In August 2008 I fitted a Larini back box to my MK3 Sport 2.0L.
On a number of occasions since fitting the exhaust the engine management warning light on my car has come on. On the 1st occasion the dealers simply reset the system. On the 2nd they replaced some of the senders. On the 3rd (early December) they replaced the catalytic converter and on New Years Eve the light came on again.
The agent (Perry’s in Blackburn) have today removed the Larini box and put back the original Mazda box and I will now wait to see if that has cured the problem.
They say that the indications from the cars management system are back pressure (or lack of it) in the exhaust.
Apart from lowered suspension there are no other modifications.
Have any other members experienced this problem?
Regards
Jim
Moved topic to ‘Engine’ due to content.
Do you know which fault code is stored when the light comes on?
The fault code is P0421 - PCM warm up CATsystem efficiency below threshhold.
The CAT was replaced under warranty on previous visit.
Regards
Jim
If both the oxygen sensors have been checked/replaced and the catalyst also replaced then there is some logic in refitting the original rear box it certainaly needs changing to rule it out if nothing more. There are no leaks in the exhaust system are there?
That DTC is generated by the PCM by monitoring the out put from the two O2 sensors (one before the cat & one after) to check the cat is working. There shoud be a different output from each sensor when the cat is working.
Assuming there are no other faults with the engine managment system (no other codes stored) then the dealer seems to be on the right track. After ruling out the exhaust if everything else IS ok, it pretty much only leaves a fault with the PCM! But that is extremely rare!
Sorry I can’t offer any positive help at this stage. Please keep me informed of the progress.
Hi,
I’m just curious what happened in this case, did it get solved and if so what was the problem?
Cheers
Drew
Hi
Mazda specialist has been on the case for some months now. He is based in Dartford, so it’s a long trip to Blackburn to inspect.
He went back to basics with replacment transmitters (came on again), 2nd replacement cat (came on again) and recently instructed them to replace the manifold. That was about 400 miles ago and light is still off. Will have to wait quite a bit longer as light was once off for nearly 1000 miles. No suggestion that the Larini has any bearing on the matter. Car now up to 34000 so the problem has been there quite some time.
Regards
Jim
Just out of interest, who is the Mazda Specialist in Dartford?
I think MadJim is refering to a field engineer from Mazda head office which is in Dartford.
It is now 2 months since the new manifold was fitted and the car is now showing 35,500 miles on the clock. I am cautiously optimistic that this has solved the problem as the light has not come on again.
Regards
Jim
Am rather interested in fitting a Larini to my mk3, did you put it back on in the end- and did the light come back on with the larini fitted?
Sorry to hear of your problems Jim. I (eventually) replaced the whole system with a Larini. First changed was the rear box but no change in noise or peformance. Then changed the rest with mid pipe and sport cat from Larini so I now have a Larini system from the header back. No engine lights problems, better performance and nice sound. Cost almost £1000 though.
Was there no change in sound just from the backbox? My friend’s Mk2 sounds much much nicer with just the larini backbox, is it different for the mk3?
Ah well, there lies problem. I have an extensive post on MX5com site, http://www.mx-5.com/Forum/Room/Topic/?topicId=12444 regarding Larini and exhaust notes. Friend of mine has a mk2.5 and his sounds glorious. Ordered mine for the RC and just rear box sounded very slightly different to that of stock box. Larini said the best system they did for the MX5 was for the mk2 and 2.5. I f you have a mk3, suggest you click the link and have a read.
Did it mature over time in the end with the full system? Have you had a chance to compare it to other people with just the backbox- did you get a dodgy one or something?
It is sounding better with time, remembering I now have a full system fom the header back, and it breathes better now so some increase of response through the gears. That said my friends Larini is well “sooted”, been on his car for over 2 years and mine is a long way from that, but pleased with final result. Just a tad expensive.
I’m not sure if they still do the full system, but as I just spent 10k on the car itself, a whole 1k on an exhaust for it is a bit much! I might have to try just the backbox first and then if it doesn’t mature see if I can get them to make up the middle/sports cat or fit one from another system.
The new manifold appears to have fixed the problem as it is now about 8 months and 8000 miles with no warning light.
I have just the Larini back box and am very pleased with the sound and would reccomend to anyone - but I believe Larini are no longer making them for MX5’s and just selling existing stocks.
If Phil reads this, I did try sending a private reply using the link provided in your private message but got “Topic closed” message.
Have a friend in the club with a MK3 with Larini back box and he reckons it is the best exhaust note he has had on a MX5 over 15 years ownership.
Regards
Jim
Thanks for all the help guys, I’ve rung up Dave (I think) at Larini and he’s got some left, think I’m going to give it a go, if it is the case that it doesn’t sound as good as anticipated then I’m sure it should be easy to sell on if they aren’t making them any more, just selling existing stock.
Or maybe I can get a straight-pipe custom made onto it with a sports cat- that might add to the larini tone.