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Ask the Mechanic: Why is my Toyota losing power?

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Hello Paul, I have a pre-millennium Toyota Prado 3.0 turbo diesel that just goes on forever. Even after 300,000kms, it starts the first time every time, moves well and does not produce smoke or burn oil. However, in recent months I have noticed a slight reduction in power and a slight increase in fuel consumption even after regular service. Is this because of old age or is there something I can do to extend its life?


Hello Jack, you deserve a medal for keeping the old faithful Toyota on the road. Commitment to regular maintenance and use of reputable lubricants with genuine filters will keep an engine running for a long time.

The reduced power (performance) and increased fuel consumption may be a result of dirty, worn out or leaking diesel fuel injectors. Diesel fuel injectors work so hard to deliver fuel in very hot and harsh engine conditions.

Also, the after-fuel burn dirt can block the fuel injectors and affect their performance.

Dirty and blocked fuel injectors will not spray fuel optimally for quick ignition or total combustion, which reduces engine power. On the other hand, dirty or damaged fuel injectors will tend to leak fuel rather than spray it optimally into the combustion chamber. This causes fuel wastage as it goes unburnt.

The fuel system will keep delivering more fuel as you accelerate to demand performance. This causes increased fuel consumption. Fuel injectors can be cleaned with diesel fuel designed with detergent cleaners or the use of reputable fuel injector cleaners. In case the injectors are tested by the mechanic and found to be damaged they can be replaced.

Other causes of low engine power and high fuel consumption can include a faulty fuel injector pump, a worn-out turbocharger or a dirty air cleaner element. Restricted air intake due to a dirty air cleaner affects the fuel-air ratio needed for the optimum burning of fuel.


Immediately after service, my Toyota Prado diesel 2.8 started showing check engine and traction control signs on the dashboard. A computer diagnosis has not helped and the signs keep coming back when restarting the car.  Disconnecting and reconnecting the battery has also not helped. What could be the cause?


Hello Wilson, the check engine light on your Toyota will flash with the traction fault light because of an engine-related fault. It would be useful if you shared the fault code identified by the computer diagnosis for interpretation.

An attempt to erase the fault codes with the diagnostic tool or manually by disconnecting battery terminals temporarily removes the fault lights without fixing their cause. The fault light will return.

Common causes of the check engine light on the Toyota diesel engine can include a faulty fuel system due to failing fuel injectors, dirty fuel filter or low fuel pump pressure. A faulty engine management system can also cause the check engine light.

Damaged camshaft or Crankshaft position sensors, faulty engine computers or damaged wire harnesses or connectors can cause problems. An inspection by a good mechanic will help identify the cause of the check engine light and resolve the problem.

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