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[frostbite]

Hey guys

Would a vehicle fail on high HC due to a bad cat and or fowled o2 sensor?

Could a high flow cat and new sensor pass an mot

[TheBoy]

I'd suggest over fuelling (check trims), or a badly worn engine.

[tunnie]

Did you drive it like you stole it on the way to the MOT? Mine failed emmisons, take keys, act like you stole it. Passed fine, burning testers hand at the same time 

[TheBoy]

Did you drive it like you stole it on the way to the MOT? Mine failed emmisons, take keys, act like you stole it. Passed fine, burning testers hand at the same time 

What did it fail on? CO could have been tired cat, and a hot cat can help there....

[biggriffin]

Try a new lambda, a bottle of cata-clean, then fill with shell nitro,Tesco 99,BP ultimate, then thrash the guts out off it.

[frostbite]

It failed the first fast test on though the roof HC.

Then on the second go the HC was high and just passed

I have a feeling they didnt let the car heat up for the test also it doesnt help the manifold is leaking either letting gas out or leting air in to fool the sensor

However when I drive the car in a normal sane way the exhaust has a certain sound

Then when I go for a spirited drive in sport kick down a few times then drive normal, the exhaust sounds deeper and is way hotter

[TheBoy]

it doesnt help the manifold is leaking

Well, there's a problem. Fix the faults you know about, as that will have an impact

[frostbite]

But when the manifold is red, its as if the studs are still whole although you can smell the spent fuel every so often

[Kevin Wood]

Can you post the whole printout, as seeing the readings that were within limits is just as important as knowing what it's failed on when deciding what the problem is likely to be.

However, a cracked exhaust manifold can introduce air into the exhaust and confuse the lambda sensor.

[omega2018]

i think the cats primarily reduce the co, not hc.  high hc is either excess petrol or oil being burnt, or petrol not being fully burnt.  could try changing the oil, if old it may have become contaminated with petrol or try a thicker oil that is less likely to enter the combustion chamber.  any blue smoke from the exhaust or oily film around the exhaust?

[frostbite]

You know what, Im an idiot its the Co thats high

The first run was 0.52% then second was 0.26%

It did puff blue once and the cloud stayed for ages. I have since fixed the breathing problem

Since fitting the ulter backbox a couple months ago its quite sooty already