"03 Cavalier 2.2L P0172 code "running rich"---tried everything

Question

2003 Cavalier 2.2L "Eco-Tech" been running *great for the last 5 years. 160,000 miles.  P0172 code "running rich" *suddenly pops up. Found leaking fuel pressure regulator (weeping gas from vacuum diaphragm nipple) **Thought "for sure" IT was the root of problem--replaced regulator (*wasn't the root) *car ran just the same. Cleared fault code several times, P0172 keeps coming back. Checked all parameters in "real time" (idling & driving) everything looks normal except "fuel trims" keep running "negative" compensating for the over-rich condition while driving. Removed and checked fuel evaporator canister for saturation--"dry as a bone", "purge" valves appear to be operating normally. Checked manifold vacuum with "mechanical" vacuum gauge against MAP sensor readback--both tracking exactly the same. Idle vacuum @ approx. 18"+. Load at idle around 33%+/-.  Both O2 sensors appear to be operating normally. Removed and cleaned IAC, checked TPS (in and out of vehicle)--OK. Air inlet temperature is registering normal. Engine temperature sensor is tracking normal (around 195-200F) Replaced air filter as "rule out". Replaced MAP sensor as "rule out". **Only "truly defective" component found was the leaking fuel pressure regulator which was replaced and then code erased. Drove car several miles P0172 "running rich" code came back. Cleared P0172 code "several" times, keeps coming back as "running rich". Car seems a little down and sluggish on power *as would be expected "running rich".  Idles "smooth as glass". Drives "smooth as glass"--no "missing" noted.  After clearing the code the car idles (normal) @ approx. 650 rpm. As fuel trim errors start adding up, the idle increases to around 900+ rpm, shortly thereafter the "check engine" light pops on with the same "running rich" code. I'm at WHITS END! ANY advice??? (besides junking the car)

Answer 1

P0172 Fuel trim rich Bank 1

If the catalytic gets partially plugged it will cause the engine to go rich, this make you may be able to separate the exhaust to the catalytic convertor and recheck the fuel trim