How do you Poison a catalyst....

[FWDRacer]

Forget the obvious stuff like burning oil.

How far would emmissions need to have swung to permanently poison a catalyst. Would an intermitent misfire be sufficient and if so over how long a period (days/weeks/months).

Currently have a Ford Puma that flatly refusing to pass its Emissions test. CO is circa 3% and it won't hold Lambda in line with MOT requirements. HC are 100% spot on.

Any thoughts PH Massive?

[CNHSS1]

i had a misfire on a volvo company car which developed a misfire on the way back from germany and had buggered the cat by holland! dont think it needs much of a misfire and for many miles to cause an issue.

[That Daddy]

You have not poisioned it you have blown the centre out of it(if driven with misfire),when you develop a misfire you get unburnt fuel go into the exhaust then soon as its met with a healthy cylinders combustion it ignites the unburnt fuel in the cats matrix Boom! no more cat,just another thing to check when you get cat replaced make sure all of the bits of broken cat are removed from the silencer/pipework after cat unit.

[FWDRacer]

That Daddy.... I've not had any spontaneously combusting moments since I change the plugs and sorted out my at or on idle misfire problem. Certainly haven't blown the centre out of the existing CAT

[CNHSS1]

mine came out the exhaust in bits, looked like pummice stone or volcanic rock lol

[neiljohnson]

The cat may well be dead if you drove it for a long time with a misfire but even with no cat your car shoulds run lower co than 3%. Normally if lambda all over the place it points to a leak in the exhaust somewhere. In this case however it sounds like the lambda sensor has had it as these can also be wrecked by a misfire. Get a diagnostics check done anyone who has a machine can check the voltages from the lambda sensors (i believe you have 2 on yours one before and one after the cat althouh might just be one before it) and identify the problem. Failing finding anything there check the coolant temprature sensor as a false reading from this would cause the engine to effectlvly run on choke all the time (thinks engine is cold so runs rich) again this can be done with a diagnostic machine. Hope this helps.

[FWDRacer]

Cheers for the advice. Post 2000 Puma's run upstream and downstream Hego's... Unfortuntaly mine is a 97-R so only has an upstream Hego, and therefore no DTC triggered if the CAT has failed. The car goes on a diagnostic today and I think (hope) the Lambda is the culprit.

It hasn't got that charcacteristic tailpipe smell that comes with an FI car running on enrichment, but the temperature gauge has started to read erratically over the past month. Could it something as simple as a knackered T'stat?

Edited by FWDRacer on Thursday 28th June 09:28

[That Daddy]

FWDRacer said:

That Daddy.... I've not had any spontaneously combusting moments since I change the plugs and sorted out my at or on idle misfire problem. Certainly haven't blown the centre out of the existing CAT

Oh you wont hear it go,it suffers in silencethe only sure way to know is to check it properly,basically the cat just tightens up the co that little bit a healthy engine(just an example) can show about 0.4% (no cat)with the cat just pulling it down to the last 0.10%/0.20% for example.3% readings are not cat failure but something else,possibly Lambda probe/temp transmitter etc.

Edited by That Daddy on Thursday 28th June 10:15