My mom owns an 05 RX-8 that she bought used in 2008 with about 25K mi. on it. It currently has somewhere in the mid to high 30's. It's had no major issues, or really even minor ones since she purchased it. I'd never driven this model year before she purchased hers, but I did feel that the car idled rougher than it should, and didn't have as much power as it should from a stand still and under about 3K RPM since she bought it, and that's never really changed. It wasn't super bad, nothing that would indicate a major problem, it just didn't seem quite right.

Had a Mazda Mechanic take a look at it for a few mins last month when it was in the shop after someone backed into it in a parking lot. He said it was definitely idling rougher than normal, and suggested it could be the coils, but she'd have to bring it back in and he quoted like $130 to test the coils. Did some checking online, and that seemed to be a major recurring issue with these, and virtually everyone recommended replacing them between 20K-40Kmi. For $130 you can buy 4 new ones and do them yourself or pay minimal labor to install, so I shopped around and purchased 4 of them for her online. They just arrived a this week, but she hasn't had a chance to get them installed yet.

That brings us to today... She calls me from her work, and says that after she left the house, she stopped at a mailbox about 1/4 mile away and left the car idling as she put a letter in. I don't know the exact details and I wasn't there, so I'll describe the rest as best I can from memory and from her interpretation.

Apparently when she got back in the car and started to drive, the car started to sputter and stalled. She started it back up and tried to go again, but the car had very little power, and was apparently running rough and doing some sputtering I believe. Sometime within the first 1-3 minutes, though I don't know at exactly what point, she got a CEL. She said the CEL was only on for a minute or so then went out, but the car continued to be under powered. She continued to drive it gingerly, heading toward work, and apparently it was under powered for about 3 miles then went back to normal. Her work was only about 7 or 8 miles away so she drove it the rest of the way without issue, then called me when she got to work.

She's still at work, and it's 3PM on a Saturday, so options are very limited and she certainly can't do anything mechanically herself, especially not where she's at. If need be she could have it towed back home with AAA, and that would be the safest thing, but it might also be unnecessary and a hassle. She was already planning to have the coils changed out next week, so that will happen sooner than later now, but I don't know if that could be the issue or not. Without knowing much about rotary engines myself, off the cuff it sounded to me like it might have been some sediment in the gas (which she just got the day before, and only drove about 2 miles home afterward), or air in the lines, something to that effect (though I'm probably wrong). She got Super Unleaded, but the gas station she went to isn't one I'm fond of, and it's not a well known chain.

I obviously did some research before posting, and didn't really find any posts that completely matched up with her symptoms and issues. Lots of posts about sputtering or stalling that seemed to be fixed by new coils and/or plugs, so she'll probably have the plugs done too when she does the coils. 35Kmi. seems a little low for plugs to me, but it certainly wouldn't hurt or be a waste and perhaps with the RX8s it's not too low and she might be closer to 40K by now.

Obviously I have no codes to provide yet. The only place around and open today that could provide them would be a Pep Boys nearby, but I loathe that particular location. If she does take it there after work, and if there are any codes provided now that the CEL is off, I'll post them later. In the meantime, any help is appreciated. Thanks!

Oh, and she checks the engine oil very regularly and adds as needed, at least every 3-4 weeks, and she only drives about 100 miles per week on average.


** Edit/Update **

My mom opted to just have the work done at a shop nearby. As I mentioned, she already had the new coils that had arrived late last week coincidentally, so she had it towed to a shop about noon today and I asked them to replace the coils, plugs, and plug wires (she's more comfortable with me dealing with them). They had to call around to find and get the plugs and wires, and they won't actually have them until around 3-3:30 today. In the meantime they called me back about a half hour after it was dropped off, and told me that they'd actually seen the same problem in a couple other low mileage RX-8's, and he said it was from sludge buildup and would take about 2 hours of labor to clean it out, if the coils and plugs didn't fix the problem.

