1994 Chevrolet Corvette • 53,000 miles

I have a 1994 C4 corvette with 53K miles that continues to post a 64 (lean O2) diag code. Replaced o2 sensor (2x), checked wire continuity to ECU and voltage @ sensor. Fuel pressure seems ok @ 41 lbs and injectors read 16.0- 16.5 ohms. Engine runs fine until operating temperature attained and then runs ruff under closed loop control while at idle. A lot of black smoke when run hard under closed loop control. Also BAD gas mileage and smell indicating rich mixture. New plugs and wires. All other parts and sensors are original.
September 6, 2011.

The computer is running the engine rich because of the lean mixture reading from the sensor. Check wiring to the sensor. Check for vacuum leaks on the engine that would allow more air into the system

Thx for the repy
I have been chasing this for 2 months now and have become quite frustrated (almost traded it in last week for a C6)!
--- I checked the wiring from the o2 sensor to the ECU - good continuity - performed shake and pull test on connectors - continuity still ok!
Can I use starting fluid (ether) for the vacuum test -- spraying around the vac hoses and manifold? Dont want to break what isnt broke!
Could this be an injector issue- partial clog or misfire causing lean condition? Wouldnt think so or it would show itself regardless of engine temp but I am an old points and condenser mechanic and dont know what I am talking about!

Sep 6, 2011.
It could be an injector issue. As far as the starting fluid, you may want to consider starting fluid. It works too but isn't quite as flamable. Whatever you do, have a fire extinguishier near by. If either hit a hot enough surface, it can ignite.