Good day all,

I bought my 2004 RX8 147KW with 106 000 km on the clock in April. I live in northern Germany. Before I bought it I've had them do a compression test and the results came back fine, no less than 7.0 (done at official Mazda Vendor here in Munster). I was told the car was fully serviced, new spark plugs, filters etc.
I've bought the car not as daily commute but for long trips, holidays.
I've hesitated for a while before making this post having spent a lot of time browsing the threads here, but none of the threads I've read exactly matched what I'm experiencing. The problem started in August:
I've noticed that it took a bit longer for the car to start, hot or cold. I was spinning but it wasn't igniting. The problem got progressively worse, and there really was no difference between a hot or a cold start, both took about 3-5 seconds. Then I had to drive all the way to Estonia, about 2300km, (before the trip I accidentally overfilled my oil by a fairly considerable amount) and on the way it refused to start at the gas station. It happened once, and then I got it going again and eventually reached my destination.
So I thought: spark plugs.
Finding a mechanic to service my RX8 was not easy. Nobody wanted to touch it.. Eventually I found a guy, he changed the plugs, said two of them were okay-ish, two were quite worn, all four were wet though. He also said when he put the new plugs in it started like new. But then the problem came back again.
Next I checked the air filter and it looked like it was NEVER changed. It wasn't oily, it was just clogged with all sorts of stuff. So I put in the new filter, had the airway and the MAF cleaned. It had a positive effect, but the problem didn't quite go away. Still took 2-4 seconds to start. The guys who cleaned the air way (at a non official Mazda Help centre) said they suspect that I'm running rich, because of the way it smells. And that that could be causing the slow start. They didn't know how to solve this issue or how it could have come about..
So then I had to drive all the way back to Germany and after about 3/4 of the way I see CEL. Checked it through OBD2 and it came up with u0073 ( Control Module Communication Bus 'A' Off) & p0420 (Catalyst System Efficiency Below Threshold (Bank 1)) codes.

I gather that u0073 can simply come up just by plugging in the OBD2 scanner, so fine..
p0420 is, I assume, a consequence of having had starting issues for a while.

The car drives fine, no loss of power. Normal oil consumption, mileage is only slightly above normal (16 L/100km town; 11L/100km highway). I do not premix.
So my questions are:
1. I get no misfires, so am I safe in assuming that the problem can't be caused by a bad ignition (plugs, wires, coils)?
2. I've read about the Coolant seal failure, and I have noticed white smoke on startups on a few occasions, but it's been very humid here so I can't be sure it's not condensation. Can burning coolant clog the CAT?
(Another thing that points to the coolant is this one time I was driving in the rain and a puff of white smoke came from under the hood. It didn't last long, but it was noticeable. On visual inspection I've noticed no leaks though..)
3. Running rich. I don't even know where to start here. Can a bad air filter that's not been changed for too long a time make the computer go permanently insane and give me a bad mix? How can this be fixed? (The car does smell a lot of petrol behind closed doors for the first few minutes after I start it, but I heard that's quite normal.)
4. Could I in theory have lost enough compression in 6 months and 7000km to begin having these issues?

Obviously, I want to solve the core of the problem before I begin dealing with the CAT.
Help me establish a logical chain of thought, please!

Arthur

 

Hey there,
I hope you got you case solved but a few things
1. No bad ignition can infact cause problems without a CEL ( had a broken plug but no CEL )
2. If it doesnt continously smoke dun worry
3.This i have no experience or knowledge
4.Does the car stall when hot, are hot starts miserably long n better when cold ..? So depending on what you mention its probably not compression

This is most probably a problem caused by ignition as i also experienced smt like this n it was a combination os a broken spark plug a faulty injector and a clogged up fuel filter.

 

Overfilling the oil may be fine, so long as you do not see oil in the intake tubes. Obviously dont leave it this way. You may need to use MAF cleaner on your MAF, might want to anyways.

