I’m looking for technical help or recommendations on: replacement catalytic converter
We fell victim to the dreaded Cat thieves recently and bought a complete replacement system including stainless Cat which was recommended by someone on this forum.
All appeared okay until the engine management light came on with the P0420 fault code which, like the proverbial bad penny keeps coming back.
I have been offered a refund or replacement as well as the option of upgrading to one from a different manufacturer at additional cost.
The problem is, how will I know if I am going to pay for fitment of another Cat and not be in the same boat as before?
So, does anyone know of a MANUFACTURER of aftermarket Cats which don’t trigger the P0420 fault code as well as passing the required MOT emissions test?
Does such a thing exist or is it a mythical beast?
I’m not prepared to just live with the EM light being on, in case another fault occurs and is ignored.
Like others on here, we have been told that the vehicle would be written off if we claimed on the insurance so we are not going to go down that route, nor are we prepared to fork out for a new OEM one.
Thanks in advance for any suggestions.
Paul
That is a sorry story and reading the post I thought this might be me that supplied. This is the way my day is going:-)
If it is, I can only say that I have had an aftermarket cat on my MK1 since 2004 and still gets the car through MOTs. The one you purchased would have been type approved?, so even less chance of a problem.
Who did you buy from and what are the part details please. Has the vehicle got any history of emissions issues(MOT history)
The VVT engine is usually good on emissions and no issue with an aftermarket cat. P0420 is a generic error code…
What causes the P0420 code?
Damaged muffler or leaks in the muffler
Damaged exhaust manifold or leaks in the exhaust manifold
Oxygen sensor wiring that is not properly connected
Damaged oxygen sensor connectors
A fuel injector that is leaking
Fuel pressure that is high
Use of the wrong kind of fuel (using leaded fuel instead of unleaded fuel)
A number of other possible reasons for this you may want to investigate.
Cat failure should be detected by the post cat sensor and produce a much more useful and less generic error code but don’t ask me what it is; look it up and report back please
Thank you Rhino, the Cat was sold as type approved (Euro 3), certainly it has passed an emission test at my local MOT station, though initially it showed red when a leak was detected in one of the joints. With that rectified, it passed.
The Cat was bought from Cats2U, who I must say have been excellent so far with their after-sales communication.
The reference on the invoice says: MA6073T MAZDA MX5 1.8 11/00-10/05 and the one they are suggesting, should I want to upgrade is on this link:
I should point out that Cats2U are not suggesting that the alternative Cat will perform any better, only that sometimes changing the Cat to another brand resolves the P0420 issue.
In answer to your questions, the car has never had any previous emissions issues, and we have owned it since new.
Something that the guy at Cats2U highlighted on the recent emission test are the Fast Idle readings which seem a bit high apparently, indicating a possible problem, they are:
CO 0.02 %vol, HC 40 ppm and Lambda 1.03, the natural idle CO was 0.03 %vol.
When the car passed its MOT last June the readings were: CO 0.03, HC 21, Lambda 1.00.
So it does seem like the HC reading has shot up significantly, though apparently still legal.
Could this be responsible for the P0420 code?
All the sensors were left intact on the parts of the exhaust system not stolen, so were just plugged into the new pipework and as far as I know the car is otherwise untouched and running well, though the replacement mid section and back box make the car a bit louder and there is a smell of exhaust or fuel on startup from cold which seems to disappear once running.
None of the fuel lines have been touched, and the car has always been run on unleaded or more recently Super Unleaded.
I have retained the original back box which I plan to have refitted once the Cat issue - if indeed that is what it is - is sorted as it is still perfectly serviceable after 19 years and is nice and quiet.
I just wish the darned EM light would go out and stay out!
I would welcome any further comments you may have and again thank you for your response, it’s much appreciated.
Paul
The second cat CATS2U suggest is the one I sell and the manufacturer is one I have dealt with for nearly 20 years. Price with delivery is almost exactly what I charge.
