Have a Q60(g37) but figure the 370z forum is more active and the platforms similar enough ill post here.

2014 AWD Q60 - 42k miles
My car all of a sudden started having this issues, I am boosted working on getting E-tuned, my latest revision I did several logs/pulls and drove for a few days everything perfectly fine, tune was pretty close to dialed in.
Then randomly out of nowhere I go to do a 3rd gear pull and car has no power, shifts to 4th and then takes off like its back to normal. Then once I slow down and come to a stop, I start hearing an odd tapping sound, sounds like its coming from the back of the engine area (hard to pin point).

The noise is not present in neutral, only in gear only between about 1900-2500 rpm its almost like an on off switch hitting 1900 and exiting 2500. If I coast and have rpm drop down through that RPM range it doesn't do it. So only in gear underload while accelerating. The noise is pretty quite but without the radio on its noticeable. Besides the odd noise it drives good with good AFRs in certain scenarios like slight incline low throttle it might stumble or hesitate a little, but otherwise drives fine besides at WOT.

Now every time I do a pull its breaking up and backfiring, I managed to get a log of it and bank 1 is randomly going lean, looks like its only happening at higher RPM, as I didn't see this between 3k-5700 rpm.

Besides the supercharger nothing has really changed on the car in 2+ months of daily driving it with no issues, the supercharger has been daily driving about 2 weeks no issues, until randomly this issue popped up.

I have catless res downpipes, but stock header. header to DP gasket should be good, hard to tell header to block though but its untouched still oem stock, Z1 coilpacks, NGK stock spark plugs both about 2k miles on them, new downstream 02 sensors, ported upper and lower manifold. ID 1300CC injectors. Currently no CEL or DTC codes, and fuel pressure is good, have a fuel pressure and boost gauge independent of ecutek.
2 or so month ago I had injectors flow tested and leakdown tested and they where fine.

Car has always been on the richer side with trims pulling a little fuel typically at 85-95% or -5 to -15 not ideal but not terrible, Idle about -5 to -8, cruising 2500rpm is 0 to -5 but other scenarios like low RPM low load will swing it to -15 to -20, coasting downhill for example.

not sure if the odd tapping and the bank 1 lean are related or coincidental or what.

 

If the issue originated at the beginning of a WOT hit, and continues to occur during WOT hits, I'm leaning towards you have a vacuum leak somewhere post MAF.

You have plenty of pump and injector....Maybe do a smoke test and see if there's any leaks that developed? Did your tuner give any indication what the issue may be?

 

I am boosted, so it would be a vacuum leak at idle/low load/vacuum conditions, but a boost leak at WOT/boost conditions which I believe would result in a rich condition at WOT and lean condition at IDLE if that was the case. IDLE I am a little rich at like 92-95% or -5 to -8 combined STFT/LTFT I guess that's with auto climate control on probably -2 worse with it off.

I am hoping / leaning to maybe an exhaust leak at the header on bank 1 would trigger lean WOT in only 1 bank. That tapping noise is kind of concerning and doesn't really sound like an exhaust like although those sometimes can sound unexpectedly, but it doesn't do it in neutral so I'm not sure.

Maybe something with the cams or VVEL actuator something stuck in the valvetrain maybe? not sure how that would effect things also no CEL/DTC is odd.

Hoping its not something with the flexplate or torque converter, but dont think those would effect AFR at WOT, maybe the WOT AFR and the tapping are not related.

 

Yea, the no CEL is puzzling to me and the fact you flow tested all your injectors, have enough pump, new coils/plugs and new O2s is odd. Maybe switch the O2 and see if it follows banks?

I have no idea what the ticking could be unfortunately. Pop the cover off and do a visual inspections?