Troubleshooting My RX8 (cold-starts fine, idles, warms up and stalls))
 

Hiya everyone,
After a long time lurking the forums and the occasional PM. Figured it was about time for me to post something.
What better post to start with than a story of "How my RX8 almost died on the motorway (then actually died when i got off at the next exit)"

So yeah, the story begins with me going home from a day out and a fairly long drive. ~20km or so...
I was on the motorway going up a hill, when I heard an unusual (and unintended) backfire. "That was odd" I thought, but paid no mind at first.
Second time it backfires, "something's definitely up, I need to check on this when i get home."
Third time, and the revs start dropping suddenly too. Then power comes back for a second or so, the revs drop again, power comes back, then drops again... and so on.
I find a place to stop on the motorway, shut everything down, and wait.
Few minutes later i fire her up again, no problems, and carry on towards home.
Everything's until the next off-ramp, the backfires come back and the revs start dropping once more.
I get off the motorway and into a side street, the RX8 dies. No more starts, I wait for a tow.

That night and following day I spend researching and talking to a few friends about what the problem could be.
Basically, it's one or more of the possible four possibilities.
Vacuum line leak, fuel pump, fuel filter or something with engine.
There's a few links and bits of info I find on each of the four, here and elsewhere on the net.
But the topic either changes or the thread updates just stop... "WHAT DID YOU ALL FIND?"
So, I'm making this thread. Will go try to catalog as much as I can when I do it.
I don't want to drop the car to the mechanic because three of the four I listed I could probably fix myself.
The engine.... i may need help with :hahano:
The aim is to explore, learn and get my RX8 back on the road. (and maybe help someone else in my situation) :fingersx:

I drive a 2006, Type E, RX8, AT, mostly stock (i think). Got it at 80km on the clock, now (4 years later) ~124km.
Engine compression tests (roughly every year) have so far been good, never had any starting issues hot or cold.
Around the 100km mark i managed to get my hands on some BHR coils and a year-ish later the BHR mid-pipe.
That's about it, really.

Wish me luck.

Compression can hold being good, but it is possible for it to suddenly drop due to seal failure and/or detonation damage. Wouldn't hurt to compression test again just to rule that possibility before getting to far into diagnosis or repairs

A compression test is a good idea, I’ll need to get a compression tester for myself.
Wonder if there’s one on sale in NZ...

I was finally able to go through everything on the list to troubleshoot the 8 and see if I can get it going again.

Went through the list top to bottom....

1. Checked for Vacuum line leaks - didn't find anything
2. Cleaned the MAF sensor - didn't seem to have any effect
3. Checked ODBII for any error codes or something when it stalls - all clean
4. Cleaned each of the plugs - they were pretty gummy so cleaned them up too.
5. Checked the each plug with a 'spark plug tester' - This was interesting... the leading plugs had the tester lighting up nice and bright, but the trailing ones barely glowed... is that right? any one experience that, or am i looking at a set of new coils? :confused:
6. Checked compression (poor-man's method) - disconnected all plugs from coils, took out the leading plug and cranked it. 3 good sounding puffs in from both rotors. (i'll book myself in for a proper compression test soon)
7. Changed the air filter (it was dirty and it was on the way ;) )
8. Finally, gave her a 20L can of 98 octane fuel.

The RX8 roars, back to life! and stays alive! :ylsuper:
Me and a mate are looking at each other going... "what?" We initially suspected bad fuel was the cause.... but wrote it off because I had been driving on it since full (the tank was showing less than a 1/4 when i started having issues)
So we're standing there, going... Ok, do we dare try a test drive?
(After checking I had roadside rescue) I got in and went for nice, long a drive.
No problems, even shut it off for a bit, waited and fired her back up.

After all that, the RX8 continues running fine and we still don't know what the exact cause was...
So yeah, thanks to this forum and a couple cool folks who gave me a couple ideas the RX8 is alive and well. :mdrmed:

Now to keep it going.... (and figure out why the trailing plugs barely lit up the plug tester)

When in doubt, replace the coils. Cheaper than engines ;)
If you really want to narrow it down, swap the rear coils to the front and see if the faint spark travels with the coil.

Glad you got it running!

Yeah, that's very true.
I might get a set of new trailing plugs as well... could be one or the other :)

I am very happy to get it running again!

Don't forget about the wires. But just a simple swap front to back will tell you exactly what the culprit is

Yeah, good point about the wires.
I’ll get it all checked :D

After checking everything and getting my RX8 running, the fuel level drops to a quarter tank and the car starts sputtering, backfiring and everything.
just like when this whole thing started.

At this point I’m suspecting bad fuel and get the tank pumped dry.
fill up with with new 98 and go for a drive.
A week down the track, I’m at a quarter tank again...
guess who’s back? :eyetwitch

so now, the plan is put a little fuel in to get it above the quarter mark.
Connect up my ODBII and see what the sensors are showing when the backfires start.

After that, it’ll be off to the mechanic I think... as I’m all out of ideas... :scratchhe

if you are testing the trailing firing while cranking the engine, they will not always fire,or will scatter spark lightly ( Apparently)
its mainly the leading that starts the engine

Oh, that actually explains a lot of what I was seeing then
Thanks for that :D:

The working theory at the moment is a malfunctioning fuel pump.
Suspect that it’s overheating or something similar is happening... Which when the fuel tank is full isn’t a problem... the fuel cools everything off... The pump happily works away doing it’s thing.
Dropping it to a quarter tank stops the cooling effect and the problem surfaces.
So this week will be to get my hands on a second-hand fuel pump to make the switch over the weekend.

Should probably invest in a fire extinguisher while I’m at it... ;)

The weather finally clears up and I can work on car... yay!

problem to overcome now... how the hell do you get the fuel pump lid off? :scratchhe
i see online there are special wrenches for it... has anyone found a way to get away without using one?

I think its easier to use the special tool,
its possible these days there are cheap tools available that will do it,
but I am not sure

Yeah, I found the tools... now to wait for the shipping to go through haha
in the mean time... just have to put up with the wonky fuel gauge, I guess :eyetwitch

The tool has arrived and I was finally able to get into the tank(s).
Got my replacement fuel pump and fuel sending unit ready.
Turned out there are two... one on each side, so that was an interesting discovery... I only had the right hand side one.

(FYI The two have different orientations and twist on/off in different directions)

Anyway, the fuel line going to the right-hand side was a just a loose bit with a guard/grill on the end.
The replacement was a stand with a fixed location for the fuel line to (end? Pick up the fuel from? What is that bit called?:scratchhe)
Had to do a bit of a hack to get it all to work... the fuel line is really tough plastic and it looks like it’s a 4mm diameter stretched and crimped over an 8mm pieces on either end.
So I snipped off the bit on the end (there was plenty of slack), got a larger piece of fuel line and made a bit of an adapter for the fuel line and the plastic grill bit. (tightened both ends to prevent them slipping off)

Put everything back together, and tried turning on.
The 8 roars back to life without much cranking! :D:
Warmed her up... all good... Took her out for a test drive... all good... pretty happy to have my 8 back :D:

Filled up half a tank... now to drive around and see if it’s all fixed.
Here’s hoping!! :fingersx:

sound liek a good result

Yeah, I’m pretty happy with :-D
Just hope it stays a good result. Haha

Hopefully the documentation helps someone else out in the future. :-)