System Too Lean
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 1993 Pontiac Bonneville, 1993 Oldsmobile Ninety-Eight, 1993 Oldsmobile Eighty-Eight, 1993 Buick Riviera, and 1993 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
If air/fuel ratio is too lean, idle speed may be either too high (check for vacuum leaks) or too low. Engine speed may vary up and down; disconnecting IAC may not help. Scan and/or digital voltmeter (10-megohm) will read an oxygen (O2) sensor output less than 300 mV (.3 volt). Check for low fuel pressure or water in fuel. A contaminated O2 sensor (caused by silicone) will produce lean air/fuel mixtures with an O2 sensor output fixed greater than 800 mV (.8 volt). This may also set Code 45.