I did a few 'fixes' yesterday and now the car is running rough - in best tradition I changed multiple things at once, and now want a bit of help where to look first. It's a 2004 UK 231 RX8. Track day due on Friday - not panicking just yet!

It started straight up from cold, but then once I got above 4k revs it was sluggish which made me think the SSV, but now it seems generally a bit sluggish lower down the revs. Sometimes it got better higher up the revs, this inconsistency is making me think the coils/leads. It took longer than normal to start from hot - which is again, making me think sparks. It idles OK (not great, but OK) (this is one thing I wanted to fix with the coils).

I changed the upper intake manifold for the updated (2007?) one, with the extra port from lower down the filler neck and pipes to the LIM (I know from my last car this helps stop the catch can overflowing from blowby from sideseals), and swapped the coil packs and leads for some used D585s. Before all this it was running OK, with a slightly low idle and occassional cut out at idle, and a bit of blow-by filling the catch can and usual mayo in the dipstick/filler cap. It now has the breather pipe from low down the filler neck to the accordian pipe, and the breather port from high up on the filler neck to the catch can and then to the LIM.

The inlet manifold involves removing a number of vacuum lines and the three vacuum solenoids under the manifold - would these give CEL if I mixed them up or didn't plug anything in? Are these codes just for the electrical side of things or is there a sensor for confirming these valves have moved (eg the vacuum pipe is unplugged!).

My plan is to double check the HT leads, check for sparks with timing light, then check for all the vacuum pipes, then, if I really have to, check vacuum solenoids .

Can anyone tell me which of these could cause a CEL or which could be faulty with no CEL, and basically where I should look first to see what vacuum pipe or plug lead I've not plugged back in. They are in order I think is likely, but happy for thoughts!

Switched plug leads
Loose spark plug lead
SSV vacuum line
SSV electrical plug
Switched SSV and APV vacuum line
Switched SSV and APV wire
Missing vacuum line in intake
Missing part of VFAD

Anything else to look at before pulling it apart again? Thanks!

 

Some of the things you could have mixed up might give codes, others might not but still cause a problem. For example you won't get a code for a vacuum leak, but if one is present it will make the car run rough.

Can you restate in as few words as possible, what the actual symptoms are? There is a lot going on in your first post.
For example, what does 'idles OK, not great" mean?

 

The symptoms are hesitating acceleration, more noticable in the midrange, but not quite right throughout the range. Not clearcut hesitation - it may be fine for a few minutes, then not again. It does accelerate up to the red line.

It idles around 750rpm. It has been doing this for the last couple of months. I'd rather it idled a bit higher.

I've only owned this car a few months, but had another one for several years before.

 

750 is the correct stock idle rpm. You can increase it with an ECU tuner.

I would gather data with an OBD reader. Fuel trims at idle, fuel trims and airflow while it's hesitating and while it isn't. That'll shed more light on what's happening.
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How quickly is your catch can filling?

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Thanks for the thoughts Loki!

I've just been out and connect a vacuum gauge to the SSV and it doesn't activate until over 7k revs (with car stationary) which coincided with the engine popping and really picking up. I thought I must have screwed up the vacuum pipes. The car did seem better at higher revs earlier today which fits with this when both SSV and VDI open all is fine, but not when one or the other is open. It doesn't fit with sluggish starting, but maybe a different problem with d585 coils.

However, with the manifold off again the vacuum lines are correct. Blue to at top air pump, white in middle with white spot on hose to the ssv (the easier of the two actuators to reach with connection coming off at 90degree), and black to the vdi (tucked further under the inlet with the connection coming up out of the centre). That puzzles me a lot. Maybe it is the coils after all... But why the activation of the SSV at such high revs?

Catch can wasn't filling very quickly - just a few 100ml over a couple of months, suspect it was all from one run. Seafoam helped - after I first got it (before putting the catch can on) it had a bad burp of oil on the drive home! My old RX8 filled the catch can quicker, but the updated intake fixed that, hence transferring it over. I don't believe this is the (main) problem.

 

The thing with oil burping is it's often a symptom of compression loss. Blowby forces oil up the vent line under high rpm. Of course, it could also just have been overfilled.

But yes, probably not the root cause of the sluggishness, but it may modify how much you want to invest in troubleshooting the ssv problem.

In addition to gathering OBD data, how about the solenoid wiring? Possible the solenoids for the SSV and VDI are flipped? Possible the vacuum accumulator back there is cracked ?

 

Happy days. It's fixed. I took apart upper intake manifold, and looked fine. I swapped the coils and leads back for the originals. It looks like it is the coils or leads or operator error - i didn't hook up the timing light. I don't understand the SSV vacuum, but it should have thrown a code if it really was bad.

I'd like to get to the bottom of it, but with trackday on Friday I'm a bit wary of fiddling much more. Although the 20k mile old RevC coils in my old car are tempting and I'm getting pretty quick at switching them over.

 

You need to fix the SSV before even bothering to get on a track. It’s stuff like this why your engine is puking oil and needing a rebuild. Half the problems with this car is the people who own them.

you do understand what the SSV does right? It controls when the secondary ports open and allow air flow into the engine. The engine runs on the primary ports up until around 3500 - 4000 rpm, then the SSV opens to allow more airflow through the secondary ports into the engine until around 6500 rpm, then the APVs open to allow even more flow through the auxillary ports, and then around 7200 rpm the VDI opens to improve overall intake resonance to add additional air.

so what happens if the SSV isn’t opening until 7000 rpm? The engine is starving for air up until the APV opens, but the pcm doesn’t know this and is pouring the fuel and timing to it anyway.

simply put, you have no business on the track if your engine isn’t functioning properly. That’s just common sense. Unless you could care less about the engine, which may be the case.

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I do understand what the SSV does. I don't understand my vacuum reading. It is now working fine on the road throughout the rev range, and no CEL. I do not know if hooking a vacuum line to it in the garage is a fair test.

I know I don't want to be on the track with a non-functioning motor, which is why I sought help here. But I fixed it myself by reverting back to old coils.

100ml in the catch can is not puking oil by anyones definition. Mazda updated the breather system for a reason...

Thanks for the thoughts!