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To my wife’s dismay I’ve recently found myself in possession of a 2004 RX-8 😊
I’ve always been sworn off rotaries but have always been curious and had an opportunity I couldn’t pass up. Yes I already have way too many projects but I love restoring vehicles and watching them come back from the grave. I’m hoping I can do the same here.
Over the years I’ve had some reasonably unusual vehicles (starting with a few XR4x4s in England, a Robin Hood, imported Mustang GT to England, all the way up to a V8 Swapped Miata that I currently race States side).
Upfront I want to thank the members of the forum for such a great resource. It’s been a decade or so since I have found a community that obviously is very passionate about this vehicle (and wants to see others succeed). I understand the need to read everything I possibly can before asking questions. I’ve been through the “Start here” thread and many of the linked + others that are of interest. My reason for creating this thread is to make sure I am on the right track and have not mis-interpreted any of the knowledge shared. There’s a ton of it out there and it’s been addictive :D
Anyway enough about that, here’s some background on the car:
2004 RX-8 Manual with 18” Wheels (from what I’ve read that means it has an LSD etc)
Close to 119K miles on the clock
Many owners!
History
From looking at the service history and speaking with the owner it sounds like it started running into issues 3-4 months after buying. I’ll summarize what I can but here is the current condition:
Clutch is completely gone (no bite and acts like it has a torque convertor!)
Smoke from exhaust after 30s from startup
Needs an oil change (6K since the last one, was changing at 3K but stopped)
Oil consumption has increased
Cat after having been replaced was still glowing
Suspected to be low on compression (more on that in a mo)
And here is the maintenance history:
New battery, coils, wires (but not plugs?) 2 years ago at 100K
New Cat, air filter, cleaned MAF (and replaced o-ring) 1.5 years ago at 107K
CEL misfire cylinder 1 at 106.5K. Owner cleaned sparkplugs and it helped
Fuel pump replaced and fuel sock cleaned 107K then 68 miles later CEL:P0300. Owner put old coils back in and CEL cleared itself
Compression test at 108K. The test shows that it fails but if I use the convertor in the Newbie page for rpm/alt it comes out at 85-100psi. Still not great
Seafoamed @109K (but reading the forums I understand a single can/treatment wouldn’t do much)
Symptoms
Rough idle when warm – stumbles, goes to die
Won’t start when hot
Said Cat was still glowing
Revs smooth (didn’t rev it too high) but has what sounds like a lose heat shield on the exhaust – worried this is actually the noise people talk about in the glove box!
I appreciate that none of the above looks good and from what I have read on here it is very likely that a new engine is required. I see that they go for ~$3K. Before I do that I wanted to try some of the advice from everything I have read. It looks like ignition health is top priority (along with cooling system and frequent oil changes).
Below is my plan. I just thought I’d post it to make sure it made sense. After I execute it if it is still bad then I know it will mean a new engine.
Install OBDII reader with App to watch coolant temps and monitor O2/fuel trims etc
Check ignition health/coils with OTC ignition tester – Replace coils and plugs as necessary
Flush/inspect cooling system (with Mazda FL-22 coolant recommended in one of the threads) – replace any lines/overflow tank that have any grime
Reset fuel trims
Check battery health
Check starter health (logging RPMs when cranking)
Clean battery terminals and all grounds (using star washers and dielectric grease… works wonders on the TL1000R!)
Premix with Idemitsu
Oil Change (stock filter, 5W30 Mobil 1 Synth – it is getting to 100 in KS at the moment. I have read many of the threads about conventional vs synthetic and have also read the 540rat blog… that took some patience! I may switch to conventional pretty quickly if everything goes well)
Mazda Zoom Engine Cleaner
New plugs (it looks like some of the things above can foul them)
Mid pipe de-cat (I’ve read it’s not worth trying to gut the current cat).
Clutch replacement (OEM)
Depending on how all of that goes I am tempted to try the ATF trick (with the old plugs) but can see it’s pretty controversial. At that point I guess I’m thinking I’ll have nothing to loose.
Should a light be seen at the end of the tunnel I then intend to tackle everything on the below list that hasn’t already been done (as well as addressing the cosmetic issues and A/C… we need A/C in KS!). Once that’s done it’s going to a dealer to get the 3 open recalls addressed (airbag, fuel tank leak, lower am ball joint)
30,000 miles:
- Replace Ignition coils
- Replace Plug wires
- Replace Spark plugs
- Clean MAF (mass air flow sensor)
- Clean ESS (e-shaft sensor)
- Reset ESS profile
- Clean power steering connections
- Clean battery terminals and clamps
- Replace transmission fluid
- Replace coolant (Mazda FL-22 is highly recommended)
- Replace air filter
- Replace brake fluid (fluid in the brake lines AND the clutch line)
~$300 USD in parts if you shop smartly.
every 60,000:
...all 30,000, plus...
