Exhaust Toyota IQ (2008-2014)

The Toyota iQ, a compact city car produced from 2008 to 2015, is known to experience several typical exhaust system issues :

• Persistent exhaust odour caused by a faulty lambda sensor affecting air-fuel mixture and engine running.
• Clacking noises from the exhaust, especially on the 1.33 VVT-i petrol engines, often due to worn mounts or fixings.
• Failures in the catalytic converter such as blockages or overheating, sometimes temporarily managed with a silicone additive but usually requiring replacement.
• Malfunctioning exhaust valves that cause noise or reduced engine performance, typically needing professional repair.
• Exhaust gases entering the cabin, possibly linked to clogged DPFs or cabin filters, which should be replaced to reduce emissions and clean interior air.

While the primary role of a silencer is to reduce the noise produced by the exhaust gases passing through the exhaust pipe, it also contributes to the overall exhaust engineering by managing back pressure. Proper back pressure is critical for maintaining engine power and torque, ensuring the vehicle runs smoothly and emissions are controlled effectively.

An exhaust leak can cause unusual sounds such as hissing or clattering and can affect engine performance by altering exhaust pressure and emissions readings. However, similar symptoms can also be caused by the engine running too lean or too rich — meaning the air-fuel mixture is incorrect due to sensor faults or other factors. It is important to check for leaks and verify sensor operation for accurate diagnostics.

Replacing the rear silencer involves the following steps :

• Lift the rear of the vehicle securely using a jack and stands.
• Remove the clamps and fixings connecting the silencer to the exhaust system.
• Install the new silencer and tighten the bolts to the manufacturer’s recommended torque.

This procedure is suitable for competent DIYers but may vary in cost and time depending on the workshop.

A faulty lambda sensor disrupts the air and fuel mix entering the engine, resulting in inefficient combustion. This typically produces a strong exhaust odour and can cause the engine to run roughly, impacting power and emissions negatively. Replacing the sensor usually restores correct engine running and reduces excess exhaust smell.

The catalytic converter in the Toyota iQ can suffer from blockages or overheating, affecting exhaust flow and emissions compliance.

Temporary solutions include adding a silicone additive (approximately 70 ml) to clean the catalytic converter internally, but this is not a permanent fix. In most cases, a replacement of the catalytic converter is necessary to ensure proper performance and compliance with emissions standards.

Exhaust gases can leak into the vehicle cabin typically due to faults in the DPF or a clogged cabin air filter. To reduce this problem and improve air quality inside the vehicle :

• Replace the Diesel Particulate Filter (DPF) if it is blocked.
• Change the cabin filter regularly to prevent infiltration of gases.

This maintenance helps limit emissions and produce cleaner air inside the car.

If you notice abnormal sounds like clacking or increased noise from the exhaust, or detect poor engine performance, it is important to check :

• The condition of mounts and fixings securing the exhaust system.
• Status and function of the lambda sensor and pressure sensors.
• The catalytic converter for blockage or damage.
• The functionality of exhaust valves or flaps which can affect sound and engine torque.

Prompt diagnostics using professional tools or services will help to identify faults and ensure your Toyota iQ’s exhaust system is properly fitted and running efficiently.

Maintaining the exhaust system in good condition is essential for emissions control, engine power, and optimal compression pressure.