The cat you fitted is a cheaper aftermarket part made by EEC. I feel I should knock it, like I would an MX5parts cat but can’t in all honesty come up with a reason why. Looks like it has a 2 year guarantee which is as good as it gets with aftermarket cats.
your car does not appear to be running right. HHC(hydrocarbon) of 41 is too high really, 21 is fine; pass is 200ppm but figure should be about 20. HHC is soot; cats don’t like soot and a warrantee claim would not be entertained at 60ppm or above. The irony here is the lambda reading at 103 which indicates a lean fuel reading. Still right on a pass but not acceptable; there is a problem. CO always seems to be the struggle at MOT time as more realistic MOT expectation.
I am sure that the issue is covered somewhere within the P0420 list of reasons but hard work to analyse without another code to pinpoint the problem. I’m going to say that the CO reading really lets the cat, cheap aftermarket or not off the hook in my opinion.
Hi Rob,
Thank you once more for your guidance.
From what you say it would appear I have a problem which may not be related to the Cat.
I guess that I should get that investigated before I decide whether or not to replace it.
If we take it that last June’s emission readings were about right, the first thing to check is whether the leak is indeed fixed properly - the mechanic reported that it was very difficult to get a seal due to an alignment problem with the MX-5 Parts exhaust system and new Cat.
Failing that, I’m presuming the engine’s own management system should sort the mixture out so it’s difficult to see what else could cause the high HHC readings and it sounds from the Lambda reading like it is doing its best to compensate.
You mention ‘another code to pinpoint the problem’ is there somewhere I could take the car that might have a more sophisticated analytic system that might help focus the search?
I’ll ask my mechanic to work through your list to try and eliminate anything else in the meantime, but it’s all expense and hassle when three weeks ago we didn’t have a problem - and now all of this!
Once again, your advice is much appreciated.
Kind regards
Paul
I think the P0420 is being generated by the comparative readings from the precat lambda sensor and the post cat lambda sensor. If that is the only code stored, then that is the situation. No kit, however sophisticated will pick up another code as not there.
Given the lean lambda reading read from the exhaust, I am thinking exhaust leak.
If that occurs after the precat lambda but before the postcat lambda, would make perfect sense. A leak before the precat lambda, usually in the manifold on these cars would upset fuel/air for engine running. It appears that your engine is running fine.
HC is high but not massively so and if the cat were failing/failed I would expect a much higher CO reading.
Your theory of a poor seal between cat and catback gets my vote.
Thank you Rob, I will have our mechanic check for leaks again in the first instance.
If he still has a problem I may go for the upmarket Cat and get the original back box refitted in the hope of a better chance of a proper seal.
I think that’s about all I can do provided all the fuelling side of things is okay.
With luck, the P0420 code will be satisfied.
I’ll let you know how I get on.
Much obliged as ever.
Paul
I can’t help at all but I feel your pain with that EM light keep coming back!! My local garage have replaced both oxygen sensors after getting the P0420 code and after a couple of short journeys that light just comes back on. They’ve suggested replacing the cat but I’m not keen to fork out for that in case it’s not the problem! Car running fine so tempted to ignore it but know that’s not an option!
Hi folks,
I thought I’d update you on the ongoing saga of the replacement Cat for our '04 Euphonic.
Everything checked out engine-wise and yet the EM light refuses to go out and simply returns after every reset.
I have been dealing with the supplier Cats2U who I must say have been very sympathetic and proactive in helping us to sort the problem.
On their advice and with the confidence of a 2-year refund warranty I ordered another Cat through them in the hope that may solve the P0420 issue.
The first cat (Cat1) manufactured by Euro Cats was not an easy fit, but it went on, the replacement from BM Cats (Cat2) wouldn’t even come close to fitting, there not being sufficient room between the two downpipes to allow any wiggle-room to get the bracket to align with the bolt holes on the side of the gearbox. For some reason they use larger diameter tube for the downpipes which hampers things as well as inconsistent gaps to make it even harder.
