wairx8

Hi everyone, recently new RX8 owner here in New Zealand.


If you like to help, but have a short attention span, then please scroll down to ***(6) &7 which is remaining issues, and a summary of details.


I thought I’d share the story of getting our RX8 and my journey so far, also get to the issue I am left with. I wrote most of this a while ago. But have added to it, now that I’ve done more and found more🤦🏻*♂️

I’ve done my best to diagnose (with the help of the info on this site), but want to check my methods and results with some of the veterans here if possible.

So let’s start from the start, as I know you guys like detail, or flame lack of details🤣 but at the same time I apologise for the length of this chapter book...(I’ve broken it into ***(numbers) to make questions or edits easier, eg, “Oh between 3 and 4 did you change X?”


So you can probably tell Ive been reading this site for a little while at least, about the last 6-7ish weeks, one week before the 8 arrived and near every day since. Obviously ive worked through some things, but there is just so much to learn about these cars and I’d rather have a rough idea and few screen shots available if problems arise in the middle of no cell coverage.

Having had a few RX7’s in my teens, but then needing to be more sensible for a while, I was long overdue to get another rotary when this opportunity popped up.

I happened to be looking at the time for a sensible, runabout type car, legal, but didn’t need to be flash. So how did that search turn into an RX8? 🤣🤣🤣

Well I saw this RX8 advertised, at a price that was fraction of its running value, 2003, auto (but that suits me these days) 166k km on Speedo, rebuilt 60k ago, legal for local laws (inspection and registrations all sorted well into next year) a couple of little scratches and imperfections relative to its age and a wee guard ding, over all, good for the price.

But there’s always a catch, it was flooded and the seller/owner was moving overseas in a few days, he had no time to get it running.

I know, I know,,, it already it sounds like it could be cover story for a more serious problem.

However, after many many questions with the seller I thought it was worth the chance and I decided that if it was more serious, then I’d either get my purchase price back in parts, or rebuild the engine and it would have still been a cheap car with a fresh motor.

The car was 2 hours away and I had no way to go pick it up myself, so I committed the true sin of buying any car (let alone a rotary) and brought it sight unseen and organised my local panel beaters tow truck to go and pick it up for me.

They took it to their yard so I could work on it there.

***(1)

So I went in pretty prepared for a deflood and start up, new battery for the 8, a couple of truck batteries to put inline if jumper cables were needed and a good charging Ute to jump to the truck battery.

I obviously checked all the vital fluids ect, (already smelled like a flooding issue). Then I pulled the plugs and confirmed it further. Obviously the plugs got a clean and (after heading away for cell coverage to check the ESS plug location) I disconnected the ESS and wound her over at WOT to spit out any fuel and the bit of brake fluid I had syringed into the spark plug holes.

I reinstalled the spark plugs, Now I had labeled everything as I removed it, but then realised that method was assuming they were in the correct place to start with, so I headed off for cell coverage again to double check coil to spark plug order.

As it happens, they were correct, but at least I was sure now.

So the leads got hooked back up and now comes the multiple $k moment....

Jumped in, turn the key, and Zoom Zoom........ we have a live one. Started up good with no throttle what so ever, a little Smokey, waited a few minutes and took her to 2k rpm a couple of times, a little rough but smoke soon cleared and off we went for a little clean out.

She was a little rough down low and once nice and warm the revs pretty much hit a brick wall at 5k rpm.

Coolant sensor came to mind (stuck in warm up mode) , but then this changed to 5.5k sometimes 6k but no higher, I thought this may just get better with time, which to a degree, it did. But..........

I also had a solid CEL, I tried the resets a few times since I’d had things unhooked, but it would always come back shortly into the second start up.

****(2)

So I needed that code read, I went to our closest parts store that advertises to read and clear codes, but oh no not this branch 🤦🏻*♂️ so plan B was to get a scan tool of some type as they’re cheaper than a read with a mechanic in 3 weeks when they book you in.....

So I ordered a heads up display unit that can read and clear codes, nothing too flash but shows more than enough for now.

While waiting for that, I cleaned the MAF, double checked that the spark leads were clicking tight on each end, while at it I found a vacuum leak in the top of the accordion hose, fixed that and felt a little different again, reaching 6k most times but still no higher, still a bit rough or lagging through most of the rev range though.

Heads up unit arrived and when I checked the code I got a P0031, front HO2S sensor control circuit low.

I tried cleaning the sensor........ I had to at least try,,,,, but it made no difference. Still CEL on second start, same rev range available.

So I figured without this working properly, the car won’t be learning like it should, hence the sluggish feeling and brick wall effect at 6k.

***(3)

So I got a new sensor and installed it, did the brake pedal stomp, started and warmed her up then did a couple of starts and boom CEL again, this time it was P0030 for the circuit problem......... and the test drive yielded no change either.

(Turned our that I hadn’t read enough and I now have a useless “universal” sensor here. 🤦🏻*♂️). They say it’ll work, but then won’t return it now that it’s been fitted🤬🤬


So a bit more time on this site reading and another day goes by to cool the engine down, we have another look at it, this time armed with the info on how to check the O2 harness.

