So i own an 04 Mazda RX8 192ps, Rebuilt engine 12k Miles ago.

I have a full exhaust including a de-cat, which i've had on the car for at least 3 months before this happened.

It was running fine with no issues that i had known off, apart from a slight hesitation in power when going passed 6.5k rpm, the revs would rise as expected but it felt between 6.5k-6.8k it wouldn't make power then would kick back in, bit strange but barely noticeable.
Anyway one day on the way to work in stop start traffic at a set of lights it decided to cut out whilst idling. I was unable to get it going until someone gave me a push and managed to bump start. When it started it sounded very rough, to the point where i believe it was only running on one rotar all together after listening to videos online. I drove just enough to get off the busy road and it cut out between gear changes as the idle just rapidly dropped. Unable to start it again, even after trying to bump start i got it toed home.
Once home i checked the coils, leads and they work fine, and tried to see if anything once lose but everything seemed fine. So i tried using jump leads, and tried de flooding a few times and it sounded like it wanted to start but wouldn't. I removed the spark plugs and they was completely black like seen below, these were brand new plugs i replaced about a month before with the coils and leads. I swapped them for my old plugs i took out, connected jump leads and it started after some slight encouragement with the throttle. Although it started it didn't sound nearly as bad as it did before but there was a horrible repeated clicking noise coming from either the throttle body or further along where it splits into two intakes, hopefully you can hear it in the video below. I tried to see if it would move under its own power and it did but had to be kept alive with the throttle or it would choke it's self and stall (this time it would try to run but choke whereas before it would just straight die). It has no power and sounds terrible the higher up the revs it goes as if something is catching.

I manged to get hold of a obd scanner and the codes shown as below.

P0336 - Crank positioning sensor - This code had been coming on every now and then and i have replaced the crank sensor before and it still would randomly come on at its own will.
P0102 - MAF sensor - I checked the sensor and it seemed clean and normal
P0113 - Intake air temperature - no clue
P2096 - Post cat fuel trim too lean

I cleared the codes and the only one to come back consistently is the P2096.

What i think (Im slowly learning about this car so im probs just talking crap here)
I know in the intake there is a lower valve (SSV - no idea) where i think the noise is coming from, could it be that is stuck or not opening correctly, or is a sensor somewhere freaking it out but would it cause this kind of issue.

 

Unlikely an SSV problem, that doesn't really affect idle. Also, the black plugs show your car is running really rich. For P2096, you should have your exhaust system checked out. There is a leak in it somewhere near where the midpipe is by the O2 sensors. Also wouldn't hurt to have a compression test done to rule out the engine.

 

^^ ++
Agreed. also, would be nice to know what the car thinks it is doing. An ODBII reader and phone app that shows AFR would be grand.