White Exhaust Smoke & Other Issues

[whodvethought]

Hi all, hope you're all having a fantastic day . My car should be celebrating its 50,000th mile but instead, I've got a myriad of issues that have all seemed to crop up at around the same time and seem to be getting worse. I've tried researching around and have already tried several things, but I've finally relented and thought I'd pick the expertise of somebody here .

Here's the symptoms:

• Loads of white exhaust smoke on a cold start. And I mean a lot. And it has a horrible fuel smell. The car has always done this a little bit and I just wrote it off as the car running rich and the cat not being up to temperature, but the smell has gone from a little bit of fuel to unbearable, and the there's so much smoke that it will basically engulf the car if it's stationary and the wind is blowing the wrong way. What's interesting is that it all completely goes away once the car has properly got up to temperature and the exhaust smells of nothing (hence me thinking the cat was just cold). However, if the car is still warm and gets started again after around an hour or so, the smoke will be back (although not as bad). Is this supposed to be normal? I can imagine a little bit of smoke from condensation and the car running rich, but this seems a little excessive. I guess the good news is that I don't think it's burning coolant, and the smell isn't coming from the cabin (although it will make it inside if I e.g. turn on the windscreen demister and forget to enable recirculation).

• The car is beginning to struggle on cold starts. It's not dramatic or anything, but the car has gone from starting within a couple of cranks of the engine (usually in less than a second) to now hesitating a fair bit, usually taking a good couple of seconds. Hot starts are completely fine (for now). Again, nothing super major, but the car has deteriorated in quite a short amount of time.

• Power loss in the middle of the rev range. The car seems to have lost power between 4-6k rpm. The car accelerates just fine, but you don't get that 'exponential' acceleration feeling until much higher in the rev range. At very high rpm (7,500+), I get all the power back very quickly.

• The car struggles to idle. The car used to idle readily at around 800 rpm once it was warm, but now it's struggling to do so. From a cold start, the car will hover around 1.3k for ages before eventually settling down to 800. However, if I rev the engine at all and then drop it, the car will again hover around 1.3k before slowly finding the idle again, which I'm sure didn't happen before. When the car is eventually idling, it essentially tries shaking itself apart. It always did this, but it again seems to be getting worse. If I give it revs in neutral, the shaking goes away, but again if I let the revs drop, it will take a while to find the idle again.

• The car also seems to struggle to get going. I've found I have to give it a lot more gas to get it going, otherwise the car will stall. There have been a few occasions where the car has randomly stalled when moving off.

• Really bad fuel economy. Now, the car never got good fuel economy or anything, but the fuel economy has dropped significantly. We're talking a quarter tank for a dozen or so miles!

• Finally, to top it all off, and on a somewhat unrelated note, I seem to be getting the dreaded gearbox synchro issues, and they too seem to be getting worse. The gearbox has gone from not wanting to shift into first gear if I'm at higher speeds to basically not shifting into first at all when cold, and even when warm, refusing to shift into first if I'm above ~5 mph. How screwed am I when it comes to the gearbox? I've found I can get it to shift into first if I double-clutch it into gear, but then I get stuck in gear and it will refuse to shift out of it. I can live with it for now, especially since it seems to be relatively usable when fully warm, I just want to know whether anybody else has had similar issues and whether it's doomed to just get worse and worse? All the other gears are completely fine.

Okay, so now that's out of the way, here are some of the things I've considered:

• The ignition! Some of these problems presented themselves several months ago (such as the power loss, degrading starts, dodgy idle, etc.), although not as severe. I ended up re-doing the ignition works with a new battery, RRP MK4 ignition coils, Magnecor HT leads and new NGK iridium spark plugs. Interestingly, the problems seemed to go away for a while, but have come back with a vengeance. Long story short, I don't think it can be the ignition, since it doesn't even have 500 miles on it.

• The cat being dead. I was at one point convinced a dead cat was the cause of all my grievances, and I was nearly ready to buy a new one. However, I have no P0420 code and have not noticed a sulphur dioxide 'rotten egg' smell from the exhaust; it just smells of nothing when warm. I also took it on a hard drive and looked under the car afterwards, and the cat wasn't glowing or anything. I even tried this one trick I saw on Essex Rotary where you hit the exhaust pipe to check for bits of broken catalyst, but no dice there either. So I thought I'd double-check on here first.

• The MAF sensor. I tried cleaning the MAF with some WD-40 contact cleaner and did the brake pedal trick to reset the fuel profile, but the problem has remained the same. I also drove while logging the mass air flow rate from the OBD and the numbers look fine.

• The SSV. I did consider a blocked SSV potentially causing the power loss and would explain why the power comes back at high rpm, but it wouldn't account for the other issues (dodgy starts, bad idle, etc.). There's also no code being thrown for the SSV.

• The fuel injectors. I've heard leaky injectors can leak fuel into the combustion chamber, leading to white smoke when the car is started, and clogged injectors can lead to reduced performance, rough idle, etc.; but I seem to be getting the symptoms of leaky and clogged injectors at the same time! Is that even possible? From what I've read, the injectors aren't really a 'problem component' on the RX-8 like the coils are, and the power does come back at high rpm, which I'm not sure would happen if the injectors were clogged. However, these are my #1 suspect at the moment.

• The fuel pump. I know a bad fuel pump can also lead to degraded performance. The car hasn't had the fuel pump recall done yet, although I do plan on doing it soon (once my local Mazda dealer decides to pick up the phone!). I'm not sure how pertinent the fuel pump is to all of this, however; especially since the power seems to be fine at high rpm.

