It probably doesn't look good that I'm posting this while actively trying to sell my car, but I'm leaning more towards keeping it if I can figure this problem out, and I'm very up-front about issues with my cars when selling.

Anyway, '04 with 134k, original motor. Over time it has become slow at highway speeds, mostly when climbing even slight inclines. I could be going on the highway at 75 MPH and floor it, and it'll take a good 30 seconds to get to 80. Motor sounds fine, it hauls plenty *** at regular speeds and on main roads, and when on flat or declining elevations goes plenty quick and uses almost no throttle. For example, my commute is 10 miles highway, 10 miles back roads. The back roads get about the same MPG regardless of direction, but going to work I get about 15 MPG, and coming home from work I get 20 (calculated using Torque).

What I've done, almost all in the past month:

• replaced coils (went with whatever was cheap at Rock Auto, hoping that they'd be "good enough" for now)
• spark plugs
• Seafoam
• cleaned MAF
• reset ESS
• gutted cat
• cleaned fuel sock
• replaced air filter

I ordered spark plug wires and will be replacing them later today. Replacing coils made the biggest difference, as the car would misfire and sound rough (imagine an unmuffled 12A) for the first 10-15 seconds of a cold start, then go back to normal.

I had P2070 come on earlier this week. I'm assuming that means look at SSV, correct? It looks fairly involved, and while it's good that I'm friends with Vyndicative here, he also set his RX-8 on fire, so I don't know if I want him touching mine.

Any other thoughts are greatly appreciated.

 

20mpg using Torque is pretty bad. When I was getting 22mpg actual, Torque would read 29mpg+. It's rather inaccurate, so an actual reading would help.

The power loss symptoms sound very much like a clogged cat, but i see you have a gutted one, so it shouldn't be that.

It very well could be an intake valving problem, as they open up by load and RPM, and without one opening up correctly, you are going to be choking the airflow into the engine.

Just to rule out the engine, I'd recommend getting a compression test. Your potential buyers are hopefully knowledgeable enough to ask for a compression test anyway.

 

One potential buyer is going to perform a compression test, which will either be really good news or really bad news. The rest...well, the market for a $4500 '04 RX-8 isn't exactly made up of the most savvy and educated potential buyers. I did tell one person who said he knows nothing about cars that this is probably not the vehicle for him, even though it's been almost entirely smooth sailing for me in 2+ years of ownership.

 

Also, yeah, Torque seems to read a bit high. 15 or 20 is my reading for just that particular trip. My math at fill-ups has been around 15.5, which is closer to the 16.6 average (well, down to 16.2 after having to drive to downtown Cleveland this morning...which has it's one bridge into the city shut down. That was fun) that Torque has been showing since I reset everything in the app at the last fill-up.

 

That mileage also suggests that something is wrong, though the engine struggling at higher RPM and full throttle will suck down fuel alarmingly fast anyway, so these two issues are likely related.

 

Rx8 engine worn out fast. thinner Chrome, short apex seal + stupid Side seal springs.

speaking of that, MSP's apex seal is such a joke, I tore down an engine about a month ago, compression was 7.5 at all faces when its COLD, cuz it's out of the car, so it should be around high 6 when it's warm.

upon disassemble, the housing obviously were trashed with fully of chatter marks, and the apex seals were down to 3.8 mm. this is probably the reason why Mazda made so many updates to the RX8's apex seal, the new one I got were Revision J, think about it, RX7's newest seal was just A-B-C, yep, 3 revision, Rx-8 ? oh man ...

As for SSS, the revision B now supposed to be much stronger than the original A, B has pink color at the tips. let's see how well this goes.

I get **** mpg like 12 only if I drive in city(manhattan) everyday, otherwise I get around 16-18 of pure city driving, pure hwy I got 27 before, which is ok I think,

 

Say what now?

 

I was saying, original MSP seems to wear out pretty fast.

did u the buyer do compression test yet?

as for Torque, that mpg function never work, at least on rx8.

 

By any chance, would you happen to know or have an idea on what revisions were used in certain RX-8 model years? I had no clue Mazda changed out the seals over the years. You learn something new everyday Lol.

