2002 Aerio with p0171 code -engine running lean
On cold starts especially cooler or cold mornings, the car is sluggish after starting. It takes a few minutes for this to clear. It accelerates slowly and does not run better until warmed up or at higher speeds.
Running at 2k+ revs it is fine and does not miss or stutter. Acceleration is okay. But when slowing for lights or stops, revs drop usually to sub 600 and the car will stall. This happens too when attempting to accelerate from a stop at a light. Tapping throttle usually stabilized it. Hard acceleration from the near stalling state gives some backfire (?) sounds
I have cleaned out the EGR valve, inspected IAC valve, replaced PCV, replaced two short hose tubings between header and throttle body and cleaned the mounting holes, checked visually and audibly for intake leaks, inspected both o2 sensors, spark plugs replaced last year, visual inspection of exhaust (engine not running) showed no leaks or breaks...
Multimeter tests of EGR and IAC are normal, as did both o2 sensors.
This problem is consistent and persistent. Had different problems last year and had serious, heavy, black soot from exhaust once or twice on start up after repairs but never since. Did the EGR cleaning after this.
Any thoughts or suggestions would be appreciated.