Ask the Mechanic: Why are my engine revolutions not stable?

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Hello Paul, I delayed servicing my manual first generation RAV4 by 300kms but whenever I start the engine, revolutions do not stabilise normally and it fails to reach 1,000 rpm. I have done the normal service and changed spark plugs but no change but the problem still persists. Please advise.


Hello Paul, if your first generation Toyota RAV4 experiences unstable engine idling and fails to reach 1,000 rpm (revolutions per minute) after you delayed servicing, it you may need a mechanic to perform an inspection. The throttle body and attached idle air control valve are critical for managing air intake which is crucial for performance, acceleration or consistent idle running.

The throttle valve can accumulate carbon or dirt deposits (from delayed air filter change) and the idle air control valve develop corrosion (from old engine coolant) which affects air fuel ratios and stable engine idle run. Inspect the air intake tunnel between the air cleaner and throttle unit for leaks.

Also, inspect the positive crankcase ventilation valve (PCV) which may be blocked by sludge from old engine oil. The PCV helps to release accumulated combustive gases usually re-channelled to help stabilise engine idle run. Engine management sensors such as the mass air flow and coolant temperature sensors can be critical in providing information that helps the engine computer to adjust engine idle accordingly.


Hello Paul, I am due to have a baby soon but I am worried about keeping them safe while in my car. What should I be looking for when choosing a car seat?


Hello Victoria, what you probably mean is the child safety seat also called a child car seat, booster seat or child restraint seat. This special seat is designed to protect children from death during vehicle collisions. Although these seats are usually bought by car owners, car manufacturers design their cars with suitable seat anchors and seat belts to accommodate child seats.

When buying a child car seat, you need to confirm that it is the appropriate one. For example, for infants it should be rear facing while older children need the convertible or booster seat. The child car seat should fit well on your car’s child seat anchoring points and seat belt design. You should choose a car seat which is not complicated to fit or use, easy to adjust harnesses or remove.

The car seat you select should also be designed with ample padding and support for child comfort. Go online and look at the different options of child safety seats and recommendations of types suitable for your car model.

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Hello Paul, I would like to buy an SUV for my wife similar in size to the Nissan Qashqai. I have not gone to physically look at cars yet but have checked online over the last few months and the Nissan Qashqai seems to be in that price range, depending on the model you go for. What has discouraged me is that the Nissan and a few others of this size all have continuously variable transmissions. Being old-school, the idea of a one-speed auto does not sit well with me. Can you please explain this to me and if they are okay?


Hello Christopher, the Continuously Variable Transmission (CVT) does not shift in steps (fixed gear ratios) as the traditional automatic transmissions (gearboxes). As such, it takes a little getting used to, especially for the performance leaning and impatient drivers. The CVT transmissions are popular worldwide because they provide a seamless range of gear ratios which give the motorist peak performance, smooth acceleration and superior fuel economy.

This appeals to the modern drivers who are often held up in city traffic jam as they go to shop, school drop offs or morning commutes to the office. With a little practice or reorienting to the CVT transmission, one can learn to enjoy the performance and fuel economy benefits. There have been concerns about potential failure of the used car CVT transmissions.

However, you can counter this problem by making sure you service the used car’s CVT transmission with the correct CVT fluid as soon as you take delivery. Servicing a CVT transmission or gearbox with Automatic Transmission Fluid (ATF) or not servicing it at all when it is due will damage them prematurely.

If your preference is the used Nissan Qashqai, go ahead and buy it so that you enjoy the outlined benefits of CVT transmissions.


Hello Paul, I would like to buy a car for my mother who is in her late 60s and retired. The vehicle will be mostly used for driving to the shops and the occasional school pick-up. She prefers the SUV type or hatch. What would you recommend?


Hello David, it would be important to bear in mind your mother’s preference for an SUV (Sports Utility Vehicle) and the intended usage, that is shopping and occasional school pick-ups. The crucial considerations are convenience and practicality, ease of use and reliability. A five-door medium SUV such as a 2007-2015 or brand new Toyota RAV4/Vanguard, Nissan X-Trail or Kia Sportage in no particular order and depending on your budget, will be suitable.

The three SUV options are neither too big nor too small. They are easy to manoeuvre around city traffic and park at shopping centres or tight school parking lots.

These SUVs also have ample passenger and load space to carry three or four playful grandchildren as well as a week’s shopping in the cargo bay at the back.

In case your mother is not carrying any children, she can ramp up cargo space by folding down the second row seats to carry both supermarket and market shopping. The above SUVs are comfortable and easy to drive over suburban uneven roads and in busy city traffic.

Reliability of the two SUVs is augmented by easy availability of spare parts, good build and performance quality as well as strong dealerships to support parts supply.

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Hello Paul, I am keen on replacing my old Toyota Premio with a Toyota Progress. My friends are, however, discouraging me saying it is a very unreliable car. Kindly share your opinion.


Hello Justus, the Toyota Progres is not an unreliable car as such.  The reliability of a Toyota Premio and Toyota Progres may differ due to factors such as service or repair history as well as different driver experiences.  When buying a used Progres or any other model, it is important to look at factors such as the car’s age or mileage as this will indicate what age-related maintenance or repair procedures are due.

Consider the service or repair records where available as this tells you what repair or service actions you need to carry out should you own the car. If the used car is available, carry out a technical inspection with the help of a trusted mechanic. This can help you avoid hidden technical faults or poor accident repair, which will make the car unreliable to run.

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