Having Issues Tracking Down A Problem

[200sxRb20]

ok guys, Ive been working on this for a couple weeks now(dont have much time thanks to the us army..) and am having abit of trouble tracking down this fuel issue. the engine is an rb20det from a cefiro. seems to be having a fuel issue. the old saying too much is never enough is apparently not true here. usually at low rpms, it bogs down, with black smoke and horrible fuel mileage. Ive replaced the fuel filter, FPR, checked fuel pressure, replaced plugs gapped properly, cleaned the maf, checked for intercooler leaks and vacuum leaks and couldnt seem to find any. I searched here and found some people with some of the same issues and the solution was to clean up the aac. I did that and it seemed to help alittle(it doesnt buck hard like it used to now). but it still shoots out black smoke every now and then(mostly at low rpms as mentioned) Power is lacking as well obviously. shooting flames when I downshift as well, which looks slightly cool, but obviously not supposed to do that.

now the only things i can thing of that are left is maybe a faulty fuel injector(maybe sticking open?) or the maf has just completely crapped out on me. when you unplug the maf and start the car, it runs idles even worse, and when connected, it idles better so im not sure if the maf is bad or not. i have yet to hook up a 12v sourse and and hook up a volt meter and see what output is. sorry for the long post Im just trying to be as detailed as possible. here are my mods if this helps. any help is greatly appricated.

RB20DET(from A31 Cerfio if i remember correctly)

ARP Head Studs,

GReddy 1.2mm Head Gasket,

GReddy Timing belt,

Fidanza adjustable cam gears,

Hybrid FMIC and piping,

Turbo XS BOV,

HKS pod filter,

3" exhaust with Fujitsubo NGK axle back,

GTR fuel pump,

Koyo radiator w/ dual 12" fans,

GReddy EManage,

GReddy Profec E-01,

GReddy Auto Timer,

[BH_SLO32]

Have you tried disconnecting the O2 sensor and seeing if the idle stabilises?

My initial thought was fouled plugs but you mentioned they have been replaced.

Cheers

[200sxRb20]

I will try unplugging the 02 sensor today and see how that works out for me. thanks for the reply mate

[200sxRb20]

unplugged the 02 sensor, didnt seem to make any differance in the idle at all. bad 02 sensor?

[BH_SLO32]

unplugged the 02 sensor, didnt seem to make any differance in the idle at all. bad 02 sensor?

No, usually when the O2 sensor plays up it results in an erratic idle (hunting) but stabilises once the O2 sensor is disconnected (presumably no longer in closed loop mode).

Have you inspected the plugs and are they all the same (presumably very black)? Usually fouled plugs will eventually clear themselves especially after a long run (eg down the highway).

[Syphon]

Maybe check ECU for fault codes if you haven't already

Also worth checking TPS is functioning correctly.

[blind_elk]

Have you checked ignition timing, both "base" and in the maps in the ECU?