I sent video and photographic evidence to Cats2U who forwarded it on my behalf to BM highlighting the problem and BM said they would send another (Cat3) which they said they would check before despatch that it met the specifications of their original (Mazda) item or drawing thereof.
Cat3 arrived yesterday and the gap between the pipes was virtually non-existent.
This suggests that (1) the notion they may actually take the time to examine it was BS and (2) there are significant inconsistencies in their manufacturing process, they can’t even get it consistently wrong.
The car has now been taking up space at the garage for all of this week and we are still no nearer reaching a situation where the car is usable other than to replace Cat1 and live with the EM light.
The interesting thing is that apparently 700 of these aftermarket Cats have been sold in the UK and allegedly we are the first to raise an issue of the fitment of the bracket between Cat and gearbox housing.
So how is it that all the other 700 managed to fit without difficulty?
Are there any of those 700 on this forum?
This whole thing has been an utter nightmare and heaven knows what the ultimate financial cost will be, just to have to live with a constant reminder of the Oik that stole our original Cat in the form of a glowing EM light forever more.
This is hopefully a conclusion message to a pretty drawn-out affair following the Cat on our '04 Euphonic being stolen in February.
There is information in here that might help anyone in a similar situation avoid some hassle.
We initially bought a EuroCats replacement from Cats2U which proved unsuitable due to it setting off the EM light as detailed previously on this post.
On the advice of Cats2U we opted for a slightly more expensive one manufactured by BM Catalytic Converters in the Midlands.
This had no problems with the EM light issue, but the twin header pipes as supplied didn’t allow for the bracket that bolts it to the bell housing to be fitted and I raised this with Cats2U the supplier.
The next day a replacement arrived, but you couldn’t fit the proverbial ■■■ paper between the pipes on this one so I called Gary at Cats2U who immediately contacted BMs to raise the issue.
As a result of pressure from Gary at Cats2U, BM procured an OEM secondhand part and used that to re-manufacture one to the exacting standards of the original and that has since fitted like a glove without (so far) any issues whatsoever using the standard bracket attaching it to the gearbox.
My understanding is that BM have revised their jigs to manufacture systems to the same measurements as the OEM part.
It has been a bit of a saga to be honest, but we got there in the end.
My advice to anyone unfortunate enough to suffer a Cat theft is to pay the few quid extra for a BM replacement, which, with their revised manufacturing process in place, should now fit without issue.
Lastly, I cannot recommend highly enough Cats2U, they really were on my case throughout and weren’t happy until I was completely satisfied.
I hope this helps.
Paul D
I think it is, Roger. We have had no further issues and the car went through the MOT emissions test with a better figure than the old, standard Cat.
No sign of any warning lights either, so I would recommend the BM Cat and particularly Cats2U for their excellent service through a difficult episode.
Hopefully, anyone buying one now will get one that fits as it should and perform like the standard item.
Hi
I have a similar problem on my Mk2 2003. The engine light keeps coming on and they’ve narrowed it down to the oxygen sensor on the catalytic converter. The car drives fine but I’m limiting my mileage until it goes to the garage. Is it safe to drive while I’m waiting? I’ve got another two weeks before it goes in.
I have to say, your responses to @Duffspeed have been thorough in the extreme. Although I rarely post anything on here I’ve found the whole MX5 community to be nothing other than engaging and helpful. Your responses on here have epitomised that. Thank you.
My apologies, I rarely visit nowadays.
The precat lambda controls fuel/air, so a faulty sensor will potentially cause issues and damage.
I guess this is academic after 18 days but please get back to me.
I don’t get on here very often either but thank you for your response. It’s much appreciated.
I had both sensors replaced and the engine light came on again so they’re going to check the sensor wiring and the rest of the exhaust. It’s booked in again tomorrow.