NEED HELP. Causes for running lean?

[hidesertwheelin]

So according to a lambada(sp?) calculator, my Suburban is running lean. My smog guy says that is the reason it will not pass smog. I am getting 10.5 psi after the fuel filter, and my O2 sensor is only a few months old. What else can cause a lean issue? I am going to replace my O2 sensor w/ a GM unit, since they only cost around $30. What else do I need to check.

 

[dyeager535]

You don't have enough pressure after the fuel filter IMO. Needs to be up around 13 on a stock setup, you might have a weak pump, bad hose in the tank, or simply bad filter.

 

[4xcrazy]

You don't have enough pressure after the fuel filter IMO. Needs to be up around 13 on a stock setup, you might have a weak pump, bad hose in the tank, or simply bad filter.

ditto,

went through all this crap a few years back with mine, kept throwing the O2 sensor code, reading lean condition.

replaced fuel pump, never had a problem after.

 

[hidesertwheelin]

ditto,

went through all this crap a few years back with mine, kept throwing the O2 sensor code, reading lean condition.

replaced fuel pump, never had a problem after.

I'm not throwing any codes though



As far as PSI, I thought anything between 9-13 was fine?

 

[4xcrazy]

I'm not throwing any codes though



As far as PSI, I thought anything between 9-13 was fine?

maybe you aren't driving yours the way i did

try "gettin on it" a few times, it SHOULD be lacking in " get-up-n-go" type power.

maybe the C.E.L. is burnt out,,,not sure.

 

[hidesertwheelin]

maybe you aren't driving yours the way i did

try "gettin on it" a few times, it SHOULD be lacking in " get-up-n-go" type power.

maybe the C.E.L. is burnt out,,,not sure.

The check engine light works... I got the standard code 12.

 

[dyeager535]

When are you seeing a lean condition? The computer can't compensate for differences in fuel pressure directly, because it "assumes" that it's receiving the stock amount of fuel, and doesn't know what the pressure actually is. Pressure lower or higher means less or more fuel getting to the engine than the computer thinks. Up to a point it can compensate for this by injector pulsewidth, but when fuel demand is higher (acceleration, under load), fuel pressure is going to play a much larger role, and at some point, the computer cannot compensate any further.

 

[hidesertwheelin]

When are you seeing a lean condition? The computer can't compensate for differences in fuel pressure directly, because it "assumes" that it's receiving the stock amount of fuel, and doesn't know what the pressure actually is. Pressure lower or higher means less or more fuel getting to the engine than the computer thinks. Up to a point it can compensate for this by injector pulsewidth, but when fuel demand is higher (acceleration, under load), fuel pressure is going to play a much larger role, and at some point, the computer cannot compensate any further.

Hummm.....I am failing on the 25 mph test on the dyno.

 

[dyeager535]

What are you getting before the filter for PSI?