- Clean all chassis electrical grounding points
- Replace accessory belts
- Clean OMP lines
- Replace rear differential fluid
- Replace thermostat
- Clean / Straighten AC condenser fins
- Clean / Straighten oil cooler fins
- Inspect catalytic converter
- Clean / Inspect intake valving
- Consider / inspect all points in 90,000+ as well, many items fail early
~$130 USD in parts if you shop smartly.
90,000:
...all 30,000, plus any 60,000 not yet done, plus...
- Replace coolant bottle
- Replace radiator hoses
- Replace radiator
- Replace front O2 sensor
- Replace motor mounts
- Inspect clutch pedal assembly for flex / weld breaks
~$900 USD in parts if you shop smartly.
At 100k, anything original in the cooling system is really suspect and failure prone. It represents the biggest threat to your engine.
Let me know if I'm vaguely on the right path!
Last edited by GeicoGecko; 01-25-2021 at 05:12 AM.
Welcome to the forum!! You are on the right path! Though the use of synthetic oil is a very controversial subject. Read up on that subject. I'm a conventional oil type of guy and perform frequent oil changes on all of my rotaries. Would also love to see pics of your new 8!!
Since the 90's I have personally used Marvel Mystery Oil instead of ATF to help decarbon engines. Has worked great for me on many 7's and a couple 8's. The engine that I installed in my black 04 has sat for a long time but had decent compression pulses. I put the MMO in the housings through the leading spark plug holes and reinstalled the spark plugs. I would turn the engine over by hand every day, sometimes adding more. About a month went by and I stripped the engine down to a bare block, cleaned the auxiliary port valves and intake manifolds, SSV, installed all new gaskets, spark plugs, etc and I installed the engine after powering the starter and cranking the engine over without the plugs and that removed most of the MMO. The engine came right to life and smoked like a freight train. Its ran excellent for the last two years. A recent compression test with my rotary compression tester yielded fair results.
With that said, you may want to check the engine's compression before getting crazy. Plan on buying a replacement engine for the car, new or used
Thanks for the reply. Sounds like I need to do more research on the oil front. I did see that Mazda actually changed their tune in later manuals and added that you shouldn’t use Semi-synth or Synth. It must have been for a reason!
I won’t be able to touch the car for a few weeks. Trying to fix up the racecar for the next race and then I have to do a timing belt on the truck. That should give me lots of time to research
On that note I wonder if it’s worth running MMO/ATF through the car while it sits? Our driveway is pointed downhill (front of the car is down) so not sure what effect that would have?
I tried replying back with some photos but it said it had to wait for moderator approval. I must have missed something in the rules. As soon as I work out what that is I'll get some snaps up.
[left]Thanks for the reply. Sounds like I need to do more research on the oil front. I did see that Mazda actually changed their tune in later manuals and added that you shouldn’t use Semi-synth or Synth. It must have been for a reason!
FYI, my '05 Owner's Manual – and the Product Update DVD mailed to me shortly after purchase – recommend non-synthetic oil. Go to about 4:50:
It can't hurt to put MMO in the engine while it sits. Be sure to turn the engine over to spread the oil around inside of the engine. I prefer to do this by hand. The MMO will help to dissolve carbon inside of the engine, helping to free stuck seals. You will have to pull the plugs and crank the engine over to remove most of the MMO. This is done as a deflood procedure and the 10A fuse is removed so that no fuel is injected into the engine when cranking. Once the engine starts, there will be smoke and lots of it. This is normal.
I had some chance to start working through the list. Thought I'd document my findings here if they were ever of use to anyone.
OBD2
Installed my old and trusty ScanTool OBDLink MX. Normally use this with PalmerPerformance ScanXL (I have the enhanced Mazda diagnostics from an old Miata) and Torque on Android. It was being used on a new laptop and for some reason it was really struggling to maintain BT connectivity. I tried the normal Android phone with Torque but that wouldn't connect. Ended up switching back to an old MacBook running XP in bootcamp and it worked just fine... very strange.
Found a DTC P0506. It's an old one as the CEL hasn't been on recently. Figured it must be from the poor idle when hot. Cleared it - haven't seen it since.
