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Discussion Starter · #1 ·
I’ve owned a 2012 Kuro Edition from new that has given me 10 years of trouble free pleasure. Recently it developed a misfire that gradually became worse to the point of the engine cutting out twice in a minute. I have changed the plugs and coil packs and it has ’almost’ cured the issue but there is still an occasional ‘lump’ when well warmed up. Can anyone shed any light on this? Ill add that it’s had the BBR 200 upgrade and the local Mazda garage think something they’ve done could be at play as they couldn’t find anything amiss but for a P0421error code. There are no dash warning lights illuminated.
 

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Banish a little rust a day people
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P0421 appears to be a cat efficiency related code, any issue with O2 sensors or fueling? Cat itself at fault, or now damaged due to previous misfire resulting in fouling of the cat?
 

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Discussion Starter · #5 ·
Of course Mazda will blame BBR, it's not something they can just swap like a plastic trim clip and then charge you through the nose for it.

Hows your fuel economy since almost fixing it?
Fuel economy seems to be fine as does the way it runs but for the occasional lump. Their diagnostic check threw up the P0421, but it’s not registering at all on my cheapo scanner. Prior to changing the plugs and coils, there was a P0300 code that has since disappeared.
 

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Discussion Starter · #7 ·
when does the lump happen, idle, under load, returning to idle etc
It doesn’t happen under hard load but more like when easing off the throttle. The car was returned to BBR on transport a few weeks ago regarding a loud engine ticking (a long story) and returned at considerable expense to me to be told there was nothing wrong with it and it was running perfectly. It was too, the ticking had, and has completely gone so even though they said they didn’t do anything to it, I think otherwise as within 2 miles of driving it, the misfire was horrendous and that’s when it stalled twice. Also, the car was returned with damage to the front wing (I have photographic proof it was ok when it went on the low loader but as BBR pointed out to me, I have no photos of it on it’s immediate return! The damage was bodged with white paint that was enough for me to miss it for a few days). It was then I changed the plugs and coils, but as of my original post, the lumping is still evident. As I am reluctant to let BBR anywhere near it again (total breakdown of trust), I took it to Mazda and that’s where I am now having spent over £1000 and still got a knackered car.
 

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You've totally put me off ever going to BBR, wow how shit! Can't trust anyone these days unless you supervise them completely.

The only suggestion I can perhaps offer if you're completely stuck is Mark Jeffries in Barry, Wales. I don't know that he can fix it, but he's trustworthy at least and will listen to you.

I'm afraid my only suggestion is as above. Take the car off and inspect inside.
 

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Banish a little rust a day people
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Yeh I've heard some pretty negative things about BBR, and their customer service.
 

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Discussion Starter · #10 ·
Yeh I've heard some pretty negative things about BBR, and their customer service.
Absolutely woeful! Once they have your money, you’re history to them which is ok for probably 99% of their customers who don’t have any need to go back to them, but for the rest like me, their customer service is disgraceful. I made a massive and expensive mistake ever taking my car there.
 

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Discussion Starter · #11 ·
Apparently the P0421 residual code is not an issue and is normal due to the catted manifold installed by BBR, so that’s a relief. This was confirmed by a local Mazda tech. However, having just returned from a 150 miles round trip over 4 days, the very occasional misfire/stutter is still there. It probably did it 6 maybe 8 times at the most, the worst instance (lasted about 5 seconds) occurring on my drive having just completed the 55 miles home. I had been sat at traffic lights literally 5 minutes earlier and it idled perfectly. I’m reasonably confident the car will continue to run ok in general, but I’m concerned about any possible long term damage due to driving with something lurking in the background so I want it sorting. My next step is injector cleaner but I doubt that will make any difference as the car is only ever fed on Shell V-Power. Any other suggestions or advice will be appreciated.
 
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