Poor Fuel Economy

POOR FUEL ECONOMY
Definition: Fuel economy, as measured by an actual road test, is noticeably lower than expected. Also, economy is noticeably lower than it was on this vehicle at one time, as previously shown by an actual road test.

IMPORTANT PRELIMINARY CHECKS
Before using this section you should have performed the "On-Board Diagnostic System Check" - Powertrain/On-Board Diagnostic System Check and determined that:
1. The control module and MIL (Service Engine Soon) are operating correctly.
2. There are no diagnostic trouble codes stored, or there is a diagnostic code but no MIL (Service Engine Soon).
^ Several of the following symptom procedures call for a careful visual/physical check. The importance of visual/physical checks cannot be over stressed. because they can lead to correcting a problem without further checks and can save valuable time.

VISUAL / PHYSICAL CHECK
This check should include:
^ Control module grounds for being clean, tight, and in their proper location.
^ Vacuum hoses for splits, kinks and proper connections, as shown on "Vehicle Emission Control Information" label Check thoroughly for any type of leak or restriction.
^ Air leaks at all mounting areas of the intake manifold sealing surfaces.
^ Ignition wires for cracking, hardness, proper routing, or carbon tracking.
^ Wiring for proper connections, pinches, and cuts.
^ The following symptom charts contain groups of possible causes for each symptom and cover several engines. These procedures are not necessarily meant to be done in consecutive order. If Tech 1 scan tool readings do not indicate the problems, then proceed in a logical order, easiest to check or most likely cause first. To determine if a particular system or component is used on a specific vehicle, refer to the "Electronic/Powertrain Control Module (ECM/PCM)" Wiring Diagrams for application. Electronic/Powertrain Control Module (ECM/PCM)

^ Check air cleaner element (filter) for dirt or being plugged and operation of thermostatic air cleaner.
^ Visually (physically) check: Vacuum hoses for splits, kinks, and proper connections as shown on "Vehicle Emission Control Information" label.
^ Perform "On-Board Diagnostic System Check." - Powertrain/On-Board Diagnostic System Check
^ Check owner's driving habits.
- Is A/C "ON" full time (Defroster mode "ON")?
- Are tires at correct pressure?
- Are excessively heavy loads being carried? Is acceleration too much, too often?
^ Suggest owner fill fuel tank and recheck fuel economy.
^ Suggest driver read "Important Facts on Fuel Economy" in Owner's Manual.

FUEL SYSTEM
^ CHECK: Fuel type, quality and alcohol content. Component Tests and General Diagnostics
^ CHECK: Fuel pressure. Refer to "CHART A-6". Related Tests, Information and Procedures

IGNITION SYSTEM
^ CHECK: Spark plugs. Remove spark plugs, check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Repair or replace as necessary.
^ CHECK: Ignition wires for cracking, hardness, and proper connections.
^ CHECK: KS system operation.
^ CHECK: Ignition timing. Ignition Timing

COOLING SYSTEM
^ CHECK: Engine coolant level.
^ CHECK: Engine thermostat for faulty part (always open) or for wrong heat range.

ADDITIONAL CHECKS
^ CHECK: Transmission shift pattern.
^ CHECK: TCC operation - A scan tool should indicate a RPM drop when the TCC is commanded "ON."
^ CHECK: For proper calibration of speedometer.
^ CHECK: For dragging brakes.