Chris Luther

I have checked out these forums a bit, and still can't guess what is wrong as it seems MIAC can be caused by a number of things.

I picked up a 2006 Mazda RX-8 Shinka automatic from my mother back in February. It has 73k at the moment, when I took it over it had 68k, but had a new engine replaced at 61k. She likely drove it like it was a baby, never in high revs, but always careful with engine temp and shutdown.

I use it as a daily driver, majority highway and interstate 30-40 miles to work and back, premium only, and 5w-20 oilchange every 3k, routine topoffs between fillups. I always let it warm up to the phantom point prior to driving it and I try to push it to at least 6krpm once a day. Normal operating range in the 3-4k with paddle shifters. This vehicle has always been worked on by Mazda dealership from the point of my moms ownership forward.

I recently upgraded to Continental DWS tires, replaced the rear brake pads and bled off some of the break fluid, replaced the engine air filter, and had the AC leak-checked, evacuated, and recharged by a 3rd party AC specialist.

My issues are with a somewhat loss in power, MIAC sound from glovebox that has increased in intensity over the last month or two (can hear slushing as the car starts up and when you first accelerate), seemingly excessive heat (it has been pushing 90's here for last couple weeks), a rough idle (shakes the car a bit) with a slight drop in rpm, and a weird vibrational issue when accelerating or rolling from a dead stop that shakes the sideview mirror. I have also noticed that the shifter gets REALLY hot sometimes, not sure if that is due to ambient temp or normal.

I know mazda warranty is still good on the powertrain through next year, and there is 3rd party warranty good for the majority of the fixes if I can't figure out how to get Mazda or the Toyota dealership I purchased it from to properly diagnose the problem.

Last time I took it to the dealership I asked them to check motor mounts and heater hose orifice issue and they said both need to be replaced. What else could be wrong with this beautiful car? I would really like to take good care of it and make it last a while. (obviously)

Any similar stories/results or advice would be greatly appreciated. Thanks.

RIWWP

iTrader: (2)

Pretty solid history, but there is one critical system that you haven't even mentioned: Ignition.

When were the coils, plugs, and wires last replaced? They tend to fail around 30,000 miles, and when they fail they will cause a rough idle and power loss. The cat will clog quickly with failing ignition, which will increase center console heat considerably, kill power further, kill gas mileage, and lead to engine damage and eventually a vehicle fire.

I'm not saying that it's the problem, but you haven't mentioned ignition at all, and it's pretty critical.

Chris Luther

I was told the coils plugs and wires were replaced at new engine replacement. Yes, the gas mileage has dropped as well, I was getting around 19/20mpg and now it is down to 17.

What kind of engine damage could be occuring? Is it mainly due to heat/warping?

RIWWP

iTrader: (2)

When the cat clogs, the exhaust system pre-cat builds up a lot of pressure, and the engine has to struggle more and more to push the exhaust gases into the header. Eventually this gets to the point of damaging seals. The localized heat buildup is also harmful to things in general.

If you don't have any proof that the coils, plugs, and wires were replaced, I highly recommend you do so. You likely won't get warranty coverage on the plugs or wires as they are listed maintenance items. The coils are not officially maintenance items, so you may be able to get coverage on them. If not, you can pay as little as ~$190 for all the parts from auto parts stores, or as much as $800ish from dealers. You can replace all 12 pieces in about an hour, even if you don't know what you are doing, with only a plug socket, 10mm socket, extension, and socket wrench. No special tools required.

RIWWP

iTrader: (2)

Keep in mind that you may still actually have MIAC as a separate unrelated problem.

Chris Luther

Thanks for the help and suggestions.

I ended up having deteriorated motor mounts and needed a rear diff service. They recommended a AT-power flush, to which I agreed, but they somehow were not equipped to do that for this model year. An alternate Mazda dealership said he would never recommend a AT flush for that model year due to it's fully synthetic nature unless something is wrong with the transmission. *shrug*

I also advised them about the MIAC issues and the orifice heater hose fix. They performed all these services with the coolant flush and although the MIAC issue subsided for a while, it came back and now sounds like a gallon of liquid is slushing around in front of my stereo. When I take it to them to have them take a look at it and fix it, I'll get the car back with the heat on full blast, and no sound for a short time.

I see in many places around these forums that this is a common issue and the fix is to just blast the heater to burp out the air for a few days while on an incline or a combination of "tricks" that are pretty rediculous for hot weather summers.

Frustrated.

tpb7463

iTrader: (1)

Kinda surprised that the dealership would advise waiting until you have symptoms, more often than not (and this goes for any AT-car) flushes exacerbate shifting issues, not fix them. If you're due for the service interval, then have it done.

A lot of the "tricks" are for instantaneous relief of the sloshing. I believe there's TSB on the coolant flushing procedure to burp the air in the system (disconnecting the throttle body hose?). If you wanted a less-direct approach, you can try topping off the coolant to the fill line each time the car is cold. After 2-3 drive cycles the sound should disappear. I do that every year after I take the car out of storage and change the coolant. Avoid standing traffic in the meantime, until the sound is gone.