Diagnostic Aids

WARNING: This page is about a different car, the 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.

Fuel contamination, such as water, will affect the fuel trim.
The system will go rich if the injectors are supplying too much fuel.
Using the scan tool, review the Failure Records. If intermittent condition is suspected, see INTERMITTENTS in TROUBLE SHOOTING - 2.2L CAVALIER - BI-FUEL - CNG/GASOLINE article.