KyAllroad (Jeremy)
KyAllroad (Jeremy) PowerDork
9/9/18 10:22 a.m.

So while the MX-5 is in the shop I figured i’d Shower some love on the $1,000 RX-8.

New battery and cleaned the SSV.  With a bit of cranking it fired up and idles well.  When I give it gas it has some hesitation and breaks up in the midrange but then cleans up and is smooth up in the 7-9k range.  Then when I was ready to take a spin around the block it died and would restart for a few minutes.  

Shoved it back into it’s parking spot and did more diagnosing found coil number 2 isn’t bolted down (broken stud) and that the front rotor, leading plug is cracked.

New plugs and bolted down the coil......and it isn’t any better.  

Then did the “20 brake stomp”.  It fired right up and sounded good......for a few minutes, then back to breaking up/not taking fuel/stalling.  

What next?  And why did Mazda make such a delicate flower of an engine?  

JtspellS
JtspellS SuperDork
9/9/18 11:25 a.m.

Would suggest fuel supply next. 

And sure the renesis has plenty of issues but remember you did buy a $1000 car too.

westsidetalon
westsidetalon Reader
9/9/18 11:44 a.m.

crank angle sensor 

BoxheadTim
BoxheadTim MegaDork
9/9/18 12:03 p.m.

Check the coils - the RX8 coils aren't exactly known for their longevity and only live about as long as the spark plugs (around 30k). Mine - which didn't run that bad when I got it - ran a lot better with new plugs and stock coils.

Knurled.
Knurled. MegaDork
9/9/18 12:29 p.m.

Coil is probably damaged from running with no ground.

 

The issue seems to be centered around the area of highest chamber pressure, which screams insufficient ignition.

Snrub
Snrub HalfDork
9/9/18 1:02 p.m.

I've been giving your issue some thought. The one time I had a similar issue with a rotary, to the starting and dying later  was when a fuel injector was stuck open. It would start, move around, run not hideously, etc. but then die. It didn't run smooth through any of the rev range though.

In terms of issues through the rev range, there's ~4 things that open/move in the intake tract as you rev it up, the SSV being one of them. Have you troubleshot all of them? Applied vacuum/voltage and test to each of them and the central vacum pressure tank. The VFAD can be disconnected, the vacuum hose blocked off and it will default open.

freestyle
freestyle Reader
9/9/18 1:12 p.m.

I've had 2 coil packs go bad with similar symptoms. I have the BHR  / GM versions. I used one of those old school lights that flash or don't flash to test. Both were the trailing plugs.  

Harvey
Harvey Dork
9/9/18 1:37 p.m.

Replace all coil packs as others have said. Coil packs go bad on the car with regularity. Don't run it anymore without replacing those.

You probably just want to buy the BHR coils as the OEM ones are just as expensive and fail more often.

https://black-halo-racing.myshopify.com/products/ignition-upgrade

If it is hard to start and has the original starter then replace the starter with the later version.

http://shop.mazmart.com/en/rx8-starter-new-oem-n3z1-18-400

These are things you should do regardless of whether they solve your current problem. There is the outside chance that something else is wrong, like the fuel pump, but these are the two most common issues with the car.

StillNoCones
StillNoCones New Reader
9/9/18 2:13 p.m.

I used to have an RX-8 with the exact same issues. Would run for a while then die, and struggle to restart. I changed plugs, coils, then fuel components for no luck. I would take it to a Mazda tech. took it to a tech for a full diagnosis and found out that my apex seals were toast and also clogged had a clogged cat.

I wasnt ready for that since my car had 99k and already had a Mazda reman a few years ago, but Renesis and apex seals dont get along too well.

Hoping this is not your issue but it does happen.

BoxheadTim
BoxheadTim MegaDork
9/9/18 2:53 p.m.

Well, we did make it to post #9 before someone mentioned the "A" word .

A lot of issues that look compression related on the Renesis were at least caused by ignition issues. 

Knurled.
Knurled. MegaDork
9/9/18 3:40 p.m.

In reply to BoxheadTim :

A lot of compression issues are caused by ignition.  Replacing the coils will make the compression go up after a bit of running.

