Poor Fuel Economy: Sensor/System
- Check for the following that may cause the engine to run rich:
- Any water intrusion in the HO2S connector.
- The engine oil contaminated by fuel.
- An EVAP canister purge condition.
- Incorrect fuel pressure. Go to FUEL PRESSURE TEST
under FUEL SYSTEMS (GASOLINE) in BASIC DIAGNOSTIC PROCEDURES - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE article.
- A leaking fuel pressure regulator. Go to FUEL SYSTEM DIAGNOSIS (GASOLINE)
under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE article.
- Any leaking fuel injectors. Go to FUEL SYSTEM DIAGNOSIS (GASOLINE)
under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE article.
- Any vacuum hoses that are split, kinked, or improperly connected.
- An air intake duct that is collapsed or restricted.
- An air filter that is dirty or restricted.
- Check the air intake system and crankcase for air leaks.
- Check for an Engine Coolant Temperature (ECT) sensor that has shifted in value. Go to TEMPERATURE VS. RESISTANCE
table.
- Check the crankcase ventilation system for proper operation.
- Check for an inaccurate speedometer.
- Use a scan tool to monitor the Knock Sensor (KS) system for excessive spark retard activity.