* Oxygen Sensor(s): A faulty oxygen sensor prevents the engine from getting the correct air/fuel mixture. This is a very common cause of poor fuel economy. They degrade over time and 13,000 miles is long enough for one to fail.
* Mass Airflow Sensor (MAF): This sensor measures the amount of air entering the engine. A dirty or faulty MAF sensor will lead to an incorrect fuel mixture, resulting in poor fuel economy and potentially rough running.
* Throttle Position Sensor (TPS): This sensor tells the computer the throttle's position. A faulty TPS can cause the engine to run rich (too much fuel).
* Vacuum Leaks: Leaks in vacuum lines can disrupt the air/fuel mixture, causing the engine to run inefficiently and consume more fuel. These are often difficult to find.
* Fuel Injectors: Clogged or faulty fuel injectors can spray an incorrect amount of fuel, leading to poor fuel economy.
* Spark Plugs (despite recent tune-up): While you mentioned a recent tune-up, it's possible the spark plugs are already failing or were of inferior quality.
* Transmission Issues: A slipping or malfunctioning transmission can cause the engine to work harder and consume more fuel.
* Air Filter: A clogged air filter restricts airflow, forcing the engine to work harder and use more fuel. Even if it was changed at the tune-up, it's worth checking again.
* Tire Pressure: Underinflated tires increase rolling resistance, leading to lower fuel efficiency.
* Driving Habits: Aggressive driving (rapid acceleration, hard braking) significantly impacts fuel economy.
What to do:
1. Check the obvious: Start with the easiest things to check: tire pressure, air filter.
2. OBD-II Scan: Take your van to an auto parts store (like AutoZone or Advance Auto) and have them perform a free OBD-II scan. This will check for any diagnostic trouble codes (DTCs) stored in the car's computer, which can pinpoint potential problems.
3. Professional Inspection: Based on the OBD-II scan results, or if no codes are found, take your van to a trusted mechanic for a thorough inspection focusing on the components listed above. They have the tools and experience to diagnose the issue accurately.
Don't just guess at the problem – a proper diagnosis is crucial to fixing the excessive fuel consumption effectively.
