I drive a Toyota Mark X 2013 Model. The car’s acceleration has been great even when driving uphill. But lately, it loses power when doing uphill and it remains at the same speed however much you press the acceleration pedal; something it was not doing before. What could be the problem? Hussein
Hello Hussein, reduced engine acceleration and performance when driving your Mark X uphill can be caused by one of two faults with its petrol engine; a bad mass air flow sensor or faulty fuel pump. Faulty engine management sensors such as the mass air flow sensor (MAF) can cause a loss of power when driving uphill.
The MAF monitors changing air volume and temperature as you drive uphill, downhill or along a flat stretch. This information helps the engine management system regulate the air-fuel ratio according to the different power needs of the engine in the different driving situations mentioned above. A sort of altitude compensation.
When the MAF fails due to age or dirt damage, the engine management system reverts to pre-programmed values or limp mode just to get you along until you get the problem rectified at a garage. A computer diagnosis can confirm that fault. The other possible cause of engine power loss while driving uphill is a faulty fuel pump. If the fuel pump pressure is low, it can cause reduced performance when driving uphill. That can be confirmed by assessing the engine fuel pressure values.
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