Starter RPM
Looks like the starter has been upgraded at some point. The model number on the top is N3Z1. On cranking it will turn 225 rpm. From everything I've read that's on the low side. The battery seems OK but I would like to get a log of the cranking voltage. Unfortunately I didn't enable this PID until part way through the last log so haven't got it.
If it looks good I'll probably switch to the N3R3 starter. From what I understand this has the highest output and is more reliable. 225 RPM with Current Starter
One thing I did find was that the starter wasn't always engaging on a key turn. I had removed/replaced it (to check the part number and look at the clutch with an endoscope). It seems like the solenoid ground is the culprit. When it wouldn't start I'd nip underneath and give it a wiggle and voila. I cleaned up the spade and it appears to be better but we'll see.
MAF
Next item I tackled was cleaning the maf. When I removed it I discovered it to be as clean as a whistle but figured it couldn't hurt to clean it with MAF cleaner. Upon restart it looked like it ran at 5g/s whereas before it had been at 6g/s idle. Admittedly the environmental conditions and temps weren't identical so I don’t think I can draw any conclusions.
Ground Point Improvements
This appeared to have the most impact. I removed every ground I could find in the engine bay (2 on the passenger wing, one on the passengers strut mount, one connecting the intake to the chassis on the passenger side, one on the drivers wing) and also cleaned the earth strap at the back connected to the exhaust.
Each connection had some paint removed to allow metal/metal contact, threads of the screws wire brushed and conductive grease applied.
Upon restart I would appear that the idle became more consistent and less hunting. I say appeared as earlier in the evening I had removed the battery connection to remove the starter. This cleared the LTFT so at first the engine wouldn't idle. Looking on the forums I found a couple of threads talking about holding the RPM manually at various throttles until it would idle. This did the trick and actually loaded the long term fuel trims. They seem a little high (>20%) but at least it's idling again. I'm curious at what everyone else normally finds for LTFTs?
For reference if anyone needs it:
Allow engine to warm up (if it doesn’t idle hold the throttle to maintain 750-1000 rpm).
Rev to 2500 rpm and hold for 15s
Rev to 4500-5000 rpm and hold for 15s
Slowly back off the throttle to 1000 rpm
Gradually remove more throttle until you reach 750. If it starts to dip add more throttle to try and maintain 750 rpm. Keep trying (gradually) to remove throttle until it idles without input
Before: Wavy idle before grounding points cleaned
After: More stable?
Coolant Pressure Check
After the engine cooled it was onto the coolant pressure check. Using the Stant Pressure tester (12270) with the correct adapters (12021 & 12027) I was able to confirm that the radiator cap was good and that the system held 18psi without any decrease (left it for a few minutes).
As it's been so long I decided to change the oil (even if I have to do it after the de-coke) as I didn’t like the idea of running it much longer with the old oil. It was very dirty as you might expect. The filter is a bit of a pain but looks like I need to get an F-type wrench.
I also added some premix and a little new fuel.
Glued Connection + Missing Connections - Electrical and Vacuum?
Whilst poking around I found a couple of missing connections and what looks to be vacuum ports. I also found a connector on the intake that appears to have been glued. Can anyone help identify?
1. The below is a shot standing on the driver's side looking across the engine. The connector on the intake appears to have glue holding it in?
2. Behind the airbox appears to be a missing vacuum line? (circled in red) Should anything be connected here?
3. Coolant level sensor? From what I've read these aren't reliable but shouldn't it be connected somewhere? No connection
4. Looking down behind the airbox - Missing connector? Missing connector behind the airbox
Nasty Exhaust Noise
Finally I think I've found what is causing the exhaust rattle. Where what I believe is the mid pipe joins the rest of the system there is a connection that is spring loaded and has lock bolts. When the car is running it is at this point that the exhaust rattle is coming from. Is there a trick to getting this to stop?
Clutch
Ordered the clutch, pressure plate, release bearing, pilot bearing, oil seal, pilot bearing removal/installation tool, 54mm socket and the flywheel holder. All the parts are OEM and the rest is from mazdatrix. A little more than I was expecting but hopefully it will last a while and will make the job a doddle.
I took the car out before working on it last week. At 40mph the clutch was pretty engaged and I was able to wind it up to the redline without issue. I know the numbers on a couple of the rotors looked a little on the low side before but we will see!
Happy Saturday! Hopefully everyone is out driving and enjoying their RX
Last edited by GeicoGecko; 02-06-2021 at 11:01 AM.