• Engine mounts. I did think the engine mounts were a little bit tired, hence the shaking at idle. However, I think it's probably something more than that now, although the engine mounts are probably not helping.

• For the gearbox issue, I swapped out the oil for some Redline MT-90 and the gearbox went from basically unusable when I bought it to absolutely fantastic. However, in the ~1,000 miles since then, the above issues have manifested themselves.

Some other things to note:

• The car is a 2008 S1 231PS (so the 6-speed gearbox).

• There are absolutely no lights on the dash and no trouble codes coming through my (admittedly limited) Bluetooth OBDII scanner.

• I do run a fairly heavy premix (around 400:1). I don't know if that has anything to do with it?

• The car was compression tested around six months ago with good results (all 7s from what I remember). I do plan on buying my own compression tester and testing it again at some point.

I'd really appreciate it if somebody could help me out here. I genuinely love this car and although the problems seem relatively minor in isolation, I'd want to get it fixed as soon as I can, and don't want to leave it until the small problems become insurmountable problems.

Thanks everyone!!

[qwakers]

I'd start by checking the ignition. Failing plugs leads or coils could cause most of your issues. And new doesn't guarantee good.

[whodvethought]

I'd start by checking the ignition. Failing plugs leads or coils could cause most of your issues. And new doesn't guarantee good.

My second check would be what the fuel trims look like, as I'd suspect injectors.

[Nickp47]

Sounds like you have a couple of issues there. The power loss in the mid range does sound like the SSV is stuck. It’s an easy thing to check , if it can be moved by hand it’s probably fine but I suspect if you try and move it you’ll find it’s stuck.


Re the syncro, I have used Xado alongside a good quality oil with good results , though this was more to deal with crunching in to gear rather than getting stuck in gear.

Re the smoky starts, it’ll likely boil down to ignition (perhaps a lead has come adrift or is not secure?) or injectors , could you upload a video?

[whodvethought]

Thanks all! I'll take a second look at the ignition when I find some time and will check the SSV as well . Does anybody here know of a decent way to check whether the ignition coils themselves are bad or not?

[Zxninja]

Thanks all! I'll take a second look at the ignition when I find some time and will check the SSV as well . Does anybody here know of a decent way to check whether the ignition coils themselves are bad or not?

Dr RX-8 wrote: ↑Fri Jan 30, 2026 11:59 am
What is the best way to test coil packs?
https://www.ebay.co.uk/itm/111987798367
Dave
The Spin Doctor ™

[350matt]

The stench is likely unburnt fuel from as others have said from a faulty ignition system, its also quite possible the cat is past its best
I'd say to replace the plugs with new genuine articles and use some of the plug testers to see if the coils are all working

whilst the plugs are out then do a compression test whilst you're there. you don't need the special mazda one, a normal 10 quid gauge with the 1 way valve taken out works well enough

[whodvethought]

Hey everyone! So I found a little bit of time the other day and decided to turn the wheel all the way to right and try to re-seat the HT leads in case they had come loose. Unfortunately, that didn't work, so I plan on properly testing the ignition with the tester over the weekend. However, I noticed that the little plastic clip that holds the piece of protective fabric over the spark plugs had come loose, and over my test drive had fallen off. Does anybody know where I could get a new one? I tried phoning my local dealer but they had no idea what I was talking about!

EDIT: I found this website: https://vehicleclips.co.uk/collections/ ... -bc1d56145. They seem legit, I'll give it a go

[qwakers]

they are just standard trim clips. loads of different styles and sizes.

[HarSc]

EDIT: I found this website: https://vehicleclips.co.uk/collections/ ... -bc1d56145. They seem legit, I'll give it a go

Bought many hundred bags of clips from here, all bang on. Only place I get mine from. Good price too, and UK stock vs aliexpress stuff.

[whodvethought]

Hey everyone, so I spent all day today looking over the ignition system. I visually inspected all the spark plugs and they looked fine. However, my HT leads had somehow managed to get tangled and were tensioning on the sparks. I managed to loosen them by pulling on it from the wheel well and pushing it down from the ignition coils. I then used the spark testers and ran then engine and they were all relatively bright and (more importantly) all the same brightness. I then put the HT leads back on the plugs and ran the engine again, and the car seems to have been mostly fixed! The cold starts are now significantly better and the car idles much cleaner and without as much vibration. The power has also returned and the car doesn't feel lethargic any more . I think one of the leads had lost contact with the plug and me reshuffling everything had fixed it. Thanks everyone for your help!

However, the car still smokes and smells of fuel on start up, but I think that just might be my cat being a little tired - I'll probably have to look at replacing it at some point. Another thing I forgot to mention is that when driving, I'll randomly hear a bunch of metallic rattling or 'pinging' noises that seem to come from the passenger's wheel well. The car still does this and I'm concerned that it might be the leads potentially arcing? It almost sounds like dirt or rocks being kicked up from the wheel into the wheel well area, but only happens on the passenger's side, and will randomly appear for around 30 seconds before going away again. Has anybody faced a similar issue? Any help here would be appreciated .

[qwakers]

they will always smell fuelly on startup, even with a good cat. the cat has to get up to temperature before it starts catalysing, and ironically, one of the strategies that mazda use to do that is to make it excessively rich at startup.

[350matt]

if you have deleted the secondary air pump then that adds the extra air to achieve post combustion in the exhaust , without it she'll be rich

also worth chucking a bottle of injector cleaner in there too, as dribbly injectors can give these symptoms too

if you run the engine in the dark and open the bonnet to take a peek , you will see any 'arcing' as blue sparks / flashes from the plug leads

if this is present then get a set of Magnecors on it post haste!