very high o2s

[matt87]

asking for a friend, hes running an me-r for 72s. he tells me the o2 reading are "stuck" in the high 900s. plugs are black carboned. was running fine then it just started a couple days ago . fuel reg messed up? chip problem? thanks for any tips!

 

[Squid4life]

Does he have a gauge on the fuel rail to read pressure? I know little to nothing about ME-R, but that is where I would start. What about MAF readings? (MAF could be getting lazy, should go to 255 on a scan tool) Vacuum leak?