5 catalysts in 7 months

obi_waynne

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A3 1.4 TFSI 150 COD
I have a friend whos YSL MX5 car keeps eating catalysts.

Any suggestions on the problem will be gratefully received.

Mazda checked the car out and say it is running normally but it is clearly running rich. MPG is down, power is down and the cats keep failing!

Rather than replace parts at random it would be good to isolate the most common/likely parts first and try a fix in this order.

What ideas or suggestions do you have for diagnosing and fixing this?
 
A/F sensor. Or MAF sensor. Usually when these go the fuel will go up as it can't work out how much to put in. First thing i'd change is the MAF. Then a damn good service and go from there.
 
Get rid of it alltogether !! Very noticable increase in performance can be had by getting rid of the cat - I have a '93 Limited Edition which has been played with and loved lots - nearly breaks your neck on pull off sometimes and its a very naughty car as it just wants to go faster & faster.
Carol
 
Does it pass emissions though? Or do you have to put the cat back on each year for the test?

It does go to show how much these cats suck up in power terms on these though!
 
Don't need to put anything back on 'cos the engines are so nicely managed. Mine has straight through 4:1 pipes and low pressure air intake and has been 'played with' very nicely. No problems with MOT at all. For most basic and cheapest mods: Remove arbox & add intake, move timing up to 14', get rid of cat (meow!), put roof down & put foot on 'go' pedal = Mmmmmm :))
Carol
 
Most Cat failures are due to over fuelling, with the excess burning in the Cat and destroying it, this could be due to a faulty O2 sensor, faulty injectors, and if the engine has considerable mileage on it or has been abused, coolant may be entering the exhaust, also physical damage to the cat due to driving on rough roads(very common here in India)
 
Ok an update! The car has been fitted with a new catalyst, new lambda sensor and coil. There are new leads and plugs as well.

The car is now running better than it ever has before. Hopefully the problem has gone away.

Strangely it seemed to be running rich rather than lean looking at the state of the plugs :eek:
 
Ok an update! The car has been fitted with a new catalyst, new lambda sensor and coil. There are new leads and plugs as well.

The car is now running better than it ever has before. Hopefully the problem has gone away.

Strangely it seemed to be running rich rather than lean looking at the state of the plugs :eek:

Glad to note that the CAT burning problem has been sorted out, you say that it looks as if it is running rich, well, considering that the car has gone through 5 catalysts, it now seems as if your O2 sensor, and plugs / leads were definitely at fault,and there may have been some misfires earlier due to which the previous CATs got damaged , I say this because the CAT is not damaged by rich mixtures alone, because essentially there is no oxygen in the exhaust unless there is a misfire

Normally,with no oxygen in the e4xhaust, there is no catalyzed reaction and
with no reaction, there is no heat. Distinguish this condition from
misfires where there IS an ample supply of oxygen in the exhaust because
of the failure to fire one or more cylinders. Indeed, a cat-equipped
engine running on a dyno for an extended period of WOT time will not
heat the cat significantly hotter than the exhaust.
 

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