My Rotors My Be On Their Last Leg

I’m the original owner of a 2005 RX-8 and I’ve got 242,000 miles on it.

The original engine blew its brains out at 85,000 miles and Mazda comp’d me with a rebuilt engine from their Kentucky facility so I’ve got 157,000 on this rebuilt engine.

I’ve got about 530,000 total miles of rotary experience so I’m really sensitive to their little idiosyncrasies and several months ago, I got my first “ut oh” moment while driving up a long freeway grade in the heat with a fairly heavy load and the car started to knock (our very own Aircooled happened to be on-board at the time BTW).

I immediately reduced power, turned off the AC, and went to a lower gear to get the torque load down. The instruments remained nominal and the check engine light didn’t come on so I changed my plugs and wires and put the episode behind me until yesterday.

It’s super hot out here in California now and while driving up a long steep freeway grade, the engine started to surge moderately (not pronounced but unmistakable) and after it settled down, I found that I was missing a lot of power…I’ll roughly guess that I was left with about 60% of it.

I got home, let the outside temperature come down and tried to restart the engine…it came to life but it has significant issues. I drove the car around and I had about the same loss of power and I was able to invoke the knocking momentarily on another long, steep freeway grade.

It’s Saturday, everybody is closed, so I’ve got some think time.

What say the hive…go straight to a compression test (I don’t have the special tester needed for a rotary) or look at MAF, O2, or something else.

I'm considering Tri-Point in the San Fernando valley...does anybody have good or bad things to say about them?

Thank you in advance for your guidance

How old are the coils? Those are a known wear item on these cars and can lead to additional problems when they get older and weaker.

And here I was going to say, "Big deal, $30 each at Rock Auto." Good luck, man.

Duke wrote: And here I was going to say, "Big deal, $30 each at Rock Auto." Good luck, man.

That's what I thought the title ant too, haha. Good luck, I know nothing about them. I think I would love an rx8 but am terrified of the rotary.

I'll be the one to say it...

LS swap.

Agreed with RX8driver and moparman both - might be time for an LS coil swap.

Something like this: http://www.normalexception.net/index.php/mazda-rx8-diy/rx8-ls2-ignition

Bad coils tend to break up when hot.

For what it's worth, I did the LSx coils on our RX-8 and have been underwhelmed. I would have just gotten a nice new set of Mazda ones in retrospect. What you describe doesn't really sounds like a coil problem though. If it's really knocking, that's a fuel or timing issue.

I had a loss of power and surging (at very high load/high rpm) issue with our car about a year ago. Turned out the fuel pump was giving up the ghost and just couldn't maintain high enough pressure. Swapped it out with a new one and fixed the issues. It's worth tracking down the right tool to open the stupid fuel tank cover, if you give that a try.

Weak coils will also lead to weak compression, somehow. I know a bit about rotaries and even I don't quite get what voodoo is going on there, but new coils and running for a bit will bring the compression back up. If it was coils causing the low compression.

To all,

I changed the coils 2 ½ years ago so I’ve got about 60,000 miles on them. The car consistently displayed a range of RPM’s that it liked…it was bogged down below ~4.5K, would catch its breath and zoom up to ~6K, and then it would start knocking at ~6.5K.

The last time I needed coils, the symptoms were all centered around starting and cold idle. However, rotary engines have leading and trailing plugs in each rotor chamber so individual coils are doing very different jobs.

Anyway, thanks again for all of your guidance and please let me know any other thoughts my might have.

Nah, the plugs are doing the same job: igniting a mixture. If anything the trailing has a more difficult job because the chamber is under higher pressure when its spark is due. There's a direct correlation between pressure and voltage required to jump the gap.

Knocking at high RPM is very bizarre. Generally speaking, at higher speeds, things are moving too fast for detonation to even occur. And at any rate, that isn't something that should be caused by weak spark or weak engine, on a nonturbo mild-port engine. Something else is happening.

Knocking at higher RPM sounds like a fuel thing to me.

Update…I dropped my RX-8 off at my local Mazda Service Center on Sunday afternoon and they got back to me a little while ago.

They were able to replicate the power loss at low RPM’s and the knocking at high RPM’s. They collected a bunch of diagnostics on a dyno and were able to rule out the ignition system, clogged cats, etc. I didn’t get a complete answer about the fuel system but either way, they conducted a compression test and the values came back between 6.0 and 6.4 where the target is 7.5.

