Stagea S2 RS Four S Misfire/Rough Idle

[deev236]

Hi All,

First post here, hoping someone can help me with an issue that seems to come up a lot with RB25 NEO Skylines & Stageas but without any clear solutions (I've read through about 20 threads at this point on SAU).

So, seemingly a common issue - my Stagea is misfiring while at idle, with a pretty frequent backfire as well but no other noticeable misfires or problems when driving around/under load. 

The misfire has presented basically as a small dip in RPM's every few seconds while idling, minor but consistent. It's significant enough to feel the car vibrate every time it momentarily drops down by around 50-80RPM before it pops back up again to around 800RPM.

I've replaced the Ignition coils with Splitfires, new spark plugs gapped to 0.8mm, new O2 sensor and new MAF sensor after ECU diagnostic has shown error codes relating to Primary ignition, O2 sensor and MAF.

Something that I found strange was that when the MAF/AFM is unplugged, the idle does seem to smooth out. This is why I replaced the MAF/AFM but it seems like it's not the cause of the issue.

Next step I guess would be a flow test and possible replacement of injectors, but I'm wondering if anyone else has had this experience and if they solved it, what the solution was for them. 

Appreciate everyone reading through, I have done very extensive research online to try and fix this issue but haven't really gotten anywhere.

Cheers!

[GTSBoy]

The loom and its plugs.

[deev236]

Do you mean the Ignition Coil Pack Loom?

[GTSBoy]

Yeah, and the AFM, and the injectors.

[deev236]

Cheers man, just ordered the ignition coil loom will see how that goes. the AFM loom connector looks pretty old and crusty so might have a go at repinning a new connector and checking the wires. just gotta work through everything until I find the issue I guess!

[deev236]

Okay so I replaced the ignition coil loom with no luck. Took the car for a test drive around the block and it sputtered a bit in the lower revs and continued to idle rough when I stopped. 
 

Any other ideas? I'm guessing I'll have to look at the injectors next.

[Stick180]

Checked for vacuum leaks?