Hi Guys
My frog failed it's MOT yesterday on Emissions and also a rotting rear subframe. Subframe I think I'm OK on and will be calling TCB for pricing in the new year.
For the Emissions, the garage said that the catalyst has failed and it looks like it's newer than the header, so might be an aftermarket smaller one. Earlier this year, I also knocked out the pre-cats.
My question is, should replacing the catalytic converter sort this and does anyone have any recommendations for a new cat?
Cheers
Tom
These work well:
https://www.cats2u.co.uk/3267-18 (https://www.cats2u.co.uk/3267-18)
This might not be practical, but a product like Cataclean can make a significant improvement. My partner's car has a 200 cell cat which has been on for several years. Her car failed & the testing station said 'new cat', - they didn't venture a cat-cleaner. Cataclean sorted it, - passed easily. You want to run the engine hard when you add it.
Change the subframe, make an MOT appt' & drive the car some miles before it.
Thanks both
Suspect it will be better in the long run to replace the cat. It's going to be off the road for a few months so can save up some pennies for a new one; also shiny new chrome pipes. I wonder if a previous owner replaced the cat with a non type approved one.
Cheers
Tom
As readings are not that far out. Could an exhaust leak be enough to cause the fail?
How much of a leak is needed to fail?
A good cat will read about .01 to .02, so reading close to .3 means it's at the upper limit and is close to end of life.
A leak anywhere on the exhaust can also give such CO readings. I had a TTE exhaust where the left tip fails, and the right tip passes and every year had to remind the MoT tester! Sure enough the only issue was how well the left tip was sealed to the back box.
The manifold to cat joint is a prime area for a bit of leaking - but that tends to also lead to an EML light with time (assuming a non-import with a post-cat sensor), so if no EML a leak is less likely unless it is post-sensor.
Mine had emission issues a year or 2 ago. Most here suggested the cat or maybe a leak somewhere. Despite no error codes, I replaced the 2 manifold O2 sensors and that sorted it.
Quote from: fawtytoo on March 16, 2026, 16:31Mine had emission issues a year or 2 ago. Most here suggested the cat or maybe a leak somewhere. Despite no error codes, I replaced the 2 manifold O2 sensors and that sorted it.
I've been wondering about this for a while. The o2 sensors as I understand are a serviceable item but are often not replaced as a matter of course. Although they may work and not throw a code, they can become sluggish or lazy.
I checked the resistance on mine at the weekend and got 13.4. Which sits nicely between the expected range of 11 to 16. But are they sluggish?
I accept that having dared touch them, I will be getting a code some time soon. :-\
Quote from: fawtytoo on March 16, 2026, 16:31Mine had emission issues a year or 2 ago. Most here suggested the cat or maybe a leak somewhere. Despite no error codes, I replaced the 2 manifold O2 sensors and that sorted it.
Can you recall how the emissions issue presented. Was it OK on one reading but not the other?
Was it just out, or way out?
Quote from: Ardent on March 18, 2026, 07:24Can you recall how the emissions issue presented. Was it OK on one reading but not the other?
Was it just out, or way out?
Subject to my memory (this was last year), it was way out with all readings up in the high red zone. The tester allowed the engine to idle for a while and it settled down, so he passed it, so I don't have any readings to show how high it was. After replacing the sensors, I asked for an emissions test and it passed correctly and stayed in the green.
EDIT: My MOT is due in the coming weeks so it'll be interesting if it's still ok.
Quote from: fawtytoo on March 18, 2026, 11:35EDIT: My MOT is due in the coming weeks so it'll be interesting if it's still ok.
I'd be interested to know the result.
I had an emissions failure on my Avensis (same 1zz engine), the garage couldn't find anything wrong, no exhaust leak, O2 sensors voltage and readings OK. I added a bottle of cataclean and went to the retest with the second gear almost redlining it. It passed straight away.