2003 Yukon SLT scanner live status problems

[afpj]

Uh, still think you're fuel pressure.might be a little low...40 KOEO. You said you replaced O2 sensors...what brand? check the wiring to those? Did you see a graph of the sensor voltages to see if precats are cycling? O2 sensors can get lazy well before throwing a sensor code. Just some thoughts.

 

[zmann96]

Uh, still think you're fuel pressure.might be a little low...40 KOEO. You said you replaced O2 sensors...what brand? check the wiring to those? Did you see a graph of the sensor voltages to see if precats are cycling? O2 sensors can get lazy well before throwing a sensor code. Just some thoughts.

The sensors are only a month old and after replaced didn't change a thing. I don't have the equipment to do a graph. I am going to get a frequency testor and check my MAF it's frequency not voltage. I have it down I think to either too much air reported or not enough fuel. I believe at idle and 2500 and 3000 rpms the pressure is good. Thank for helping.

 

[Scottydoggs]

The sensors are only a month old and after replaced didn't change a thing. I don't have the equipment to do a graph. I am going to get a frequency testor and check my MAF it's frequency not voltage. I have it down I think to either too much air reported or not enough fuel. I believe at idle and 2500 and 3000 rpms the pressure is good. Thank for helping.

your really fighting not doing that fuel pump i see. new parts can and do fail all the time sadly. get/rent another f/p tester, the test is key to run, then fire it up, needs like 60 ish to run, the bleed off time after you turn it off means nothing at all. if you can get one with a long hose, run the gauge up to the windshield so you can see while driving, and drive it. if its 40 psi. get another pump.

 

[zmann96]

your really fighting not doing that fuel pump i see. new parts can and do fail all the time sadly. get/rent another f/p tester, the test is key to run, then fire it up, needs like 60 ish to run, the bleed off time after you turn it off means nothing at all. if you can get one with a long hose, run the gauge up to the windshield so you can see while driving, and drive it. if its 40 psi. get another pump.

Maybe I'm missing something. It was 40psi with key on engine not running. at 530rpms it was 59 psi, at 2500 and 3500 it was 57. I was told that was OK?? do you really think it's the fuel pump, I'm not opposed to getting another fuel pump just tired of throwing money for stuff that isn't it.

 

[Scottydoggs]

Maybe I'm missing something. It was 40psi with key on engine not running. at 530rpms it was 59 psi, at 2500 and 3500 it was 57. I was told that was OK?? do you really think it's the fuel pump, I'm not opposed to getting another fuel pump just tired of throwing money for stuff that isn't it.

pretty sure you need more then 40 at idle. id drive around and see if its jumping up and down, or just drops when under load.

 

[TJ Baker]

Any thoughts on exhaust leaks allowing air (oxygen) into the exhaust causing a false lean condition seen by the O2 sensor(s)?

 

[zmann96]

pretty sure you need more then 40 at idle. id drive around and see if its jumping up and down, or just drops when under load.

Ok, I'll try that. Thanks for sharing this and helping.

 

[zmann96]

Any thoughts on exhaust leaks allowing air (oxygen) into the exhaust causing a false lean condition seen by the O2 sensor(s)?

Funny you say that, I was talking to my son yesterday and we were talking about that. I figured I would hear an exhaust leak and he said maybe if it was just enough to leak but not leaking enough to hear it. I'm going to try some water and see if I get white smoke. Thanks for sharing and helping out.

 

[zmann96]

I think I found it. I hooked up a blower to my exhaust pipe and got a bottle of soapy water. I turned on the blower and I didn't need the soap I head the leak. this was bank 2 the worst fuel trims. I went of B1 side didn't heard anything but sprayed a block off plug on the exhaust manifold and it slightly bubbled B1 trims were better so all this makes sense. I had changed the manifolds 4 years ago with the common issue of broken off exhaust header bolts. the manifold I purchased had a block off plate for another application. both are leaking B2 more than bank one. should be an easy fix ??? I'll let you know how I make out. BTW I never heard and hissing or exhaust noise from either.

 

[zmann96]

Here's the worst side. It burnt out the gasket. That hole was filled with remains of gaskets, it' s a 1/2" hole. The plate looks like it has a hole but that's the gasket. I flipped the plate around after sanding off the rust, filled hole with ultra high heat JB Weld and put it back on. It has to cure before I try but i'm pretty sure it's got it.