1. When you say that you get no misfires, do you mean codes? Or are you not hearing/feeling misfires?
2. Does the white smoke smell sweet, or burn your eyes? Coolant seal failures produce THICK white smoke. In my cases(2 cars) my car ran fine hot with no issues, but would produce thick smoke when cold.
3. I doubt a bad air filter would go that crazy, but there are a few resets you can do.
4. Compression will show symptoms in this order: Hot starts...... hunting idle 700-1200rpm......Stalling at hot........trouble cold starting.

You could have a flooding issue which can show up hot or cold. Checking the plugs when cold is the usual go to route to see.

• Coolant would be due to coolant seals failing as mentioned above with thick white smoke and smell.
• Oil could be from bad rotor control rings or from issues with the OMP injection.
• Gas could be due to leaky injectors or bad ignition/timing issues. Keep in mind that if you have coolant or oil floods, failure to start will inevitably keep dumping fuel into the engine.

I would say let the car sit overnight. Disconnect the battery, which can help reset the ecu. Check/clean your intake and MAF for oil. Check/clean the Eshaft sensor while the intake is out. You could then crank the engine by hand and pull the plugs to see what comes out. Either clean or replace them. Afterwards with everything back together, put the key into the ON position and step on the brake pedal 20x until the oil pressure needle blips(this may not blip on all cars I think)........................... If this doesn't help your problem may be deeper. Either an injector or oil injector is not functioning properly. However these steps should at least guide you to an answer if it is flooding.

Other possibilities are a clogged cat or dying ignition coils. You could try taking off the cat to see, some people report that they could see the Cat glowing and know. For the coils there is a cheap HEI tester you can get made by OTC 6589.

 

There is a list created by one of the members here of maintence items by mileage, go down the list and address the items as needed.
With no mileage listed on the coils, change them out including wires. Unlikely as an issue but the fuel pumps on these cars are subpar, might look into replacing it also.
Good luck with your 8, I love mine still after 12 years.

 

Thank you Fruitbat and 200.mph for your help, I've never dealt with aftermarket exhaust and this is all very stressful trying to choose. How she sounds is extremely important to me.

It sounds like Ineed to scratch Turbo XS off my list. BHR remains a strong candidate, I'm going to keep trying to find a video of BHR.

I did find a video with soundtests for about a dozen brands that even provided part numbers, but it seems like they are catbacks not midpipes. If I make the dangerous assumption that midpipes and catbacks of the same brand would produce similar sound qualities, HKS Legamax would be my first choice. I have not further researched it yet, but I am concerned that I may repeatedly encounter "yes that's the one I want...it's no longer in production." That's what happened when I picked Billy Boat

Has anyone had any experience with HKS Legamax?

 

Hey Mate

I read carefully what you write I didnt see something very obvious and very commom on the RX8 before 2006. The starter and baterry.
I almost bet ypu is the battery and/or starter.

 

Hello, I have a BHR catless midpipe and HKS Legamax exhaust in my rx8. I can get a video of how it sounds if you'd like. As for my personal thoughts, it's a composed but still a somewhat loud exhaust. I find it just quiet enough to drive for a long time on the highway without getting a headache, and when flooring the throttle it roars to life quite nicely. Here in Australia we still have a couple of places selling the Legamax, I was lucky to get it second hand for cheap!

 

I was going to drop the cat and gut it, and then I would atleast be able to drive it while I work on getting an appropriate cat for passing emissions...BUT IT LOOKS LIKE IT'S ALREADY GUTTED?!? I could easily just not know what I'm doing because I basically know nothing I didn't learn from this forum, but I didn't gut it...previous owner claimed he was the original owner and it was unmodified...ofc he could have been lying, but he was telling the truth about replacing the one coil pack (I changed them all and clearly one had been changed and the others had not)...irregardless of who gutted it, if I'm correct and it has been gutted it can't be CLOGGED...so if my problem is not a clogged cat, what is causing the heating under the passenger seat leading to the melting of my O2 sensor connector and the carpet fire while in possession of the previous owner???

Sorry...this post was meant for the thread about my car, not this one