P0131 among other things...

[YukonXLGuy]

Alright guys, curiosity overcame my laziness and im back to working on the yukon. so i replaced the o2 sensors again with new bosch ones. its no longer throwing any codes and while in neutral runs great! the heavy rich smell from the exhaust is gone so she is finally fueling as it should. however it was acting down right stupid during my test drive again. 

 

Acceleration is non existent unless i floor it. it will accelerate slowing, eventually reaching 5500 rpm where it will hang for a few seconds, then bang into second. second is lethargic as well everywhere in that gear. once it gets into 4th gear and tc lock up it starts shuddering like mad. all of this is now leading me towards the transmission having issues. im still reading and researching the diagnosis portion of it all but figure you guys might have some faster, more pinpoint insight for me. appreciate everything you all have done for me thus far in taking care of this pig's issues!!!

[sefiroxx]

Shifting into 2nd at 5500? Need a scanner that will show tranny info, normally, 2nd committees at 3-3500. A scanner will help tell if it was commanded at 3 or at 55. If 3, then a tranny problem, if 55, then engine sensor problem. The computer uses data from rpm, speed, current gear, desired speed (tps) to determine when to shift.

Low o2 voltage signifies a lean condition. If at 0v, then the wire harness may be broken. Use a scanner to read o2 voltage to determine what voltage is at and whether it moves, if no movement then wire problem.

Your symptom also sounds like clogged exhaust. Could be cat or muffler. Downstream o2 sensor readings can help with diagnosis. You might want to remove the o2 sensors and take a quick test drive, it works better, then clogged.

AC Delco is now a rebranding parts distributor. No longer a safe option.