Chart 10

WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2010 Mercury Milan, 2010 Mercury Mariner, 2010 Mercury Grand Marquis, 2010 Lincoln Town Car, and 2010 Lincoln Navigator L. However, it is still accessible from the selected car via links, so may be relevant.

Poor Fuel Economy

NOTE: Driving styles may have a significant influence on fuel economy. Verify the concern before starting an in-depth diagnosis. If available, use the integrated diagnostic system (IDS) fuel economy test to verify a concern is present. The following external factors may contribute to poor fuel economy:

stop and go driving
incorrect tire pressure and size
vehicle loads (such as trailer towing)
extended winter warm-up conditions
high speed driving

incorrect axle ratio
road/weather conditions
aftermarket add-ons
short run operations
customer expectations

POOR FUEL ECONOMY SYMPTOM CHART

SYSTEM/COMPONENT	REFERENCE (article 5 Pinpoint Test unless noted)
Check the following PIDs: LONGFT1/LONGFT2 (value between -20 and +20%) VPWR (value between 10.5 and 17.0 volts, and within 0.5 volt of battery voltage)	LONGFT1/LONGFT2 value low (-): Continue diagnosis. Concentrate checks in areas that would cause the engine to run rich. LONGFT1/LONGFT2 value high (+): Continue diagnosis. Concentrate checks in areas that would cause the engine to run lean. VPWR not between 10.5 and 17.0 volts: REFER to the appropriate Charging System and carry out the Inspection and Verification to continue diagnosis. VPWR between 10.5 and 17.0 volts, but not within 0.5 volt of battery voltage: CHECK the B+ voltage to the PCM power relay. CHECK the VPWR circuit between the PCM and the PCM power relay. CHECK the PWR GND circuits.
Verify the engine operates at normal temperature.	Visual. REFER to the appropriate Engine Cooling, Symptom Chart to diagnose any cooling system concerns that are present.
Secondary Ignition System	For vehicles equipped with a coil pack ignition system, GO to PINPOINT TEST JC . For all others, GO to PINPOINT TEST JB .
Fuel System	GO to PINPOINT TEST HC .
Exhaust System	GO to PINPOINT TEST HF .
Variable Camshaft Timing (VCT) System	GO to PINPOINT TEST HK .
Transmission Fluid Level	Visual.
Automatic Transmission	REFER to the Diagnosis By Symptom in the appropriate Automatic Transmission/Transaxle to continue diagnosis.
Positive Crankcase Ventilation (PCV) System	GO to PINPOINT TEST HG .
Additional Checks: Correct PCM VID block information. Refer to FLASH ELECTRICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY (EEPROM) to carry out the Making Changes to the VID Block procedure. Brake drag Base engine concerns Incorrect PCV valve Contaminated MAF sensor Intake air system	REFER to the applicable Workshop information article.
Additional Testing	GO to PINPOINT TEST Z .