Bad battery, Faulty engine, poorly maintained vehicles, the list goes on and on.
Distractions and speed.
while driving yur car reduces speed then pulls off with speed and backfires what can cause that
If you've got a lot of miles on that car, the most likely culprit is a clogged catalytic converter.
The engine or the Cylinder.
The profile of the car determines the aerodynamics. The more aerodynamic the car is the less power it takes to move it through the air. That power not used to move the air translates to more speed.
combustion
Horse power and gear ratio.
A car accelerates when the engine produces more power than what is needed to overcome friction. The car reaches its maximum speed (on the level) when all the engine power is being used to overcome friction.
It is possible it is one of the speed sensors.
coz your car is a wenner
The driveshaft in a car brings the power from the engine and the speed through the transmission back to the differential on a car.
The maximum velocity produced by a car is the same as its maximum speed. This maximum speed is typically limited by the car's engine power, gearing, and aerodynamics. It is the fastest speed the car can achieve under optimal conditions.