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Q: Vehicle failing to pull, smoking black

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I am driving a Isuzu Big Horn 4JG2, 1994 model. When driving on plains (.i.e flat surfaces), the vehicle accelerates up to a maximum of 90Km/hr. However, when driving up steep slopes, the vehicle slows down to around 10 to 20Km/hr. It produces black smoke when driving up steep slopes. My Mechanic has tried replacing the turbo and serviced the injectors, replaced fuel and air filters but there is no improvement. What could be the problem? Daulos Mauambeta, Malawi

My car has 215000 miles.
My car has a manual transmission.

Hello. If the vehicle is struggling when traveling up inclines then it may be possible that there is issue related to the engine, or possibly transmission. Black smoke is produced when the engine is unable to properly burn all of the fuel that is being delivered into the engine. This can be caused by excessive fuel or lack of air. If the you have already serviced the aforementioned components then the next things I would look at are the vehicle’s fuel system. A malfunctioning fuel pump or fuel pressure regulator may be sending excessive fuel to engine, causing your issues. The same can also occur if there is an issue with one or more of the engine’s sensors that causes the computer to deliver excess fuel incorrectly. I would also make sure to use lower gears when driving up any steep hills or through heavy loads, as using higher gears may put an excessive load on the engine, potentially causing your issues. As these sorts of diesel engine issues can sometimes be difficult to diagnose, I would recommend having a professional technician, such as one from YourMechanic, visit your location to diagnose what the cause of your black smoke may be.

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