skyline misfire

[evoboy88]

ok, so a buddy of mine brougth his 98 skyline gts-t to our shop because it has a misfire during acceleration with more than .2 bar boost, the car ran fine at 1 bar for more than six months then all of a sudden at wot and part throttle(more than .2 bar) it misfires, stumbles doesnt want to accelerate, any suggestions?

[themadscientist]

First thing I check in a misfire situation is ignition, plugs and coilpacks.

[evoboy88]

well i pulledc the cylinder #1 plug and it is quite brown, not damp but brown like someone rubbed it in the dirt, no white at all, at part throttle cruise he also says there is an occasional misfire that can be felt/heard. also at the time that the car was running ok, the factory boost selinoid was disconnected and the car was running 1 bar tuned on an S-afc and there is also no boost controller... the afc has been zeroed out and the factory selinoid reconnected, ecu reset, the car still has an occasional stumble and misfire, currently it runs at .5 bar, also could an 02 sensor code have anything to do with this, another friend says they shut off at WOT but i disagree.. thanks again

Chris