I recently had an issue on my '94 LT1 running rough. The exhaust smelled rich but the code from the scan tool indicated "Lean Condition on Right Bank."
Well, digging deeper, using the code reader to look at the engine parameters while the engine was running I saw very low millivolt readings on the right O2 sensor. It read 90 millivolts and didn't change much at all. The left O2 sensor was reading from 900 millivolts to around 100 millivolts. That is what it should be doing. It is measuring excess oxygen in the exhaust and the voltage it puts out goes back to the computer to allow the computer to adjust the fuel/air mixture by regulating the duration of the fuel injector pulse. (the longer the pulse the more fuel delivered)
A low voltage from the O2 sensor would tell the computer the mixture is lean because there is excess oxygen in the exhaust. The computer then increases the fuel by increasing the duration of the pulse to the fuel injectors. When the mixture is enriched to the point that there is more fuel than can combine with the air there will be no excess oxygen in the exhaust and the O2 voltage will go up. That in turn signals the computer to reduce the fuel delivered. The computer reads the voltage from the O2 sensors many times a second and adjusts the fuel delivered. This is the closed loop mode of operatoin.
I noticed that when the Check Engine Lamp would come on the car would run better. After a while of having the Check Engine Lamp on it would go out and the car would go back to running rough. I finally figured out when when the computer got the lean code the computer goes into open loop mode where it uses fixed settings for the fuel mixture. For instance, when you start the car cold, before the O2 sensors heat up and start giving good readings, the computer runs the engine open loop with preset mixture and timing settings. Once warmed up the computer "closes the loop" and starts regulating the mixture based on the O2 sensors measurement of excess oxygen in the exhaust stream.
In my case the low voltage from the failed O2 sensor told the computer the mixture was lean, so the computer increased the fuel delivered. But since the O2 sensor had failed it continued to indicate a lean mixture. At some point the computer decided that it couldn't deliver enough fuel to get a proper mixture on the right bank and turned on the Check Engine Lamp, dropped a code into the memory, and went into open loop mode.
So, you might want to take a look at the O2 sensor readings with a scan tool and see what they are.
Bob
Woodstock, GA
'94 LT1 Polo Green
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Bob - '94 Polo Green Coupe