 

It was my understanding that the main compression issue is the side seals, not apex.  Those thin little buggers don't take kindly to sweeping over an exhaust port.

Dr. Hess
Dr. Hess MegaDork
9/9/18 5:36 p.m.

I understand there's an trick with that motor.  It involves something called an "Ell Ess Swap."

KyAllroad (Jeremy)
KyAllroad (Jeremy) PowerDork
9/9/18 6:05 p.m.

In reply to Dr. Hess :

It’s a E36 M3ty, salvage title, starting to rust, drifter toy.  If the hard parts of the engine are toast: it’s a part-out.

wvumtnbkr
wvumtnbkr UltraDork
9/9/18 7:30 p.m.

I'm betting bad coils leading to bad / clogged cat.

JtspellS
JtspellS SuperDork
9/9/18 8:04 p.m.
Knurled. said:

In reply to BoxheadTim :

It was my understanding that the main compression issue is the side seals, not apex.  Those thin little buggers don't take kindly to sweeping over an exhaust port.

Nailed it, apex seals were old 10a early 12a issues stock, and E36 M3ty pre ignition tunes (usually) on boosted cars.

 

If you need I do have a set of used known good c revision coils I don’t have a use for after the D585 swap, shoot me a DM if wanted.

KyAllroad (Jeremy)
KyAllroad (Jeremy) PowerDork
9/9/18 8:15 p.m.

In reply to JtspellS :

I can’t imagine that would be a bad thing.  My email is armstrong390 at the yahoo place.  (Which somehow keeps me from sending DMs). I’d appreciate any help laugh

JtspellS
JtspellS SuperDork
9/10/18 11:58 a.m.

PM sent.

RX Reven'
RX Reven' SuperDork
9/10/18 4:52 p.m.

FWIW, the one time I had a stuck apex seal on my 13B, it was totally obvious as the starter motor was able to spin the engine up several hundred rpm’s more than usual due to the low compression…you didn’t even need to look at the tach, you could just hear it go weeeeeeeeee. Did the ol’ ATF trick and was back in business.

Anyway, based on the symptoms, I’m going with wvumtnbkr’s theory…bad coils causing clogged cats.

BoxheadTim
BoxheadTim MegaDork
9/10/18 5:06 p.m.

You might want to pull the cat and check before that does any more damage.

Knurled.
Knurled. MegaDork
9/10/18 5:13 p.m.

In reply to RX Reven' :

Whe says the converters are clogged?  If it can rev smoothly at 7-9k then the exhaust is not likely to be restricted.

RX Reven'
RX Reven' SuperDork
9/10/18 6:20 p.m.
Knurled. said:

In reply to RX Reven' :

Whe says the converters are clogged?  If it can rev smoothly at 7-9k then the exhaust is not likely to be restricted.

Good point however there may be nonlinear stuff going on at high rpm’s due to the additional heat changing the viscosity of the goo as well as possibly achieving some pressure threshold that changes the dynamics.

But again, good point.

KyAllroad (Jeremy)
KyAllroad (Jeremy) PowerDork
9/10/18 7:22 p.m.

I’ll jack it up and pull the cat(s) this week and have a look.  

It has a factory muffler but is really loud, I haven’t really looked yet to see what sort of exhaust stuff is going on.

WonkoTheSane
WonkoTheSane Dork
9/10/18 11:08 p.m.

I'll second (third, fourth?)  the coils.

 

Am I the only one who never had a coil problem?  I replaced the OEM on my 07 at 60k with OEM rev C, and I didn't notice a difference.  I changed the plugs at that time too.  I'm only up to 80k now, but it's been fine for lots of street driving and a few track days.

Harvey
Harvey SuperDork
9/11/18 12:01 p.m.
WonkoTheSane said:

I'll second (third, fourth?)  the coils.

 

Am I the only one who never had a coil problem?  I replaced the OEM on my 07 at 60k with OEM rev C, and I didn't notice a difference.  I changed the plugs at that time too.  I'm only up to 80k now, but it's been fine for lots of street driving and a few track days.

You changed them at 60k miles, that's why you haven't had a problem.  laugh

I suppose I've seen some that had problems early on, but mostly the higher mileage ones seem to be the ones with issues.

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