Check the little air hose under the throttle body is still in place and not damaged - an air leak there will cause that misfire, and is fairly common.....

If my car was doing this, I'd be inspecting the spark plugs and cleaning them right away. What you are describing is not normal running behavior.

Bloody Hell, that is NORMAL!!

Just to Qualify, unless you want to change your spark plugs much earlier than "normal"...

ASK yourself this question, IS your car missing under load????...no.? well ALL is OK.

The odd FLUFF, PUFF or Miss at Idle is NORMAL....

yea, its just the characteristic of a rotary engine.

ASH8, I don't understand what you're referring to here. In post #20 you say your car idles smooth as silk once it's warmed up, now this post suggests it's normal to miss occasionally.

In 25,000 miles my 2009 has only rarely done this when first started in very cold weather OR if it hasn't been opened up and redlined in a while. Other than that, 99% of the time it idles as smooth as any other car without any puffs or misses. Before I decided to buy new, I test-drove a lot of series-I cars, and never noticed any odd misses at idle on those either.

That's why I don't regard this as "normal" for a warm engine idle, which was the OP's stated issue ....

Oh Jesus. I am not going to MICRO explain EVERYTHING I fucking say, Yes my car is SMOOTH AS SILK, with the ODD fluff and Puff at Idle, whether is is HOT or Cold, at stone COLD your CAR does not IDLE does it!?, think about that one..

99% of the time..you say, so what happens with the other 1%?????

It is NORMAL for a ROTARY...ANY ROTARY...particularly with some miles on plugs...Now do you want to go into HOW MANY miles...how you drive, what RPM, what Gas.

Did you actually HEAR the Vid?, what about the one above it??

I repeat what I say, IF the car is not Missing Under LOAD there is Nothing WRONG!

I say take out the plugs and inspect them. If they look pretty bad, change them.

It sounds like the car was purchased used? Used cars (and some new cars that sit at the dealer too long) get started a lot, run for a little, shut down, moved over and over and over again until someone decides to purchase it. This leads to spark plug issues and misfires (which will also cause premature wear of your cat).....

My 2009 sat on the lot for over a year, probably started and idled and moved quite a lot in its lifetime. I pulled the plugs at like 3000 miles just to make sure. They still looked ok at that time. But I plan to change them out at 10,000 miles.

Mazda used to have the dealers install new spark plugs just to combat these kind of issues before a customer took delivery of their new RX-8 but stopped the practice. The spark plug set was in the glovebox.

Interesting point. I bought a new 2009 model at the end of the year (12/2009). It has been exhibiting the puff/popping behavior both during warm-up and at idle after a highway drive. I always thought it was normal - but then again the dealer did replace my cat at 6,000 miles after it threw a code.... Possible connection? Maybe... maybe not...

I already explained, the other "1%" is when the motor hasn't been opened up for a while.

I was only seeking clarity about the information posted - don't know why that deserves an expletive laden tantrum.

:slap:

I've had similar rough idle issues, thought maybe the spark plugs needed changing or something, but then i noticed that when the clutch is fully in, that there is no rough idle, thought that was interesting, then I got a Recall/warranty extension program from Mazda saying:

On certain 2004-2009 rx8 vehicles, it is possible that the clutch pedal bracket may have a crack, causing an abnormal noise. If the clutch pedal continues to be operated with this condition, the clutch pedal bracket may break, changing the disengagement point of the clutch and possibly preventing the shifting of gears.
-kind of vague
..then they go on to say they will replace if free of charge

Is it possible that the broken clutch bracket causes the rough idle??
about to check that out at the dealer

As others have said it's mostly rotary related however, it gets worst with faulty plugs and a weak ignition system. Don't let the low mileage fool you. Rotary plugs can wet foul sooner than later (especially in cold climates). The engine tune will increase fuel delivery the colder the air temps. More fuel with weak ignition system equals plug fouling sooner than later. That I can guarantee you. Regardless if the S2's are not having coil problems, I would upgrade them. With rotarys you want the strongest spark possible for all situations. Helps fight carbon build-up as well.

I'm having the dealer inspect the car today (later this afternoon). With this few miles, I'll route it through them before I wander off and do my own work on the car. It's not that I'm not capable of doing the work, I just want them to have it in their records, should anything happen down the road. With as long as the warranty time is on the engine, I'm going to leverage the dealer much more aggressively for stuff like this.