I was a little skeptical, since nobody that replied to me in the forum mentioned anything about sludge buildup somewhere causing similar problems, and I didn't even know where/what part(s) he was talking about, but he wasn't really pushing me to do it in lieu of the coils and plugs but rather afterward if the problem still existed. In my heart I really felt like it was the coils and I was just having the plugs and wires done for good measure and based on mileage, so I said we'll see where things stand once that's done and if the problem persists then we'll talk about the other work. Does anybody know what he's talking about with the sludge buildup, and how much truth is there to that causing similar problems if at all?

Anyway, they'd been working on the coils since shortly after the car was dropped off, and about 15 mins later he called back again and said that they finished the coils and the car started right up and was running great . I told him to still do the plugs and wires and those probably won't be done until the end of the day. In total it's going to cost about $300 in parts for the coils, plugs and wires, plus labor of probably about $150 for a total of around $450. All things considered it's worth every penny, and with the amount she drives her car she won't have to worry about these things for quite a while. I'm actually excited to test drive it when it's all done and see if it has the power from a dead stop that I've always felt it was missing, as well as to see how much smoother it runs at idle.

Thanks again for everybody's input, and she'll definitely be watching out for any of the usual symptoms that would indicated problems with the Cat.

 

Every indication there that it is just coils, wires, plugs. The only CEL that will clear itself without going through several additional drive cycles with it on is a misfire CEL. 35k is overdue for plugs, not "low". Many people here will preach replacing plugs more like every 15k, though 30k is at the higher end of acceptable. Some people replace them every 6 months, regardless of mileage.

No indication if it is an auto or manual. If it is manual, I'd recommend having her 'pop' the throttle more while stopped to keep it from stalling out till she gets it home and you can address the ignition issues. If she has an automatic, she can do the same thing if she shifts to neutral at each stop, but this can easily be a bit troublesome.

If she ends up getting stuck, just have it towed home, not to a shop. Towing it to a shop leaves you without many options, and if you already have the coils you can save yourself (or her) quite a bit of money in labor. It really is a simple replacement job.


Once the ignition is addressed, you should be aware that her cat is probably on it's way out too now (typical for running overdue on failing ignition). Watch it very closely for symptoms of hitting a "wall" of power loss, and monitor fuel mileage closely. If it starts suddenly dropping really fast, usually about the same time as high RPM power loss starts, your cat is clogging. Do NOT continue to drive in this condition, as you still start stressing the engine seals, localized heating can warp the engine housings, cook the O2 sensors, and if you really try to push it, light the bottom of the car on fire.

Dealers will want to do a diagnostics test via ODB2 to validate cat failure, but most clogs won't show a CEL anyway, and it can get tricky to convince them of the problem before you get to the critically damaging stages of failure.


Edit:
If the ignition replacement doesn't solve the problem, your money isn't wasted because it was needed anyway. Let us know that it didn't work, but the short list of items to move to are: clean E-shaft sensor, reset fuel trims, clean the MAF, validate/disprove a clogged cat, vacuum leak test, and finally engine compression test.

 

Thank you very much for the prompt and detailed reply. I drive a C5 Vette and the typical recommended spark plug change is between 50K-100K depending on which plugs you have. Most owners that I know changed the factory plugs around 60K. I changed my plugs and wires about 63K and can't say I noticed any real difference afterward, but my car has always run great. Anyway, that's what I was basing my "low" comment on at 35K, but we're not exactly comparing apples and apples here .

I've found a few different posts describing the process of replacing the coils, but do you happen to have a link to the best one that you can recommend for me to follow so I can try to do it for her? If not I'll just go with the best one I can find myself.

 

As RIWWP pointed out, it sounds like an ignition related issue.

Coils are simple to change. Testing them is also very easy. I would also recommend inspecting the spark plugs, as coils and plugs should be changed simultaneously.

