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I’m going kinda crazy with this one, Chevy Cobalt 80psi at idle and after sitting for a while the 02 sensor goes flatline lean ( starts to run rough) very positive fuel trim numbers. Previous Mechanic swapped out plugs and 02 sensors( Denso) Should I swap the fuel pump since pressure regulator is inside fuel tank?
Conducted following tests
-smoke tested
-injector balance test
-exhaust back pressure tested
-current tested fuel pump (7Amps @ 7,300rpm)
- MAF and Map sensor ok
I think if my fuel gauge showed 80psi at idle, id try and grab another one and hook it up to make sure mine is accurate. I've heard of the pressure regulators faulting out causing high fuel pressure. You say the vehicle goes lean and runs rough with positive fuel trim numbers if it sits for a while, is the fuel pressure still 80psi during that?
BlackAir_86! wrote: I think if my fuel gauge showed 80psi at idle, id try and grab another one and hook it up to make sure mine is accurate.
Yeah I don't trust that gauge reading either. 7,300 rpm sounds too fast for a pump running at high pressure. And the PCM shouldn't be adding fuel if the pressure is high.......
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