1. Engine malfunction: decreased compression in one or more cylinders, additional air is sucked into the engine intake tract. Coking of the exhaust system or damage to the exhaust gas neutralizer (if the vehicle is equipped with a catalytic converter).
2. Malfunction of the fuel system: clogged injectors and fuel filter, fuel supply system hoses. Insufficient fuel pump supply. Use of low-quality fuel.
3. Malfunction of the ignition system: failure of the spark plug, breakdown of the high-voltage circuit of the system.
4. Engine management system malfunction: failure of system sensors. If any sensor fails, the electronic control unit switches to a backup program, which allows you to get to a garage or car service center, but the engine's power and economic characteristics are reduced.
5. Clutch slippage due to wear or misalignment.
6. Malfunction of the braking system: braking of one or more wheels while driving, incorrect adjustment of the parking brake.
7. Insufficient air pressure in the tires.
8. Overloading the vehicle.
A full diagnostic of the car should be carried out by highly qualified specialists using special diagnostic equipment, so contact a car service.
You can carry out the following work yourself.
1. Check and adjust the air pressure in your tires to the correct level.
2. Check the operation of the service brake system and the parking brake. It is not necessary to remove the wheels for this. Find a flat section of road and, in dry, windless weather, conduct a test run to determine the vehicle's coasting. The car must be fully fueled and only the driver must be in the car. Accelerate the car to 50 km/h, level off the speed, then turn off the gear and coast until it comes to a complete stop. Perform another run in the opposite direction. The run-out should be about 500 m.
3. Check the operation of the ignition system as described above.
4. Check the operation of the clutch. The initial check is carried out on a level area free of obstacles. Set the accelerator pedal to a high idle speed - approximately 1500 min⁻¹. Brake the car with the parking brake. Depress the clutch and engage first gear. Then begin to slowly release the clutch pedal. If the engine stalls, the clutch is working properly and is not slipping. If the engine does not stall, the clutch is worn out and needs to be replaced or the drive adjusted (see "Removing and installing the clutch").
5. Check the engine management system for proper operation.