Well, you've got 2 things going on: your air pump is not sending air to your exhaust and you're running lean. If these faults are connected, it could be due to a vacuum leak between the vacuum chamber and the upper intake manifold. (See diagram below) No vacuum in the vacuum chamber means no vacuum to actuate the secondary air control valve. (Your SSV and VDI valves won't work either). I suggest you double check the connection of both vacuum lines at the back of the UIM. If that is not the problem, then also check for exhaust leaks. (Pipe from air control valve to exhaust manifold is apparently a frequent culprit, could be loose at either end.) It is also possible the 2 codes are unrelated, in which case Team already listed other possible causes for P0171.

https://cimg0.ibsrv.net/gimg/www.rx8...20ab7f61eb.jpg

Thanks for the suggestion, but isn't VFAD a 132 thing not present on 192?

probably, we don't deal with those much over here. The thing to do though is to pull and cap every connection on the intake to eliminate a cracked hose, bad check valve, etc.

OK, update.
Fuel pressure is low at 40 psi, but no 5-minute drop Looks like I need a new pump!

Inlet manifold vacuum 15 inHg @ idle but no vacuum detected at air control valve tubing. I need to check this again when engine has sat long enough to get properly cool - it might have been too warm this time as it was not the first thing I checked.

Think I might have cracked it. Literally.

Occam's razor for 0171 & 0410 points to the vacuum solenoid on the vacuum chamber under the UIM. So I took off the UIM, and the solenoid for the AIR system was slightly out of place and the body broken where it goes into the bung on the vacuum chamber, as in photo. I can't guarantee that I didn't do that when I took the assembly off just now, but it fits the symptoms. Fingers crossed that a replacement will sort it.

Yes, that would be a significant vacuum leak

Replacing the broken vacuum solenoid has sorted the AIR fault - the cold start AFR is now 20 and I don't get a code for it anymore. Happy days.
I wish.
Still getting lean code. Replaced fuel pump - no change.
Went round spraying brake cleaner again and sometimes get sign of vacuum leak (rev change, AFR reduction) and sometimes don't! Which is maddening! This time it was around the front of the inlet manifold.
Need to do more vacuum leak hunting, otherwise only O2 sensor or PCM left to try, but I think its a leak still, but where?! :(

You need to start at the maf and physically check every connection, hose, port, check valve, etc.

You're right, I'll do it again! Might invest in a smoke type leak detector; I'd hoped to avoid it.

Right. Update.
I have got to the bottom of it and I'm not a happy bunny!
I made a smoke generator and pressure tested the inlet side. This demonstrated a leak in the top front end of the inlet manifold gasket.
Further investigation and research and it looks like I was supplied with a gasket for a 6-port, and the engine is a 4-port. Being a noob to rotaries, I didn't spot this, just fitted it and assembled the ancillaries.
I also have an oil leak from the back of the sump gasket which was revealed when the front of the car was jacked up. That is one of the professionally built parts!

Grrrr! FFS! :wallbash: :mad:

Man, what a bummer. I feel for you bro. At least it is a 4-port though. So not having those APV barrels to deal with should make getting the intake on/off a much easier job. On a 6-port it's a real booger to do without pulling the engine out entirely. :uhh: Still not a fun job regardless.

if you're referring to the oil pan leaking at the gasket (sump gasket leaking?) you might want to consider the reusable Viton gasket that Pineapple Racing sells on their website. It makes taking the oil pan on/off a lot easier job rather than using silicone sealer, which is another pita job to cleanup after, especially if it ever leaks.

kind of surprised you haven't weighed in on my 4-port turbo engine concept thread yet ...


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Ouch. tough break.

Ooooh, you've got me intrigued - you can pull the lower manifold without taking the engine out? Really?. RotaryResurrection hasn't done a step by step has he, by any chance?
Unfortunately we've got this habit of misplacing the steering wheel, so I've got the brake servo on the manifold side which might make it worse.

Well sorry. If I understood what is being implied and your RX8 is RHD then that may complicate the situation some.

Yes it is RHD.

Might have to undo/move the steering shaft out of the way, but that’s just a guess because I only have experience with LHD RX8s. A RHD RX8 service manual should provide those details if you either have or can get one.

On a 6-port engine the APV barrels stick out about 150mm or so into the port cavity of the iron side plates. So Mazda says the engine has to come out because there isn’t enough space between the engine and the inner fender/frame rails to pull it out that far. Some people here on the forum say that if you lift the engine enough to take off the engine mounts and mount brackets, then push the engine far as you can to the LH side they just barely had enough room to take the 6-port LIM out and off the engine.

6-port LIM

https://cimg6.ibsrv.net/gimg/www.rx8...7f34bcab76.jpg


4-port LIM

https://cimg0.ibsrv.net/gimg/www.rx8...328702648b.jpg


So the 4-port engine LIM doesn’t have the APV/barrels. You should be able to unbolt it and lift it out without too much trouble as compared to the 6-port LIM I’d think. So now I’m thinking that you might not have to move the steering shaft out of the way.


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Well, I'll give it a go and report back!

You will need to pull it out an inch or two (3 - 6cm) for the Jet air nozzle extensions to clear. You can see the small tubes sticking out from the center ports on the manifold pic above.

A 192 4-port lower inlet gasket manifold gasket can be replaced without taking the engine out on a RHD car. Remove UIM & secondary air pump, disconnect fuel hoses and 2 injector plugs from LIM, Hang engine from crane. Remove LHS engine mount & bracket, remove RHS engine mount. Engine can be levered to LHS by about 4 cm, I used a wooden wedge between the mount bracket and the chassis to keep it there. Remove secondary air pipe (nuts usually blobs of rust which need heat). Undo LIM bolts and nuts, slide manifold across to clear studs x2 and jet air nozzles. Remove old gaske backwards and down between bellhousing and tunnel. Pass new manifold back in the same way - its a bit of a fiddle getting the jet nozzles and the studs through the holes in the gasket; care is needed not to bend/damage it. No need to touch the steering column or the brake servo.

Now sorted! Fingers crossed it stays that way. Correct gasket fitted and all reassembled. Brief warm up in the garage showed no codes and an STFT% of -3.5 / -4. Is this affected by premixing?

No, fuel trims will have almost nothing to do with premixing.

Ignore STFT until the coolant temperature reaches about 175°F (80°C).

Now running sweetly, all parameters within spec and no CEL.
Thanks for the help guys!

congrats, it's always a good feeling once you get something like this fixed and it solves everything.