Bone stock, auto. trans. with 140 K miles which displayed a generic code "P0171 System too Lean (Bank 1)" several weeks ago.
When the engine is cold, it's almost un-driveable, any acceleration results in a hesitation/bogging condition which almost kills the engine. Occasionally it will backfire just to let you know it's unhappy......... Cold idle is OK.
Once it warms up, the hesitation is less pronounced and only happens occasionally.
At times warm engine idle drops suddenly to barely 400-500 rpm, then correct itself.
Fuel pressure is normal, filter was just replaced.
I'm inclined to condemn the PCV valve, if I could only find it...........lol

Has anyone else experienced these symptoms?
Thanks in advance !

 

have you check the o2 sensor, this can cause a lean burn. and the idle control may need a clean up.