I also own Toyota Hilux invincible, this has to do with bad Diesel Particulate Filter. Toyota Hilux Invincible 2012 and above are EURO 5 whereas Pakistani Hilux 2020 is still EURO 2. what is euro 2 and euro 5, in short, they fiddle with exhaust system to make a same 1kd engine either euro 2 or euro 5 in attempt to minimize the harmful contents of exhaust to be released into the air, rest the engine remains same. Issue is, once problems such as these comes forward, non of the mechanic here understand anything. you are left with no option except to sell it off.
Plus few things i would recommend apart from having your dpf checked. remove your injectors(take a note of injector serial number and where it was installed to have it reinstalled in same order) and have the copper washers replaced as manufacturers recommend it to be changed after every 50k miles. that result in blowoff and symptoms are same. further, blowby also starve the engine and critical areas from engine oil reaching it.
Read the article below for better explanation.
.
Fuel-injectors-info.pdf (1.5 MB)
