(Q). What could be the possible cause of a Toyota car slightly losing power and gaining when I am driving at high speed.
(A). Intermittent loss of engine power or poor engine performance when driving is often caused by a fault in the ignition or emission systems of your Toyota. There are several dependent variables or components which will cause the above situation.
It would be very useful to know the mileage and recent service history of your Toyota. There are certain ignition system maintenance procedures that ought to be carried out at 100,000kms. For instance, replacement of the long life fuel filter in the engine bay or fuel tank (depending on the year of manufacture).
This fuel filter will get clogged and restrict prompt fuel delivery to the engine as well as damage the fuel pump. A dirty fuel filter will allow deposits to pass through and build up in the fuel injectors causing their damage and intermittent poor engine performance.
You therefore need a qualified mechanic to replace the fuel filter and confirm the working condition of the fuel injectors. This can be compounded with a test to establish the fuel pump generates sufficient fuel delivery pressure. The above procedures have to be carried out by a qualified mechanic using a fuel pressure gauge or electronic tester.
The condition of the engine spark plugs and high tension leads or ignition coils (depending on the engine generation), should be verified or replaced from a genuine Toyota parts source. Your mechanic should check the engine throttle valve in case its movement is clogged by soot.
This would restrict air supply to the engine and affect acceleration power. The throttle cable should be inspected in case it is damaged. Restricted movement of the throttle cable can cause the kind of intermittent poor engine performance you are experiencing.
Finally, you need to choose your fuel source carefully. Your car is fitted with a catalytic converter which is sensitive to adulterated fuel. The catalytic converter is designed to render less harmful environmental pollutants in the exhaust smoke.
However, exposure to exhaust smoke from adulterated fuel damages or blocks it. This will restrict the outflow of exhaust smoke and affect engine performance.