I unhooked the O2 harness (front) and did a few tests.... (I needed to redo them and write them down so I can put the test results on here) because IF I did the tests right then I was fairly sure I’ve got a power short to ground and/or 2 other wires have a short to B+ so if that’s right then there’s 3 of the 4 wires touching each other somewhere in the Loom. 🤦🏻*♂️. Not blowing fuses though so the power short to ground could be me testing wrong.

So looking at the job of tracing the wires I realised it wasn’t a job for that day. Especially since I wasn’t 100% sure that I’d tested it right yet and wanted to double check what I’d read.

*****EDIT. I think some of my tests were wrong. Keep reading for new tests******

So we put the days efforts back together so the car was at least usable in the mean time, then while checking the O2 sensor connection on the bell housing, I noticed a hose end and a “spare” nipple on the underneath rear of the upper intake, in the same area.

Now I had assumed that my son, my wife or I had knocked that off while unplugging or plugging in the O2 plug. (I need my helpers due to the big hands/small space issue that is well known under these bonnets/hoods)

I hooked the hose back up and started her up again.

After this it seemed to idle a heck of a lot better and once warm the rev range seemed much smoother. (Of course I’ve since read that the particular hose goes to the vacuum chamber for some pretty important intake valves🤦🏻*♂️🤦🏻*♂️🤦🏻*♂️🤦🏻*♂️🤦🏻*♂️🤦🏻*♂️)

Needed stuff from town so went for a drive, (25km of hill driving to nearest town) and holey heck, I have a full rev range, not only that but when I get to 6k it just takes off, the engine/exhaust even seems quieter between 6-7 than it does at 4-6.

So now I’m thinking the vacuum hose had been off the whole time 🤦🏻*♂️🤦🏻*♂️ because I still had the P0030 CEL with the new sensor and it was still staying in open loop all the time. So I don’t think the O2 sensor fixed any of this. The original P0031 also returned with this sensor in place.

Anyway, a bit of time goes by, as we have other things to do as well.

***(4)

I decide a full day is needed (I don’t work fast now) so I can remove UIM and start with some loom dismantling to find some rubbed wires.

I figured if I’m going that deep, then it’s a good time to do an oil change, re clean MAF and intake, cleaned the throttle body, moved the SSV and VDI valves while spraying them with throttle body cleaner too, clean and re-oil the air filter. I also put the original O2 sensor in again. While this far, I also ended up removing, cleaning/sanding and dielectric spraying any ground wires I could find.

Tested for vacuum leaks with brake cleaner and engine start when finished.

Again I ran out of time and had to put it back together without getting more tests done.

So I still got P0031 and occasionally also got the P0131. Sometimes both, other times just one.

***(5)

Turns out I had to redo at least some of this a few days later as the air filter oil fouled the MAF 🤦🏻*♂️ and was running like garbage under 4K rpm.

So while redoing this I finally took the mid pipe out to check if there was still a CAT in there, (the old owner said “he didn’t think” it had one) but with no rear O2 code showing I figured I must have had one, so wanted to check the CAT, turns out it was already gutted, so that’s that sorted.

Anyhow, all back together again, again...... and just the O2 sensor codes P0031/P0131 are still there, however, still full rev range, but definitely felt like it has a little more to offer me.

***(6)

Right so, finally today, I have tested the harness “properly” for open circuits, shorted grounds, powers or shorts to either.

Now what I have come up with is some tests that half match the “fail” status of testing, but don’t quite match, also the failed tests don’t necessarily match the codes I’ve been getting, and this is where I think the PCM may be the issue.

When I test for continuity between O2 harness terminal A and ground, there is continuity, (which there shouldn’t be) however when I disconnect the plug containing (2B) from the PCM, there is no longer continuity to ground.

So with (2B) plugged back in, the o2 harness terminal A stays in contact/continuity with ground unless the very left hand side plug to the PCM is disconnected. This remains the same even if I ground the body of the PCM. The most left plug on the PCM is still what contacts O2 harness terminal A to ground.

So the short to ground isn’t between O2 terminal A and PCM (2B) it seems to be deeper than that where the problem is. As the faults for P0131 are to test for and repair short between the 2 terminals.....


But wait there is more......

So with the ignition off, testing between terminal D on the O2 Harness and ground has continuity, again this should be, this is unless I disconnect the plug for terminal (1V) from the PCM, if i do this, then again the harness itself has no continuity to ground. But between the terminals is not open circuit.

So with (1V) back into the PCM, O2 harness terminal D shows continuity to ground, until the second from the left plug is removed from the PCM, even with the PCM body grounded directly, no other plugs change this.

Now this is a partial match for a test for P0032, which I’ve not had show up at all yet.

So I have 2 grounds on the O2 harness that shouldn’t be, but it seems the problem is in or past the PCM, as it’s not shorted direct to ground via the body of the PCM (if that’s possible) but they are shorted to ground via one of the wires in the left or second from left PCM plug, (plug, not terminal).

