2003 Yukon SLT still coding

[zmann96]

I've had a coding issue for 3 years now. 1074 - lean. back in 2017 it took 5000 miles to finally get a sticker after multiple tries. When it passed the guy said it's good but the coding will come back. Last year I never did get a sticker and just drove it hoping I wouldn't get stopped.
About 6 weeks ago I went and tried and it didn't pass so I have a rejection sticker good for 60 days.
this week I cleaned the MAF with cleaner and replaced all 4 - 02 sensors. I took it to pick up some items, filled it up when I left and again when I came back, I got 15.7mpg driving 70-80mph on highway 90% of the trip. I cleared the code and drove down no light came on, got my things and 2 miles down the road the light came on lean bank 2 ( 1074). this week I took the intake hose off while I was cleaning the MAF and put a glass bottle in the end and tightened it up and took a vacuum hose off the pump and pumped some air from my compressor, I had no air leaking that I could hear.
While I my way back I hooked up my scanner and looked at the live data. I noticed that the Short term trim on bank 2 was pegged at 25 and not moving longterm was not compensating into the negative was fluctuating between 13 and 16 on the plus side. I'm lost and I'm not a wiz with reading all the sensors and knowing what they mean as far as what's wrong. Over the past 3 years I've replaced all the coils, wires, MAF, MAP, both knock sensors, all the fuel injectors and recently the 02 sensors. would appreciate any help, not sure if I have access to any really good diagnostic shops up here in the Lake Region.

 

[zmann96]

One more thing, my friend mentioned my fuel filter which hasn't been changed but my question what ever it is it's only effecting bank 2. Could a bad cat cause a bad lean reading from that 02 sensor?

 

[treehan77]

Is the intake gasket leaking. You could do a test, using propane, carb cleaner, wd40, etc. spray it around the gasket while running. If it revs up a little, it’s leaking. I think this “extra air” coming after a lot of the sensors could explain your lean condition.

 

[zmann96]

Is the intake gasket leaking. You could do a test, using propane, carb cleaner, wd40, etc. spray it around the gasket while running. If it revs up a little, it’s leaking. I think this “extra air” coming after a lot of the sensors could explain your lean condition.

Yes, I've done the propane test and an air pressure test. But wouldn't a leak give me both a 1071 and 1074? not just one side?

 

[S33k3r]

Is your intake manifold plastic? I believe it is. THAT could be cracked, causing the issue on only one side. I have been told there is a TSB on the intake manifold cracking, but I couldn't quote it to you.

 

[zmann96]

Is your intake manifold plastic? I believe it is. THAT could be cracked, causing the issue on only one side. I have been told there is a TSB on the intake manifold cracking, but I couldn't quote it to you.

Gee, I did do a propane check all around the manifold and the RPMs never changed. I then put a bottle in the end of the intake hose and tightened it up and pumped some air in and didn't notice any leaking out. Thanks for reading my problem and responding, appreciated.

 

[S33k3r]

The only other thing I can suggest is finding a local tuner. They could likely better interpret the data you are getting, or get better. On top of that, you could likely get a custom tune... Is it possible that this is a computer and/or wiring issue?

 

[afpj]

Are your high fuel trims only at idle or does it go down when you hold steady at 2000 RPM? If it goes down that is a pretty good sign of a leak. If it stays high even at 2,000 RPM, we'll have to look at other issues such as fuel delivery etc etc

 

[zmann96]

The only other thing I can suggest is finding a local tuner. They could likely better interpret the data you are getting, or get better. On top of that, you could likely get a custom tune... Is it possible that this is a computer and/or wiring issue?

I tried a new computer and that didn't change anything so they took it back. I'm looking for a good shop with a good diagnostic machine.

 

[zmann96]

Are your high fuel trims only at idle or does it go down when you hold steady at 2000 RPM? If it goes down that is a pretty good sign of a leak. If it stays high even at 2,000 RPM, we'll have to look at other issues such as fuel delivery etc etc

Yes the bank 2 is pegged at 25 and no movement at any RPMS.