Running on 3 coils

[Areks_8]

Moderator: moved here as first post.

Hi guys!

Got the Rex as my first car in January, loved it. Had some doubts about my mpg and gearbox so decided to go to a garage to get the car checked over. Also asked for a compression test. Anyway, found out that compression was good, car was in really good nick but the previous owner fitted non-oem ignition coils which could cause issues (fitted about 3k miles ago). They said it could explain poor mpg. Then they went for a drive to check the gearbox out and came back saying bit of notchiness is normal but the bigger issue was that car was massively underpowered... That was a surprise to me as I had no complaints about the performance, just questionable mpg. Indeed, when I got in the car afterwards the difference was very noticeable, I just assumed something was disrupted when they did the compression test or perhaps the long-ish motorway journey just before made something go (don't drive it that much, normally pretty short drives) Anyway, they recommended new ignition system and cat. That was a few months ago, I kept putting the repair off due to other life stuff.

And yes, something was disrupted... opened the bonnet on a hunch this morning and found the 1st coil disconnected from the spark plug Could not believe it.. but also it explained it all. Feel silly for not thinking of checking that all those months. In essence I did 100-200 miles on 3 coils. After reconnecting the engine start was still a bit hesitant compared to being bang on before the garage. I assume the cat is f***d for sure now. The engine sounds healthy as ever and happily revs to 9k (tbf it did with 3 coils too...). Still feels kinda underpowered though.

Would it be a good idea to get some cataclean through it? Or just but new cat? Anything else you guys think might have been affected? I'm guessing new ignition is definitely a must now too.

[350matt]

Start with a set of new plugs and coils an possibly leads too
the ryan rotary coils are excellent and I've had a set on for the last 30K with no issues
https://www.ryanrotaryperformance.com/s ... mplete-kit
and plugs
https://www.ryanrotaryperformance.com/s ... k-plug-set

you can use one of those mini USB cameras from Ebay to lookk inside the cat if you remove the O2 sensor
and if the front of the brick is all deformed and melted then yep its had it

If its the original part the cat is is worth quite a lot to the Cataylst breakers ( up to 300 quid) , which is why our car is often targeted by the low-life cat theives
but this can then finance your repairs, just don't knock the contents out and then expect to sell it they won't want it as they need the part no of the OEM part

you can then fit a decat pipe for a bit ( until MOT time) to check all is well and then consider fitting a good quality aftermarket cat that will pass an MOT and give more performance too

[PaulAV]

It's worth checking the basics, air filter, MAF sensor, eccentric shaft sensor, make sure they are clean, the spark plug that wasn't firing may just be fouled, it would be worth checking. Also cataclean is worth a try, I use it as a service tool. If your need plugs jp4mance eBay shop is about the cheapest you will find for decent plugs, RRP coils are good but if they're out of your price range a few have used Hitachi coils from auto doc(wait until they have 36% discount, it does vary day by day)

[GreySilver Beast]

Hi & to the RX-8OC


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[Areks_8]

Hi everyone, thanks for the input.

So basically I'm looking to pay at least about £200ish for a decent coils? Is it worth replacing just the coils seeing that plugs were also replaced 3k miles ago (5 years no less). Should take the plugs out to check or maybe just test with an ohmmeter? I do want to avoid spending too much on it, but also want it to be right.

I just wonder if pre-garage my only problem was crappy coils and now it might be cat as well.. cause of the garage forgetting to connect the coil. Anyway got a bottle of cataclean so I'm gonna rip it on the motorway today! Hopefully that does something.

[PaulAV]

Swap the coils and check the plugs, don't be aggressive if you need to clean the plugs, use a solvent and a cocktail stick to agitate. It's doubtful the cat has suffered serious damage with one coil failed, but not impossible

[Shagrington]

Hi and Areks_8

[Areks_8]

Hi!

So I took it out for the cata-clean and all seemed good, pushed it all the way to the beep in 2nd and 3rd. Then gave it a bit of break, then when I tried to get the beep again in 2nd there was power loss above 7k RPM.. Other than that all ok, new coils are a must and see where we are I suppose. I took it out again later and no power loss in the high RPM (probably wasn't as hot though). Also I checked the cat during both these escapades (after stopping the car) and it wasn't glowing. Chances are the cat is OK?

[JeradRx8]

I'd say chances are the cat is okay, if you can get your hands on a set of coils and leads definitely do it. I just got the RRP mk3 kit with plugs, cost a lot but it's fit and forget, if you have degraded coils the difference is night and day!! If that's too expensive I'm not sure if the OE Mazda coils are any cheaper. You could have a chat with a used parts place like Boston Rotary, he may have a 2nd hand set of upgraded coils and leads for a bit of a saving.

If you are purchasing spark plugs make sure to purchase from a trusted source to avoid counterfeits and you'll be all good.

Always a good shout to get a compression test done if you haven't already, just let's you know where you stand so you have an idea of the health of the engine .

EDIT: I see you have already had a compression test, would you be able to post the results for us to see?

[350matt]

Other thing to consider is if the SSV solenoid is working as if it faulty this will limit top end power
as a quick fix swap it over with the air pump solenoid

rx8 vacuum system.jpg

[PaulAV]

Ssv tends to hit at 4,500 rpm then you get a boost at 6,500 when the apv opens, it's possible the apv is sticking intermittently, but first job should be make sure the basics are covered.

[Areks_8]

Comp results as of couple of hundreds miles ago:

Front:
-6.75
-6.35
-6.75
Rear:
-6.97
-7.12
-6.90

So pretty good for a stock engine at 50k miles. The only question mark is that imbalance on the front rotor I suppose.