***(7)

To summarise,

2003, Auto, right hand drive, 166k on body, 60k on engine,

Purchased flooded, got going easy, with cel, and vacuum leak, sorted vacuum leak

CEL was many different O2 sensor DTC’s 0030, 0031, 0131,

Tested via all procedures for codes shown and some that didn’t show,

Front O2 sensor harness has 2 wires grounded that shouldn’t be, but it’s not between there and the PCM, and failed more tests than just the codes shown.

Gutted CAT, no rear O2 CEL,

K&N pod filter

Recent oil change, without any difference to symptoms, other cleaned items, some twice after my K&N oil amount complication.

Last owner says he put coils, plugs and wires in within last 6 months, however if they ever show a symptom I won’t hesitate to take the records with a grain of salt. I’d even do them soon anyway as a preventative, I just want to get rid of this CEL first.

Recent work not listed above,

between ***(1) & ***(2) I had 1 new tyre fitted.

Between ***(4)&***(5) I had 3 more tyres fitted and a 4 wheel alignment, neither of these made any difference in the way it was running at the time.

Between ***(3)&***(4) I hooked the boot release up to the alarm remote button 2.

Between ***(6)&***(7) taught my son how to break into an RX8 after he locked the keys in the boot when using the remote to get tools and car was still locked🤦🏻*♂️🤦🏻*♂️🤦🏻*♂️. Spare key and remote are on the list......

Anyway, sorry this is long as, but I’ve read about every post I can find on rewiring/changing/testing Front O2 sensors, ect ect, opened all attachments, even looked at some rear sensor threads in case they developed into my type of wiring issues.

I also know that without details of what I’ve done, and not done ect that there isn’t as much help available.

I think the answer and advice could be as short as “Replace your PCM” but I’m hoping someone has had this issue by now and just not posted it up on here. Perhaps it’s more or less trouble than the PCM, but buying parts too quick can be a mistake too.🤣🤣

That’s probably enough to digest for one sitting anyway. I appreciate anyone who is still hanging in there.

Brettus

iTrader: (2)

Can't help you much on the o2 sensor other than to say ...have you tried a known problem free sensor yet ?
Did want to mention that you need to get rid of that pod filter setup as that will certainly be causing some issues on it's own . Either find and fit a stock intake or build yourself a new setup . If you go onto purelyrx8 website and search 'brettus' you will find my DIY for making a cold air intake that actually works properly.

wairx8

Thanks for your help.

Unfortunately unless I buy one for $630+ gst and wait 6 weeks for it to arrive from Japan, then apparently I won’t be getting an OEM one, so I don’t really want another sensor here that I can’t return IF it’s not the problem, secondly I don’t know anyone with a known good O2 sensor to borrow, or that would have been one of my first options too, can’t even find a genuine second hand one to try.
It’s almost cheaper to try a second hand PCM (other than having to have the dealer program it in)
Just a bit strange with the harness failing the tests for the code, but I’ll get there I guess.

As for the pod filter, I had read before that the stock set up was pretty good originally, however this came with the pod and some type of cold air intake, I’ll get some pics of that too, but if I can find a stock set up soon I would have no issues going back to it, I definitely don’t need the wow factor or anything that doesn’t work as good as stock. I will check out your posts for your CAI.


Thanks Again,

Brettus

iTrader: (2)

Where are you ? I have a spare 2nd hand one here in Hamilton you could borrow . Although it's not been tested.

wairx8

That’s really generous, thanks for the offer, unfortunately I’m just out of Wellington, in the Wairarapa.
If the offer did still stand, I could pay postage both ways for a test run off course, but I’d also understand if you didn’t want to send it too far away either.

The cost of a new sensor is one thing, but having it fix the problem or not is another thing. I have found some a bit cheaper than the Mazda Price I mentioned above, but I’m more weary of the fact that they may not all work the same as the Mazda one.

I’m sure a second hand genuine one would come up eventually, but it would probably be a fast moving part and/or still dear because of that. Hard to say, but confirming the diagnosis is more crucial, the dearer the parts get 🤣🤣

That being said whenever this gets solved I’ll possibly make the savings in fuel pretty quick rather than waiting for a cheaper sensor to come available, or save even more if it turns out to be a wire somewhere and don’t have to buy another sensor.

wairx8

A note to add, (whether relevant or not).

At the oil change/service time in ***(4)

I also cleaned the ESS

Any electrical connections in the loom that I came across also got opened, checked visually, cleaned with contact cleaner if need be, then either dielectric grease or WD40 used on them before closing them up again. Including power steering.

Applied WD40 to all door, boot/trunk and bonnet/hood-hinges, release latches/handles and locks.

Double checked all fuses with multi meter and added a fuse to the front lighter/12v socket.

Blew out the radiator (air path) with compressed air, same for the oil cooler.

Extended the overflow hose to a safer location.

And did another brake stomp even though the battery was out completely and Grounds under there and air box tray also cleaned.


(No wonder I ran out of time to do all the tests on the O2 Harness that day🤦🏻*♂️)