat itself, it has had a few scrapes being low to the ground. If Im not mistaken the post cats should read steady voltage somewhere around 650mv whilst in closed loop, mine are switching somewhat.

Before i take the plunge and get pair of new cats made, just looking for opinions and confirmation that the cats are shot, car does burn oil under load.

Edited by Gelf VXR on Monday 4th October 19:17

What are the full test results ?

"high" CO....although not really high suggests a little rich.

The "high" Lambda suggests lean....again it's borderline to truly call it high though

So for most part I would say there is an air leak somewhere. If you could get a test result from each bank ( ie from the rear o2 port for a proper post cat test of each bank ) that would help pinpoint which side is causing the issue, or both.

[Gelf VXR]

Update, after getting a new set of cats fabricated from AAS, sailed thru emmisions

fast idle CO 0.01%
HC 30ppm
lambda 1.003



natural idle CO 0.07

Anyone wondering about there cat efficiency, nice log data attached for the new cat performance, see origonal post for expired cats.


%

[Lincsls1]

Thanks for the conclusion update.
Glad you sorted it.