I'm hoping that power loss at 7k RPM was just cataclean diluting the little fuel I had in the tank. New coils next week, maybe spark plugs too. Hopefully that will be end of it(does it ever end?)

[JeradRx8]

It will run fine on those numbers I'm sure. It probably won't be the end but it's a very important part sorted

[Clive]

Good to see you have a good healthy engine under the bonnet.

It is maybe worth knowing that whist the people above are happy with what they have fitted to their cars, not all RX-8 will happily accept non standard ignition coils because the cars ECU is seeing incorrect information.

We have sold Rotary Parts since before the RX-8 came out and will not and have never sold non standard RX-8 ignition coils for fear that even just one of our customers may suffer bad running issues due to a component we have sold them.

On the link below you will find all the ignition parts you will ever need, including a full ignition "health" kit that we sell to RX-8's all over the world to rejuvenate customers RX-8's

We hope this information may help.

https://www.racingbeateurope.com/mazda- ... -311-c.asp

[Areks_8]

Thanks for the info Clive.

And yeah Jerad, I got really lucky because I got it without a compression test. But it had a good price and good shell, plus it started hot no problem so took my chances!

So the plugs came off for inspection.. Not easy without taking the wheel off and no specific spark plug socket... Lo and behold the state of the disconnected leading spark plug:
https://ibb.co/PMNVBPv

The other ones were in a much better condition. All are NGK iridium and look fairly new (fitted 3k miles ago). So for the time being I gave them all a clean. The worst one got a needle file to it, making sure not to round off the edges that the spark likes to jump off. Went for a drive after and pretty sure gained a fair few horses. Still want replacement coils though.

[rx8hunter]

Further to Paul's post these are the coils I have fitted to my PZ: https://m.autodoc.co.uk/hitachi/8124216 (if you get the 37% discount via the app on the Monday they should be something like £43.41 each).

From the research I've done I'm pretty confident in saying Hitachi manufacture the Mazda coils - for example these are made in Japan and are the only aftermarket coil to use AIC-155 in the OEM number as per the Mazda coils.

[Clive]

Further to Paul's post these are the coils I have fitted to my PZ: https://m.autodoc.co.uk/hitachi/8124216 (if you get the 37% discount via the app on the Monday they should be something like £43.41 each).

From the research I've done I'm pretty confident in saying Hitachi manufacture the Mazda coils - for example these are made in Japan and are the only aftermarket coil to use AIC-155 in the OEM number as per the Mazda coils.

You have done better than me if this is correct information as I approached Mazda about the change in part numbers for coils when I asked about the failures earlier coils had caused .

They would only tell me that they had changed coil manufacture. So if your info is correct, were they making the earlier coils that failed or the later C coils that don't

[Areks_8]

Fast forward several months + a few thousand miles and as it got colder I started having issues on cold starts. Not holding idle, have to help it with some throttle. If I don't help it then revs drop right down and can get a misfire (only let it happen twice) alongside a very rumbly engine. No issues with warm start or driving in general. Getting decent mpg (I do mostly motorway).

Initially I replaced lambda sensor (had a CEL for slow response a couple of times) but that made no difference. Got a borescope in the hole and cat is in pieces/melted. Explains why exhaust is quite stinky at all times. Weird that I get decent mpg but I must be basically running a partial decat and that just messes with backpressure when it starts cold?

Tried to make it full decat for but those bolts would not budge so I'll be getting a high flow cat and a blowtorch and have another go or just give it to a garage to replace.

[qwakers]

buy a grinder and cut the bolts off..

but yes, the cat will be messing with the fuelling.

[warpc0il]

If the cat breaks up then large chunks can get jammed inside the catback, that are a nightmare to remove - been there, done that

[Areks_8]

buy a grinder and cut the bolts off..

but yes, the cat will be messing with the fuelling.

I can borrow one from work, can you get to all of them with a grinder though or you have to cut some things (on the cat pipe ha) on the way? I'd be doing all this with the car jacked up, might just give in and let the professionals do the work... Looked into a local rent a ramp but fully booked until February.

If the cat breaks up then large chunks can get jammed inside the catback, that are a nightmare to remove - been there, done that

What's the best way to approach it then, take catback off and shake it until you hit the jackpot? Fun times. I might give it some taps when car is running and see if anything rattles. Or employ the borescope again, probably no better way to check to be fair.
Re-read your message and I guess jammed means no rattling... so borescope time.

Also will the broken cat be worth anything to anybody you think? I saw somebody bought a used original rx8 cat with supposedly intact honeycomb on ebay for £40 ten days ago, what a bargain that was...

[*thomas*]

Not an answer to your question, but ATM, RX8 cats (oem from mazda) are insanely expensive (the last time I checked, they were asking 2600€ at German dealers).

The aftermarket (cheap) cats on ebay are not worth your money, so either you install a cheap decat (Japspeed?) or you buy an aftermarket from a decent source.

If it's legal, I would just decat the car. If the smells annoys you, your family or you just want to be eco-friendly, go for the previous option.

[Areks_8]

I know a friendly MOT guy, passing shouldn't be an issue. At the same time I daily the car so the smell could get annoying + probably not the best for the environment if it can be avoided.

With all that would it be a reasonable choice to get a cheap high flow cat from japspeed or the like? I struggle to see how it can be worse than the more expensive sports cats. Obviously getting OEM is out of the question, would be paying almost as much as the car is worth.

If I do get a sports cat I will still get emmissions checked out of curiosity, I'm guessing it could be an issue for someone when I sell the car (I'd probably sell it with a fresh friendly MOT).

[Cscameron]

The cheap cats can't deal with the heat the Rotary spits out so get torn up pretty quickly. Best option (I believe, I run a decat so not looked at it) is a high flow sports cat