Posted From RX8Club.com Android App

 

I think I'm missing something here. What is MSP? I'm reading Mazdaspeed Protégé.

 

Also, plug wires seemed to make a marginal difference. Car felt faster, but not at highway speeds in 6th gear. How fast should an RX-8 accelerate in that situation anyway? I drove the girlfriend's Jetta TDI last night and even with all that Torque it wasn't very quick.

 

well, if u can find out your engine's build date, and assume it was using new apex seals at the time, u can match it with mazda's database, cuz they tell u when it was updated.

other than that, there isn't really a way to tell.

and Mazda didn't say why it was updated, but they did it for a reason. it can't be cost, so it's gotta be durability cuz like I said, Rx7 after all these years only went up to C, rx8 apex already got up to J

Rx-8s engine code name is 13B-MSP (Multi Side Port)

6th gear is for curising highway, not for acceleration.

 

With the mileage on your car, if you haven't cleaned the SSV yet, I'd say go for it.
Its not terribly difficult to do, just takes some time and patience.
My 04' only has 63k miles, never overfilled the oil, gutted cat like you, but SSV was caked...
Check my current winter project in the multimedia section.
Getting to the SSV out was easier than getting the radiator out.
Additionally there's an excellent DIY SSV removal/cleaning thread on the forum. I just kinda winged it though.
If you do go down that route, feel free to ask questions.

 

Yeah, I feel the need to do that ASAP.

Further test driving tonight yielded wildly inconsistent results. Doing 60-80 MPH pulls with Torque gave me 4.6 sec in 4th gear, 9.x in 5th, 11.1 again in 5th, and 14.6 in 6th gear. Driving conservatively, it gets better city MPG than highway, where I have to give it 30-40% throttle just to maintain 70-75 MPH. I don't put much stock in the "dyno" on Torque, but it read 151 HP at 7000ish RPM when I accelerated onto a straight, uphill on-ramp. There were some times, mostly on the highway, where the car sounded sour at 5000-7000 RPM, but, then, a mile or so later on the main roads, sounded perfectly fine and revved smoothly all the way up to redline.

 

possibly a bad fuel pump?

 

One of the coils physically broke. I replaced it and car felt great for the 20 or so miles I drove it last night, most of which was on an stretch of road where it previously felt sluggish.

 

Wouldn't expect it to have a lot of pickup in sixth at the best of times.....6th is a maintenance gear...unless you are up around 150mph

 

Right, but there was 0 before...as in taking 10-20 seconds to gain 1 MPH.

 

Gain one mph from what speed? 145?

 

compression issues usually show up as poor idle, difficulty starting the engine and stalling conditions. once above 3k RPMs even an old tired crapped out engine should feel fairly on the ball unless it was completely lacking a rotor, which would also give those same symptoms.

 

Any issues with starting when the engine is warm? I.e. does it crank longer when warm? This indicates compression issues.

You said that you noticed a change in behaviour after installing new cheap coils and again after installing new plug leads, so sounds most like a spark related issue. Check the leads are connected properly. If you know another local rx-8 owner, swap coils and leads with them for a day and see if the issue disappears. If it turns out to be the coils and you're keeping the car, get a decent set of coils this time round - OE rev C minimum, BHR recommended, or another well documented quality coil brand.

While you're checking the above, might as well checking how dirty your new spark plugs are.

 

From around 70-80ish.

FWIW, 60-80 MPH in 6th gear took 10 seconds today, vs the 14.6 I mentioned earlier in the thread. The car feels perfectly strong (well, I've only driven 100k+ mile RX-8s so that's all I have to compare it to) through the entire powerband. But yeah, it does sometimes struggle to start when warm. It used to be just when cold, oddly enough.

 

The issue with the coils I think was isolated to one. When I took the first plug wire off, the coil cracked in half and one of the pieces fell out. I put it back in and glued it together to drive for a couple days before I had a replacement coil, and that's when it was randomly sluggish again, had a misfire CEL, etc. I've not noticed any issues since replacing that specific coil.