Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSFORD1990RANGER 4WD L4-140 2.3L SOHCREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTEMISSION CONTROL SYSTEMSTESTING AND INSPECTIONSYMPTOM RELATED DIAGNOSTIC PROCEDURESPOOR FUEL ECONOMY
1990 Ford Ranger 4WD L4-140 2.3L SOHC
Poor Fuel Economy
1990 Ford Ranger 4WD L4-140 2.3L SOHCSECTION Poor Fuel Economy
Fuel economy is noticeably lower than expected. Customer should drive vehicle and note miles per gallon decrease.
POSSIBLE CAUSE ACTION
EGR malfunction, Check EGR system in "Testing
Flange gasket leaking, Procedures" in Emissions
solenoid and thermo valves
malfunctioning
Ignition timing Check Ignition Timing in "Adjustment
Procedures" in Emissions
Spark timing Check Spark Controls (EST, ESC) in
"Testing Procedures" in Emissions
Air management valves Check Air Injection system in
"Testing Procedures" in Emissions
Air damper door binding, Check inlet air temperature system (TAC)
air cleaner temperature in "Testing Procedures" in Emission
control malfunction
Restricted exhaust Check Catalytic Converter in
"Testing Procedures" in Emissions
RENDER: 1.0x
NO RELATED
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Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.