This is just a side note, and most likely unrelated to your issue, but I'm also a bit concerned about the short weekly commutes. I don't know your mother's driving habits, but it's recommended (if not necessary!) to high rev the engine regularly, to clean out the engine and other ports. Also, short trips are not ideal for fuel mileage.
These are great excuses to take the car out more often and enjoy the thrill and handling of the RX8

 

Yeah, definitely not the same thing. Your vette probably has an average RPM of ~2,500 (over the life of the car), with each plug firing every other revolution, or 1,250 times per minute, or about 20.8 times per second, and a comparatively very clean burn. A Renesis plug is an incredibly dirty burn, lots of excess fuel to foul it, and is called on to fire 3 times per revolution, with an average RPM of 4,000, or 12,000 times per minute, 200 times per second.

VERY different environments.

Search:
https://www.google.com/search?source...il+replacement

Results:
https://www.rx8club.com/series-i-do-yourself-forum-73/diy-another-plugs-wires-coils-209818/
https://www.rx8club.com/series-i-do-yourself-forum-73/diy-how-replace-ignition-coils-168162/
https://www.rx8club.com/series-i-do-yourself-forum-73/diy-coil-packs-installation-tips-120475/

3 different DIYs telling basically the same thing

 

Thanks for the additional input. One thing I did learn early on when I was researching the car for her was that it was very healthy to high rev the engine, and she makes a point of doing that at least once every day that she drives it. Apparently this is an engine built for high rpms, and it's not a happy camper being driven regularly at just 3-5K RPMS. She has the auto btw, with the optional manual shift mode. As far as the plugs, I'll probably do the coils myself tomorrow and let her take it in early this week to do the plugs.

@RIWWP
Thanks for the links you provided, one or two of those are ones I'd already found, so I'll just pick one and go for it. Didn't think about the fact that the higher revving motor in turn equals more sparks per second, and and equally short life span. Makes perfect sense, and I'm sure the plugs are due for replacement given the mileage. I'll repost after the coils are done, and again after the plugs are done, with feedback on the results. Hopefully that's all it is.

One thing that concerns me a little is that the CEL light was on solid, and I believe from what I've read that the CEL light usually flashes when it's a misfiring as a result of failing/failed coils. In any event, the coils and plugs are due to be changed so that's the next logical step regardless.

 

Flashing CEL is random misfire, it can go solid from enough misfires, and then still clear itself.


The plugs are actually easier than the coils, and easily done at the same time. (right in through the driver's wheel well, nothing blocking them).

AdvanceAuto, Amazon, Mazmart, BHR, and several other sources have them for $20 each. Need 2 leading, 2 trailing. (marked on the plugs, and the corresponding T and L stamped on the housing next to the plug holes, and if that is still hazy, then T = Top and L = Lower )

 

Mazda's way of testing the coils is so retarded, basically its either work. Or completely dead. So the test is nothing but a waste of time

At ur miles. I would swap the coils first. But then u might want the cat look at because bad coils mean weak spark, which means more unburnt fuel, which kills cat.

Not that big of deal.

 

Again, thanks for everyone's input.

She got the car towed home, and I'm going to try and tackle the coils for her tomorrow. The car started right up and ran normal for a few to several seconds, then started to sputter and run very rough. That continued for several more seconds, then it went back to a normal idle again. I just let it do its thing for a minute or so, until at one point it eventually died. I was able to start it back up and pull it up and into the garage, but it was definitely very weak, and alternated between that sputtering state and running normally, but I didn't have any load on it. CEL has been on since she got off work and went to start the car.

I'm much more comfortable putting together a computer from a pile of parts sitting on the floor than working under the hood, but by all accounts it's a very simple job so I'd imagine I should be able to tackle it. Hopefully it doesn't require any special tools or extensions, as my toolbox is fairly limited.

Duly noted about that Cat btw, I'll have her watch for the symptoms I've seen mentioned here in the forums. To date I don't think those symptoms have appeared, so hopefully the coils haven't compounded the problem yet.