2004 Yukon Denali 6.0 AWD- HELP runs like my rav4

Hey guys, first post here. Don’t chew me out too bad if it’s just something easy and I have over looked. My Yukon will drive all day with no load, if and only if I stay under 25% throttle. If I give it more it stumbles. It won’t go above about 3500 rpm up or down hill doesn’t matter. It will do the same thing in park if you hold it to the floor.
I get, pending and current, Lean condition codes, bank 1 and bank 2.
Live stream shows fuel trims maxing out when I give it more than 25% throttle.
Absolute throttle position seems right on live stream.

What I have done;

New fuel pump and lines(pump->rail)
Confirmed 60 psi at idle and under throttle, not while driving

New air filter

New plugs and wires A/C-D
All 8 even the back 2

New down stream o2 sensors due to a cat efficiency code. Spacers solved that

New line for pvc valve. 2004 valve is in the valve cover, non serviceable.

Performed smoke test. No luck. No leak near intake. Or under hood.
There was smoke coming out of my vent valve near the charcoal canister. Idk if that was supposed to happen or not.

I had the classic abs buzz, 2 new abs sensors fixed that along with new calipers and all.

Also the hose from the pcv valve on valve cover to the intake whistles. If you pinch it, it will stop.

Let me know what you think. I am stumped.

@iamdub and @swathdiver might be good resources.

Please confirm, fuel trims ok at idle but are 25% positive on the throttle? Where did you get the plugs and wires from? Amazon? Or a reliable source like Rock Auto or dealer?

My RAV4 doesn't run like that at all Lol, although it definitely has more road noise than my 21 year older Yukon!

The downstream O2 sensor workaround is a clue that the cats might be plugged.

Gene456 said:

New down stream o2 sensors due to a cat efficiency code. Spacers solved that

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There's your problem. Replace the offending cat(s). Your symptoms describe a plugged cat.

New downstream sensors reporting cat efficiency problem. The PCM told you what was wrong. Next time get simple $30 IR thermometer and hit the front and backend of the Cats and you will see that the downstream end of the cats are much colder than the inlet side. Thats because they are plugged and not flowing enough exhaust out. Same symptom as Eddie Murphy stuffing a potatoe in your exhaust pipe.

rockola1971 said:

New downstream sensors reporting cat efficiency problem. The PCM told you what was wrong. Next time get simple $30 IR thermometer and hit the front and backend of the Cats and you will see that the downstream end of the cats are much colder than the inlet side. Thats because they are plugged and not flowing enough exhaust out. Same symptom as Eddie Murphy stuffing a potatoe in your exhaust pipe.

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Banana in the tail pipe. Thank you all for your advice. I will put the temp gun on the cats and see what I come up with.

afpj said:

Please confirm, fuel trims ok at idle but are 25% positive on the throttle? Where did you get the plugs and wires from? Amazon? Or a reliable source like Rock Auto or dealer?

My RAV4 doesn't run like that at all Lol, although it definitely has more road noise than my 21 year older Yukon!

Click to expand...

I just meant half cylinders. lol. Yes fuel trims are normal fluctuating regular. Then when it does its thing. Straight to 25% positive. I don’t remember where I bought the plugs. Mine fell off when I checked them. So these are better

Good morning all, this problem has been on going on and off still. This vehicle is my 3rd and a plow truck. So I usually don’t drive it. But I have been lately. After some digging around I found the coil pack on the first and last cylinder on bank 1 arcing out at night. So I ordered a set of coil packs and I believe that will do it.

Good evening everyone, the symptoms more or less went away for most of the summer and fall. All but an off and on random/multiple misfire code. I checked the coil packs. Found a few arching out. Replaced all 8 in the end. Problem still occurs. The other day the thing wouldn’t get out of its own way. So this time I had a fuel pressure gauge handy while it was acting up. I found the fuel pressure dropped to 10psi under heavy throttle. Along with about 50psi at idle. So tonight I replaced the fuel pump again. And while I was there I took care of the catalytic converters. Problem seems solved. I pulled it back in the garage after the initial test drive and replaced the intake gasket and oil pressure sensor due to the sensor failing along my journey. Now I believe I’m done working on this ride for a while. Hopefully. Thank you all for your feedback. Sorry it was a year in the making