why is my Toyota Highlander Third Generation (2014-2019) getting worse gas mileage

Toyota Highlander Third Generation (2014-2019)

Error Codes

2-4 hours

Time

medium

Difficulty

medium

Severity

3 min read

539 words

Problem Statement

Learn how to diagnose and fix decreased fuel economy in Toyota Highlander 2014-2019. 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 draining oil or working near hot components.

Symptoms

•Check engine light illuminated
•Noticeable decrease in miles per gallon (MPG)
•Engine stalling or rough idling
•Increased exhaust emissions
•Unusual engine noises (e.g., knocking or pinging)
•Fuel odor near the vehicle

Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to identify any underlying issues.
2
Check tire pressure and tread condition; under-inflated or worn tires can affect fuel economy.
3
Inspect the air filter for clogs or excessive dirt, as a blocked air filter can restrict airflow.
4
Examine fuel injectors for clogs or leaks that may disrupt fuel delivery.
5
Assess the fuel system for leaks or issues, including checking fuel pressure.
6
Review the engine oil level and condition; old or low oil can impact engine performance.

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
•Socket set
•Oil filter wrench
•Fuel injector cleaning kit

Parts Required

•Air filter
•Fuel injector cleaner
•Engine oil
•Oil filter

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Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to identify any underlying issues.
2
Check tire pressure and tread condition; under-inflated or worn tires can affect fuel economy.
3
Inspect the air filter for clogs or excessive dirt, as a blocked air filter can restrict airflow.
4
Examine fuel injectors for clogs or leaks that may disrupt fuel delivery.
5
Assess the fuel system for leaks or issues, including checking fuel pressure.
6
Review the engine oil level and condition; old or low oil can impact engine performance.

Solution

1. Preparation

Gather tools and parts necessary for the repair.
Disconnect the battery to ensure safety while working on electrical components.

2. Replace Air Filter

Remove the air filter cover using a socket set.
Take out the old air filter and inspect for dirt and damage.
Install a new air filter, ensuring it is seated properly.
Reattach the air filter cover and secure it with the screws.

3. Clean Fuel Injectors

Use a fuel injector cleaning kit.
Follow the instructions on the kit to connect it to the fuel rail.
Run the engine as instructed to allow the cleaner to flow through the injectors.
Disconnect the kit and ensure all connections are secure.

4. Check and Adjust Tire Pressure

Use a tire pressure gauge to check each tire’s pressure.
Inflate tires to the manufacturer’s recommended PSI (found on the driver’s door jamb).
Inspect tire tread and replace tires if they are excessively worn.

5. Change Engine Oil and Filter

Drain the old engine oil using a wrench to remove the drain plug.
Replace the oil filter using an oil filter wrench.
Reinstall the drain plug and refill the engine with the manufacturer-recommended oil type.
Run the engine briefly, check for leaks, and ensure proper oil level.