my Toyota Highlander is getting terrible fuel economy, how can I improve it

Toyota Highlander Third Generation (2014-2019)

Error Codes

2-4 hours

Time

medium

Difficulty

medium

Severity

3 min read

509 words

Problem Statement

Learn how to diagnose and improve fuel economy issues in your Toyota Highlander. Step-by-step guide with diagnostic procedures and repair instructions.

Affected Component

Engine

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical systems.
•Allow the engine to cool before opening any engine components.

Symptoms

•Check engine light illuminated
•Noticeable decrease in miles per gallon (MPG)
•Engine stalling or rough idle
•Increased emissions from the exhaust
•Unusual engine noises during acceleration

Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to identify potential issues.
2
Check tire pressure and tread condition to ensure proper rolling resistance.
3
Inspect air filter for dirt or clogging that could restrict airflow.
4
Measure fuel pressure to ensure the fuel system is operating correctly.
5
Examine the condition of spark plugs and ignition system components.
6
Review the vehicle’s maintenance history for overdue services.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

Verification

After completing the repair, verify that the issue has been resolved:

✓Test the affected component to ensure it functions correctly
✓Check for any error codes or warning lights
✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

•Follow the manufacturer's recommended maintenance schedule
•Address warning signs early before they develop into major issues
•Use quality parts and fluids recommended for your vehicle
•Keep detailed records of all repairs and maintenance

Tools & Equipment Required

•OBD-II scanner
•Tire pressure gauge
•Spark plug socket
•Torque wrench
•Basic hand tools (screwdrivers, pliers)

Parts Required

•Air filter
•Spark plugs
•Fuel injector cleaner

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Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to identify potential issues.
2
Check tire pressure and tread condition to ensure proper rolling resistance.
3
Inspect air filter for dirt or clogging that could restrict airflow.
4
Measure fuel pressure to ensure the fuel system is operating correctly.
5
Examine the condition of spark plugs and ignition system components.
6
Review the vehicle’s maintenance history for overdue services.

Solution

1. Preparation

Gather necessary tools and parts.
Ensure the vehicle is parked on a level surface and the engine is off.
Allow the engine to cool before beginning any work.

2. Replace Air Filter

Locate the air filter housing, usually near the engine.
Open the housing by unclipping or unscrewing it.
Remove the old air filter and inspect for dirt or damage.
Install a new, clean air filter (refer to the owner's manual for the correct part number).
Secure the housing back in place.

3. Inspect and Replace Spark Plugs

Remove the ignition coil or spark plug wires (ensure you note their order).
Using a spark plug socket, remove the old spark plugs.
Inspect the old plugs for wear or fouling; replace with OEM or high-quality aftermarket plugs.
Torque the new spark plugs to the manufacturer’s specifications (typically around 13-15 lb-ft).
Reinstall the ignition coils or spark plug wires.

4. Tire Maintenance

Check tire pressure using a tire pressure gauge; inflate to the recommended PSI.
Inspect tire tread for uneven wear; consider rotating tires if necessary.
Replace tires if they are worn beyond safe limits.

5. Fuel System Cleaning

Add a fuel injector cleaner to a full tank of gas following the product instructions.
Consider having the fuel injectors cleaned professionally if they are clogged.