Reason: Formatting issues
So going through the workshop manual it appears that 2. Above is part of the VFAD system. Searching through the forums it appears as though there is some question as to whether removing this aids overall power. I will check if the other end has been capped correctly. I assume for now it has as there would probably be a vacuum leak if it hadn’t. I will check the rest of the system to see if it is intact. If it is I’m tempted to put it back into service.
Installed the clutch over the weekend. Wasn't quite as straight forward as I had hoped! I had a new flywheel so wasn't worrying about marking the old one. No matter how much or hard I hit it it wasn't going to budge. Ended up finding that an old hub puller (probably from England) that looked like it would work. However even that was bending and not moving the flywheel. Whilst under this tension though a small hit with a hammer and voila.
Old hub puller inverted and minus the bolt!Reconnected the VFAD system and took it for a drive. All appears to be working well so far. The starter RPM is still a little on the low side so will probably end up replacing that.
Next is measuring the ignition health (although truth be told I'll probably end up just replacing the coils, plugs and wires!)
That plastic connector on the intake is like $10 from the dealer. I broke one a while ago so I know. Hopefully, you can take it off with all the glue.
The male coolant reservoir connector comes out from the ECU unit. The PO could have unplugged it due to a faulty level sensor that would light up the coolant level low light on the dash even when the level is good. Unfortunately, you will have to replace the entire reservoir to replace the sensor. Highly recommended, though. A $100 something bottle is cheaper than an engine replacement due to overheating.
That connector behind the airbox is fake. If you look inside, you won't see anything electrical.
And AFAIK VFAD is said to control the noise level during lower RPM according to official materials. Hard to say if it contributes to performance.
Last edited by UnknownJinX; 08-06-2018 at 06:19 PM.
Took the car out for a 70 mile drive last night. Mix of highways and back roads. Catalyst temp sat at 1609 when cruising at 70. Coolant was bobbing around 200.
I did see a P0171 at one point but didn’t realize I should have grabbed the freeze frame. It was only present on startup when I stopped to fill the tank.
Fuel economy average was hanging around 30mpg on cruise but not sure I believe that! I'll find out next fill up
It took a little longer to start when hot but it wasn't horrible... Still plan on de-coking and now I know everything is working I'll order new coils, plugs and HT leads.
Last edited by GeicoGecko; 08-08-2018 at 05:22 PM.
Performed the engine decoke using the Zoom Zoom Engine Cleaner (following the DIY on here of course). The idle is now smooth and the LTFT for idle are dropping from 20. I haven't driven it much but will report back tomorrow. It feels like it has more power so we'll see!
This morning I did a dry run disconnecting all the connectors etc to make sure I could jump in and do it after warming up the engine. In the process I noticed the VFAD connection I had reconnected had fallen off. I reconnected it and secured it with a zip tie before warming it up. It didn't make a huge difference to anything before the clean.
When I removed the air filter I did notice that the clean air intake tube under the rad support (in the bumper) had a crack in it at the top. I doubt this is making much of a difference to anything but am considering replacing it.
Also changed the oil again OK so it's only been 470 miles since the last change but it was looking black! I figure at least now I may have at least 75% new oil? :D
Took the car on a 130 mile drive on Sunday. It feels so much more responsive and the idle is definitely better.
I saw a P2259 (Control B Circuit Low) which looks to be like an issue with the secondary air solenoid. I've parked the car for now and will test all solenoids before going further.
When I did the engine cleaner I did remove the airbox. I can't see how this would have affected this but I understand the wiring loom is fairly fragile. Plan right now is to test the contacts and the solenoid itself.
Finally if it's helpful to anyone I really think this technical service bulletin needs to be a sticky somewhere I get the discussions about older vs new synthetics but I can't test my oil so will stick to conventional and not risk it.
In my previous research on the site I found all of the other threads and user manual updates but it wasn't until I searched for something else that this one came up.
Just came across your blog and man should i say you do know what youre talking about not like others and their basic explanations . Hope to hear more on your working progress as my self recently got a 04 Mazda rx8 as well Semi automatic with engine light on and just today my exhaust system has a loosen ring triangle shape that looks to me it was screwed to exhaust now with that being said my rx8 has a very loud rattling sound from mid front of vehicle i stead of sound being normally back of vehicle. I did drove in freeway at between 50 - 80 mph and also uphill at 67 mph at max due to steep hill. Now im trying to figure out if i could just screw back on whats as of now hanging loosen on exhaust pipe.
Previous owner had mentioned he had changed whole exhaust pipe to an aftermarket with i think no cat not sure still trying to get all details upon past services and i do have its old exhaust pipe that was changed
07-06-2018, 12:25 PM
