Ask the Mechanic

Avoid questionable fuel stations to protect your catalytic converter

Hi Paul, my 2012 Toyota RAV4 has lost engine power, cannot accelerate. The exhaust has a foul smell and unusual excessive smoke. What could be the cause of this?

Mathew Busingye.

Hello Mathew, your Toyota RAV4 may have a damaged catalytic converter (also called CAT). This is a device installed in your exhaust system and designed to chemically render exhaust gases less harmful to the environment as they pass through the exhaust pipe from the engine. When the catalytic converter fails, you will experience, reduced (sluggish) engine performance and acceleration, the smell of sulphur or rotten eggs, unusual dark smoke, occasional rattling sound of broken down CAT components and unusually increased heat under the car.

Catalytic converters usually fail when they overheat, break into pieces or meltdown.

The usual causes of catalytic converter damage are: bad or adulterated fuel, incorrect engine timing and fuel mixture, leaking damaged fuel injectors, bad spark plugs or damaged oxygen sensors. 

These faulty components cause a rich fuel mixture (imbalanced fuel air ratio with more fuel).

The unburnt fuel is dumped on the red hot CAT which causes burning and CAT meltdown. At this point you need to replace the CAT.

You can prevent this situation by avoiding questionable fueling stations along highways, replacing worn out spark plugs and damaged oxygen sensors on time.

More causes.

The usual causes of catalytic converter damage are, bad or adulterated fuel, incorrect engine timing and fuel mixture, leaking damaged fuel injectors, bad spark plugs or damaged oxygen sensors.

The Forester XT boasts better spects than aTiguan R Line

I am looking at getting a stylish SUV that will do well on our roads but is also fast and stable on the high way. I am looking at either a 2010 Forester XT or a 2010 Tiguan R Line. Please advise. Thank you.

Daniel Twinomugisha.

Hello Daniel, the 2010 Subaru Forester XT and 2010 VW Tiguan R line are attractive compact cross-over utility vehicles. When comparing the Forester XT and Tiguan R, scales seem to tilt in favour of the Forester XT for all round superior performance, handling, practicality, cost of ownership and reliability. On the other hand, the Tiguan R puts up a spirited challenge with better fuel economy, superior dynamic driver assist and safety features, better exterior and interior styling, comfort and cabin furniture.

 Performance:

The Forester XT’s EJ25 2.5 litre turbo charged flat 4 engine delivers punchy 227 horse power or 259 horse power (for the XT Premium) which guarantee an adrenaline rush.

Forester’s suspension design, higher ground clearence and full time. All-wheel drive give it superior handling both on tarmac and the countryside dirt roads.

Tiguan’s 2.0 litre turbo feels less sprightly when you release the 197 horse power, however, it is a good car with better dynamic passive safety features (ABS/Brake assist) and superior fuel economy (13 km/litre) compared to Forester’s (11.9 km/litre). I have reservations about Forester’s ageing 4 speed automatic transmission which doesn’t match the Tiguan’s fuel efficient six speed automatic transmission.

Design and styling:

The VW Tiguan has better styling inside out. Forester’s plain plasticky cabin offers some comfort trappings such as blue tooth connectivity, six speaker surround and touch screen audio. However Tiguan is ahead of the Forester tech curve with better entertainment and comfort features as well as superior quality upholstery and in cabin materials.

Practicality, reliability and cost of ownership: Subaru Forester is more spacious offering better shoulder room, leg room, hip room as well as cargo volume. It also has better ground clearance for occasional visits to your garden during the weekend. The Forester is cheaper to acquire as well as maintain with more affordable and readily available parts.

Tiguan’s maintenance is pricy and most likely has costly 100,000 km fixes such as the water pump, timing chain kit ignition coils.

The Tiguan has a sensitive DSG gearbox which will fail if you don’t service it with special gearbox fluid and service kit. The choice is yours, You could take on the pricier VW Tiguan ownership and maintenance costs while enjoying its comfort and better fuel economy or opt for the faster, more practical and affordable Subaru Forester XT.

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