My guess is that it's fouled plugs, and that there's something about the S1 and S2 engines that makes them more likely to miss than the RX-7s did (I have a friend who currently owns one of every generation RX-7 and an S1 RX-8. Only his 8 misses, just like mine does. Our car sat for a couple months at two different dealers before we bought it. I'd be surprised if it wasn't flooded during that time, too. Tons of quick starts, moving around on the lot, and shut back down when cold.

But, we take it to the dealer for now, let them replace the plugs, and get it down that we "take good care of the car" in their computers.

Now, the car is fully opened up every time *I* drive it. My wife is much less likely to go WOT and hold it to redline. I don't have any compunction with doing so. I'll gladly run the engine hot and hard, but it's never NOT missed when hot (or cold, but I give engines a lot more leeway when they're warming up).

Update after talking with dealer
 

To diagnose, they need to keep the car for a day or two. At a minimum, it's getting a compression test.

Which tells me that Mazda USA is REALLY paranoid about these engines, even the S2's.

Does anyone have a US/Canada Factory Service Manual that can look up what the diagnostic procedure is for a misfire? I'm guessing there's TSBs or other dealer notifications that would supersede the FSM's diagnostics procedure, but I'm curious what it says.

Anyway, it goes back tomorrow (when I can arrange a ride home). Guess I'll be driving the 350Z instead. It's for sale, and I've been keeping it garaged to keep it clean.

gosh, guess someone just not suited to own a rotary.
mine pops no matter what. usually 3-5 seconds interval, more frequently when cold. just love it.
tho warm pops and cold pops are totally different.
warm pops are quicker and less car shaking, and usually happens at idle. the cold pops I can feel the whole car shaking.

You can say that again! Jason!...

There are NO TSB's for "this non Issue"

Sounds like the car needs a GOOD Thrashing, that is what Dealers do here

Just did my plugs.

2009 at 10,130 miles. I take it to redline at least once a week.
The leadings are on the right. I probably will continue changing the leadings every 10-15k and the trailings every other time.

https://www.rx8club.com/attachment.p...1&d=1297833286

Trust me, that's NOT the problem. It gets plenty of high-rev, high-load driving.

And, since I have friends that have owned rotaries for years (multiple of them), and they've confirmed that the RX-7s DON'T do this, it's something peculiar to the RX-8.

I'm very willing to let the dealer poke around at it, and if they can't fix it, then I'll go look into other solutions.

This isn't "a rotary thing". It might be an RX-8 thing, but not a rotary thing. Too many smooth running, smooth idling rotaries (in RX-7s) exist for it to just be an issue with having a rotor instead of pistons.

Now THAT looks like a problem, and if that's the problem mine has, I'm ok with doing plugs far more often. But I'll let the dealer look into this first, so they have it in the computer, so if there's a warranty issue down the road, this is all well documented.

And mine sees redline about 10x more often than that. :)

Now, what I can't account for is the first 10K miles on the car. And given that it sat on dealer lots for a couple months not selling, I'm sure it wasn't treated too nicely at that time.

But, we'll see what the dealer finds when they go looking into things.

Honestly, with the record of the S1 engines, I'd be wanted to do a compression test on ANY S1 or S2 engine brought in for any customer complaint. Even if it doesn't seem like a problem, it's a data point that can be useful when in aggregate. It's really hard compiling that sort of data together, which is especially frustrating (for the engineers) when you have a big warranty problem going on.

I've got a bunch of friends in the auto industry (domestic US companies and suppliers), and warranty issues like what the S1 engine had are hell.

OK, you can have it your way...I respectfully disagree, Frankly I don't know how "bad" yours is, I guess my experience with every Mazda Rotary made since 1969 counts for squat.

There are too many variables when it comes to something like this, Fuel, Plug condition and age, Coil and Leads.

As I said if your car does not miss or breakdown UNDER Load, then it is not a problem, you do, and I really believe you are over expecting.

Mine will "miss" about every 90 seconds, roughly, it does not bother me, as I know it is NOT an issue.

Go back a few decades when Electronic Ignitions did not exist and Mazda had the Dist Breaker Points, two Contact Sets in one large Distributor for the REAPS engines 1974-1984, and before that twin distributors . Timing and dwell and gap was very important, the odd fluff, puff and miss was far more prevalent, and Carbies..

NGK Spark Plugs back then had a miserable life span, then Platinum Tipped Plugs came in around 1976, they were the ants pants and lasted much longer.