Obviously, these values aren’t in PSI so I’m guessing they’re in Bars (1 Bar = 14.7 PSI). Anyway, a rebuilt engine all up with parts, labor, tax, blah, blah, blah is going to be around $6,400 and based on KBB, I think the car will only be worth around 3K or something so it’s effectively totaled.

I’m thinking of buying my wife a new Explorer and seeing what they’ll give me on trade for my RX-8 and moving into her old 2003 Explorer to buy myself some think time.

Talk me out of it guys…I love rotary powered cars, I love Mazda's, my 1987 RX-7 made it 286,000 miles on its original engine and still had reasonable compression when I sold it but the Renesis has been a real turkey; two time loser in my experience.

What say the hive???

Added later...I'm fine with advice on what I should get but that's not the pressing issue...in the next 24 hours, I need to decide to either junk it or save it.

RX Reven' wrote: Anyway, a rebuilt engine all up with parts, labor, tax, blah, blah, blah is going to be around $6,400 and based on KBB, I think the car will only be worth around 3K or something so it’s effectively totaled.

How do you figure?

Does KBB own your car? Does KBB define what you want? Is KBB paying for it, are they the ones driving it?

The answer is no, no, no, and no.

I never understood the "it costs mroe to fix than it's worth" math. Of course it does. If it isn't fixed then it is worth nothing. And used car "values" are a giant pile of excrement because they are a generalization, and they are based on fictitious numbers. Do you really think, say, a '98 Passat is worth $450? Of course not. KBB says so, but really anything that runs and drives and passes emissions is worth at least $2000. However once a car gets out of the dealership-lot level of trading hands and more into the private-seller role, the numbers skew down because of the common practice of misreporting the sales price in order to cheat a little on taxes.

In reply to Knurled:

Only thing that makes sense would be that weak coils equal weak spark, which in turn may mean improper combustion. That could lead to apeax seals etc starting to gum up a bit. Fixing the problem and running it would then help burn out any built up deposits . Similar to 2 strokes that aren't getting adequate spark. Stuff gums up in them pretty easy.

Just gotta point out that 1 bar is 14.5 psi ...

Do you love the car? Willing to pound another 150k on it? If so? Fix it and rock on. It'll amotorize the motor cost to just about nothing.

If not, dump it and move on.

moparman76_69 wrote: I'll be the one to say it... LS swap.

Maybe try the old ATF or seafoam trick and see if the compression improves. Also a rebuild shouldn't cost anywhere near $6k

I am thinking fuel, spark (coils are 60k old) I have seen others fail with less. Then a atf/seafome treatment. The only other thing could be the ecu temp sensor a bad map sensor or a air flow meter.

I would find someone with a good diagnostic computer and log as much of the sensor data and study it.

A few grand for another 150k wouldn't sound terrible to me.

Hi Knurled,

I totally agree with you about the car being worth whatever it’s worth to me rather and what KBB Et. Al. claim it’s worth.

However, if gets totaled, stolen, or if I want to sell it for some reason, I won’t be able to recover what I spent on the engine rebuild...I’ll get pretty much whatever KBB Et. Al. sez’ I should get.

The timing is terrible as I just put on nice new Yokohama’s and struts all around, new clutch, throw out bearing, pilot bearing, and some other minor stuff. Brakes were done last year so they’re at 90%, blah, blah, blah AC blows a hard artic wind, gears are smoother than a buttered baby’s ass, blah, blah, blah.

It really looks and runs great except of course for the engine.

I'd still try putting a set of coils on it, or LSx time.

From an insurance claim perspective, keeping records of recent work goes a long way.

RX Reven' wrote: However, if gets totaled, stolen, or if I want to sell it for some reason, I won’t be able to recover what I spent on the engine rebuild...I’ll get pretty much whatever KBB Et. Al. sez’ I should get.

The thing is, though, that is true no matter what. If they valued the car at $10k and you spent $6k on the engine, you won't get $16k. You'll get $10k, meaning effectively refund on the work done and $4k for the car... You'll still come out "ahead" relative to where you were, financially, before the repair, but that only assumes that the car is free to you.

If you want to dump the car because you want to for various reasons, by all means do it. That should be the only justification you need.

Personally I'd invest in a can of carb cleaner and go to town cleaning the MAF sensor, then spray a bunch into the engine while it is running to clear carbon out, along with a half quart of 2 stroke oil in a top-off of the fuel tank, to see what it does.

The symptoms seems suspicious to me for it to be engine, but on the other hand 150k apparently is pretty well on up there for a 1st-series RX-8 engine.