I have this @!#$ problem that i cant resolve

the car run "good" until he go in close loop. the car idle fine but when i hit the gas and try a certain rpm , rpm go up and down and the air fuel ratio go way to lean to way to rich
if i unplug the o2 sensor it stop to doing that

last year the car was ruining good

but this winter I did some mod to the car

new custom fuel rail
crappy aem fuel regulator that don't hold any pressure
msd 2.2 coil swap
heated o2 sensor
chromed alternator

any suggestion ??



Location: Montreal, Quebec

i'd say the custom fuel rail and the regulator that don't hold pressure. the computer doesn't know how much fuel it needs since there is no pressure. its going crazy after dumping fuel then it thinks well thats to much fuel. put your stock stuff back on or get ones that hold pressure.

the fuel pressure drop only when I shut off the engine



Location: Montreal, Quebec

because it is off. the fuel pump aint pumping fuel.

when the fuel pump is pumping is causes pressure on the fuel system. since you put a fuel pressure regulator that you stated doesn't hold pressure i'm assuming its that or its not rail not sealed to the regulator or injectors