Yup lots of city driving and traffic.....that is what I get for living in San Francisco. In addition to being on a dealers lot for a year. Engine is running a tiny bit smoother at idle though.

Dealer update: Carbon, lots of it.
 

They're done with the car, although I haven't picked it up, yet.

They did the following:

1) reflashed the ECU
2) de-carboned the engine
3) replaced both leading plugs

Interestingly, the tech noted for the service writer to ask me if I had ever used anything less than premium in the engine (that would be a no).

I'm most interested in that ECU reflash, I'm curious what engine parameters were changed (but I'll probably never find out).

I'll pick up the car tomorrow, and post how different it idles after that.

I recorded this after 30 min of thrashing the car without any mercy. idles smooth as silk.
http://www.youtube.com/watch?v=jpuvzNKmatQ

Picked up car from dealer: definite improvement
 

The bit misfire events are all gone, now. Definitely a big improvement.

Here's the writeup from the work order:

Parts used are:

2 0000-18-N3Y8 SPARK PLUG - LEADING
1 0000-77-A86 ZOOM POWER ENGINE CLEANER

you need to take the baby to the redline more.
mines done 16k miles no misfire.

Tell that to the previous owner...

My commute is half two-lane twisties, and due to the pouring rain this time of year, best not done too spiritedly, but spiritedly enough. Then the freeway section (the other half of the commute) starts with as WOT of an on-ramp trip as I can get away with, followed by 3500-4000rpm cruising. I'm pretty sure my driving is aggressive enough to keep the engine running hot and clean. If it's not, the fuel bills are going to be getting bigger... :(

But 10K miles of it's life was someone unknown, and who knows how they drove the car. They sold it after driving it 10K miles in 9 months. It was carboned up before we got it. I noticed it was misfiring the day after we picked it up, it just wasn't enough of a problem to warrant an immediate trip to the dealer, as I'd already scheduled maintenance for it.


The only worry I have is how engine braking effects carbon buildup. Our house is at 1200' elevation, it's a half-mile 30% grade (average) down to the highway, then a climb from 500' up to a 2600' pass and then down to 200-300'.

So, from a cold start, we're engine braking a very rich engine down a 30% grade for nearly half a mile, and then it's usually (this time of year) still too cold to open up for another couple miles. My commute gives me a couple places to open it up fully, but not many. So it gets opened up each time I hit those. One intersection in the mtns, and then a freeway onramp, which being uphill, gives a nice long load for getting up to redline in 3rd. But if my wife takes it, her commute doesn't give her a safe place to open the car up really at all, too much traffic, no passing zones, 35mph speed limits or less, etc.

But now that we've reset things (hopefully), we'll see how just our driving effects the carbon build-up in the engine.

How to de-carbon 2009 S2?
Can we use MAZDA Zoom power engine cleaner?

Yeah, they used the Zoom engine cleaner. I assume this is their version of Sea Foam and the like. Spray it into the intake with the engine running, watch all the pretty smoke come out of the tailpipes. May or may not involve spraying lightly at first, and then drowning the engine in it to stall it out and let it sit, and then a later restart.

I got a LOT of practice with that sort of stuff with my truck that had a two-part intake manifold, steel and aluminum, so the gasket between the two would push out over time due to the different thermal expansion rates, and then it would suck oil out of the lifter galley under the intake manifold.

The rotary engine runs hot and runs rich at idle so don't let it idle like a normal car you will burn out the CAT and coke up the plugs. The coolant fan only kicks in over 90'C but thermostat opens up around 85'C. I find that when driving at speed and coming to a stop, hitting idle is pretty sweet until you get stuck in traffic which starts to idle with a huff and puff. This is my main beef with MOT centres as they don't have a cooling fan constantly blowing into the front air ducts while they idle the car and they overheat you engine and burn out the CAT in the process. Brake testing need the engine running and again they let it idle for a long time as they do the test not to mention that when they drive it of the brake test rollers they forget this engine has very low end torque and needs revs to pull out the drop down on the rollers. We need start a protest to force the powers that be have the rules change to exempt this car from a CAT. Bare in mind if you pre-mix it will also huff and puff at idle as the pre-mix oil will lean out the fuel mixture which the computer will adjust with more fuel. Best to use the highest octane fuel you can get your hands on to avoid hot pre-detonation in the rotor housing. The RX is not a car, it is a sports car and demands your attention. Oh and yes you need change coolant, i have found coolant temperature sensor reports incorrect temperature to the PCM after a while so change it.

Over 5 yr old thread bump if you didn't notice.

Yes but it is valid in google searches and comes up regarding this common issue.

Old it may be but valid in today's current search results it is. :mdrmed::rock: