FYI - I have heard of similar problems on 350Z's which caused similar issues. Improper torque of the crank pulley bolt caused the keyway on the crank and the pulley to wear over time, resulting in a wobbly assembly and the inevitable code.

As much as I love additional info to vehicle problems I am unsure of how this applies to our issues with the ms3. Being somewhat of a mechanic and tuner myself and experiencing the problem first hand I don't think what you are describing is the issue here. It is a form of fuel cut that only starts after the vehicle is fully warmed up and only gets worse the longer it runs until it eventually starves itself of fuel and dies.
Also it isn't throwing a code at this point, something I find kind of odd. I am unsure of what AW has found since they have had the car back but I'm willing to bet they are more stumped than ever. I am suppose to discuss the details of what they find wrong with it today and will post what I find out later on.

I was just chiming in on the flywheel topic - an imbalance of the rotating assembly (on either side of the crank) can lead to really wacky timing which can cause the car to break up and trip the misfire code. It seems like Mazda knows more than we do (shocking) and likely knows what batches of flywheels are affected.

Agreed, it doesn't sound like your issue - do you have any method of data logging? I wonder what the fuel pressure looks like when symptoms appear.

UPDATE:

So, its been a few months (8!) since we've had the MS3 back and in good order.

The dealership replaced the wiring harness and said that it was good to go. We where skeptical. Wiring harness? Really? But, since we've had it back, 0 issues to report.

We have since bought the newest Cobb tuner, stage III CS intake, and have been using a prototype unrestricted single exit exhaust. Next step is the fuel pump internals and down pipe.

Sorry its taken so long for us to update, life has been busy for us and the car has been perfect, we have pretty much just been waiting for something wrong to happen again before we posted that it was in such good condition, and luckily, we have no complaints. This car has turned out to be quite the STI killer, there is nothing I love more than to beat an STI kid. Lol.

The build will be posted once we start building greater than the Cobb tune and intake mods. Thanks everyone for the support! :You_Rock_Emoticon:

Any idea how they diagnosed the wiring harness, or how much it would cost to fix out of warranty? I had attributed the P0300 my car threw every once in a while to burning through plugs (happened about every 15k miles, replace plugs, and I'd be good for another 15k).

Now, the car is out of warranty, and the code is back with 3000 miles on the plugs. . .

I've seen the flywheel mentioned too, with no real explanation about how it happens, but the idea of paying to have the flywheel replaced sounds like it'll be painful for my wallet.

The dealership was not upfront with how much the harness was, they did try to say it was around a grand when we tried to get them to just give us another MS3 for replacement of what seemed to be a lemon. We stuck with the car and its fine now. If they did anything else to the car, it was before the issue arose for the second time, before it was fixed for good. Perhaps someone can shed some light on the harness issue potentially being the fix?

As far as your engine code, have you checked anything else that comes up with that code?

Here's a quick list of what comes up under that engine code. Just changing the plugs may not be good enough.

- Faulty spark plug (s)
- Faulty ignition coil (s)
- Clogged or faulty fuel injector (s)
- Intake air leak
- Fuel injectors harness is open or shorted
- Fuel Injectors circuit poor electrical connection
- Ignition coils harness is open or shorted
- Ignition coils circuit poor electrical connection
- Insufficient cylinders compression
- Incorrect fuel pressure

There is a how to on stretching the spring in the coil wire for better contact.

Shouldn't a bad coil or injector give a specific cylinder too though? It's only ever given P0300. I just moved from a house to an apartment, so I don't have a place to work on the car myself. When I had the house, I stretched the springs in the ignition coils

I'm taking the car to the dealer tomorrow. Hopefully they won't try to blow me off since the car is out of warranty and they stand to make money by fixing it.

Random-Misfire Page

Quick reference^

thanks for that. I'm thinking a vacuum leak is unlikely, because it idles fine and the code only seems to be triggered at highway speeds. I know the EGR likes to get stuck in our cars, so maybe it's just that.

Time for an EGR delete

you mean I shouldn't pay them $500 to clean my EGR pipe?:jester:

if that's what is, I'll have an awesome excuse to do a delete and add an AP. Problem is, it's going to be a week and a half and ~1200 of driving before I have a chance to do it.

EGR delete, valve cleaning, and an OCC were on my to-do list for this summer, before I sold the house. Of course, after I don't have a place to work on the car, and since the warranty is expired, stuff starts going wrong.


update: because I know somebody else will have the same problem and probably search for it. The dealer says the P0300 was being triggered on deceleration. Their story is there's a TSB about something being off with the ECU parameters causing the random misfire. They're fixing it relatively cheap (under $200), so I'm happy

Glad they aren't trying to screw you over, that's a good deal

Doesn't an EGR delete throw a CEL? And it's required for emissions, if that is required where you live...

I know how much that harness costs. Ask me how I know.

Yes it does and, I beleive regardless of your location it's against the law to mess with the emissions system. I think the only place that enforces is commifornia

It's illegal in many states. Heck, FL legally cannot have an afrermarket exhaust!

Isn't it technically "illegal" to have a modified exhaust in any state? Most just don't enforce as rigorously (or at all) as others?

Yeah pretty much.

It can be modified as long as any emissions isn't tampered with or compromised. Also, there is a decibel level restrictions as well.
Although, the cops won't mess with many domestics (excluding nobalts and peons lol) for having exhaust but, they'll probably be a dick if you're in an import. Subject to vary Depending on your location. In TEXAS so, lots of 'MERICA here.

I'm sure if you had a improved emissions system, you would be within the law and also gay. Fuck nature, racecars.