The REAPS system 1974-85 was appalling for Pops and Fluffs, constant engine driven Air Pumps and deceleration control valves...all a headache.

Remember RENESIS at idle firing order changes, Trailing Plugs become Leading and visa versa.

Your results from the Dealer will be interesting..

BTW: I have just received a few new sets of DENSO Iridium Racing Plugs for my 8 to try, Has a very fine electrode tip of 0.4mm OEM NGK's are larger, also the Denso T&L plugs have Ground Straps with Platinum coating.

We will see how they perform?

Every 90 seconds and I wouldn't care at all. This is every 2-3 seconds at the most between misses, and some pretty good stumbles that drop the revs to 500 or so.

Also, you mention fuel up there (as well as all of the ignition system). I'm in california, known to have about the worst fuel in the developed world... Definitely a possibility that the crap fuel we have here is attributing to the problem. Ducati has a bunch of fuel tank problems right now because US fuels with heavy doses of ethanol cause the plastic to soften and swell. Domestic cars designed for US fuel only don't have problems, but neither my WRX nor 350Z have been as happy with cali 91 octane (R+M/2 method) as they are on a slight mix with 100 octane race fuel, or with a bottle of octane booster to get up into the 92+ octane range.

The emissions rules here cause the engine tuning to be on the verge of detonation at all times. Not great, and I can definitely see it being a contributor.

That's interesting, I wasn't aware of that... definitely odd.

I hope so. If they just replace the plugs and say nothing else, then I'll just expect to put plugs in fairly often. I've been spoiled with platinum and iridium plugs in the WRX and 350Z that go forever between changes. The Z was scheduled for 105K miles on the plugs, but they got swapped at 90K miles, and it made a difference. Same with the WRX. Both were heavily worn long before they got to their scheduled maintenance interval.

This may turn out to be a case where the previous owner dumped in a ton of slick50 or some such crap, and the plugs are heavily fouled, and this goes away (or at least mostly goes away) with new plugs. You said yours only does this about every 90 seconds, that'd be fine with me. I'm seeing it over 30x more often than that.

I'll be interested in seeing your results.

Honestly, in the end, I love learning about cars that I own. I have no problem tearing down carbs, rebuilding motorcycle engines, etc. It's all a learning experience. That'll be this. It may turn out to be some odd side effect of the renesis engine's firing order at idle vs. off-idle. That's STILL interesting to me.

My biggest pet peeve on any forum is the "they all do that", without an explanation that would pass muster with someone with a degree in mechanical engineering, and a focus on automotive design (not me, exactly, I'm a compE, but all my friends in school were there for ME-Auto).

They may very well all do this. Ok, no big deal, I'll understand that then. And I'll be most comfortable if that's coupled with an understanding of the why of it. Motors aren't magic to me, they're pretty simple once you dig into them. And with your experience, I'm sure you've dug into them.

But from someone new to a forum, without having figured out who can really be trusted and who can't (yet), everything said by everyone is taken with boulder of salt.

The first time I dug into carbs I thought "why does anyone think these are simple". Frankly, I still think injectors are simpler than the set of circuits and venturis required to implement a CV carb. It's just harder to see where the problem is without a debugger.

Ok, it's late at night here, and I'm deep into rambling.

Judging from what I've seen of spark plugs on this site, even those who regularly drive their cars quite hard and redline often still show considerable carbon buildup on their old spark plugs. So, it's pretty obvious that only so much carbon can be cleared off the plugs only from hard driving.

For the first 15,000 miles it was easy to maintain a flawless idle by an occasional run to redline. As I approach 30,000 miles it has become more difficult with diminishing returns, so I'm planning to replace the plugs at 30,000. All things considered, it couldn't hurt to manually clean the plugs every 15,000 and replace every 30,000. Best to gently use a soft toothbrush and carb cleaner, taking care not to damage the electrode surfaces and coating.

The rotors inside the engine only turn 1/3 the eccentric shaft speed. If your idle is 800 rpm, that means the rotor is only spinning approx 266 rpm. That's pretty slow to get a good stable combustion especially if your plugs are a little worn.

On top of that, the spark plugs fire many more times than a typical piston engine. A piston engine will have one spark plug per cylinder. In a rotary, you have three separate chambers per rotor, but the same spark plug has to fire the all three of them by itself.

Those plugs are normal. Shows too much idling and city driving.

Need to redlinng more. Once a week is not enough to keep the plugs clean.