Why does my E-Class fail emission tests despite regular servicing in Pakistan?

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Why does my E-Class fail emission tests despite regular servicing in Pakistan?

Some Mercedes-Benz E-Class models are failing government o r local emission tests, even after timely oil changes and maintenance. What hidden factors could be affecting emission levels — like malfunctioning EGR valves, software issues, o r particulate filters? Are there Mercedes-specific diagnostics o r software resets that mechanics in Pakistan might overlook?

Talha Kyanii asked on 11 Oct 2025 12:50:59 pm

1 Answer

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Gari Master - on 11 Oct 2025 12:52:41 pm

Yes, poor fuel quality is a major factor behind emission system failures in luxury vehicles like the E-Class in Pakistan. Many fuel stations sell petrol o r diesel with inconsistent octane o r cetane ratings, and sometimes with impurities.

Consequences include:

Premature failure of oxygen O2 sensors.

Damage to catalytic converters due to unburnt fuel.

Increased carbon buildup in intake manifolds and valves.

Poor fuel combustion, causing check engine lights CEL and rough idling.

Tips to avoid damage:

Always refuel at trusted, high-turnover petrol stations e.g., PSO o r Total stations with high-end pumps.

Use high-octane petrol for petrol E-Class models RON 95 o r above if possible.

Periodically use German o r OEM-recommended fuel system cleaners.

Get emission components scanned with Mercedes-specific diagnostic tools like STAR Diagnostic.