Diagnostic Aids
WARNING: This page is about a different car, the 2002 GMC Sonoma and 2002 Chevrolet S10 Pickup. However, it is still accessible from the selected car via links, so may be relevant.
Fuel contamination, such as water and alcohol will affect fuel trim. The system will go rich if injectors are supplying too much fuel.
Review the Failure Records with a scan tool. If intermittent condition is suspected, refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.