Why does my car feel like it’s chugging?
By
Vroomouk
This blog will explain the factors that can cause the car to feel like it’s chugging. The following questions are also answered in this blog: what does chugging mean while driving the car? How to prevent the car from chugging?
Why does my car feel like it’s chugging?
Your car can feel like its chugging due to the following reasons:
- Low fuel pressure.
- Incorrect mixture formation
- Fault in fuel vapor purge system
- Fault in fuel pressure sensor
Let’s take a closer look at each of the factors:
Low fuel pressure.
Most cars today use low-pressure and high-pressure fuel systems. The fuel pressure in the system is monitored by the engine control unit. Ideally, the fuel pressure in the high-pressure system is around 250 bars for gasoline and 2000 bars for diesel engines.
If the actual high pressure in the fuel system is not equal to the specified pressure then the engine cannot maintain its engine speed. The car feels like it’s chugging or it can also stall if shifted into the drive gear. The fuel injection is controlled by the ECU and a drop in pressure means there is not enough fuel in the system to inject.
Likewise, the fuel pressure in the low-pressure system of petrol as well as the diesel engines is between 4 bars to 8 bars. If the fuel pumps in the low-pressure system fail, the high-pressure system will also not work properly and the engine will start chugging.
The car can even stall if the low fuel pressure drops completely. The pressure in the fuel system can be checked by an OBD-II scan tool, there can be fault codes in the ECU related to the low fuel pressure in the fuel system.
The pressure in the fuel system can drop due to a faulty low or high-pressure fuel pump. In diesel engines, it can also drop due to a faulty quantity control valve. The fuel high-pressure system is tested only when the low-pressure system is working correctly.
There are also fuel filters before the low and high-pressure fuel pumps. The fuel filter in the low-pressure fuel pump prevents dirt from entering the fuel lines. The diesel lines use a fuel filter integrated with a fuel heater and water content detector in order to protect the fuel system.
If either the fuel filters are clogged, the fuel pumps cannot develop the required pressure for the fuel system. This is a very common cause for the car feeling like it’s chugging at high speeds.
Incorrect mixture formation
The car feels like it’s chugging if the air-fuel mixture is either too rich or too lean. The engine control unit is constantly adjusting the air-fuel mixture in the engine with the help of the oxygen sensor. An air mass sensor or air temperature and pressure sensors are used to measure the air entering the intake manifold.
If there is a leak in the intake manifold downstream of the air mass sensor, air can enter the intake system and create a leak mixture in the combustion chamber. As the leak is downstream of the air mass sensor, the air entering the system is not measured by the engine control unit.
Similarly, if a fuel injector is stuck open, it can inject more fuel than the desired quantity of fuel into the combustion chamber. The engine control unit cannot compensate for the excess fuel and the car can jerk while driving.
The fault in the mixture formation can be identified after checking the adaptation data in the engine control unit. If the mixture is lean then unmetered air is entering the system. A rich mixture is caused by a faulty fuel injector.
Fault in fuel vapor purge system
The fuel vapor purging system is only used in gasoline engine-powered cars. The fuel vapors in the fuel tank are collected in the charcoal canister and a purge valve is used to purge the canister into the intake manifold.
The purge valve is controlled by the engine control unit as the fuel vapors are injected during the purging function, the engine control unit reduces the fuel injection quantity for the duration of actuation of the purge valve.
Due to a faulty purge valve, the car can feel like it’s chugging as the injection quantity is reduced by the engine control unit and fuel vapors are not entering the intake air. Leaks in the fuel vapor system are unlikely but they can also cause mixture formation issues that lead to fluctuations in the engine speeds.
Faulty fuel pressure sensor
The fuel pressure sensor is located on the fuel rail that is used to store the fuel under high pressure. The signal from the fuel pressure sensor is used by the engine control unit to regulate the fuel pressure in the high-pressure fuel system.
The engine control unit cannot regulate the fuel accurately if the fuel pressure sensor is faulty. It can cause the engine speed to fluctuate and the car feels like it’s chugging. If the power supply of the fuel pressure sensor is 5 V and the signal line resistance is less than 1 ohm then the fuel pressure sensor is faulty.
What does a chugging feeling mean while driving a car?
While driving a Chugging feeling means that the engine is about to stall and the car jerks. There is also an erratic throttle response. The Chugging can occur all the time or only at a certain engine speed. It is not safe to drive the car when it is chugging.
The engine can stall if it cannot overcome the requested torque as it is only operating on the fuel that is stored in the fuel rail. When the low-pressure pump completely stops sending fuel to the high-pressure system, the car will break down.
How to prevent the car from chugging?
It is possible to prevent symptoms like chugging and jerks by following the steps given below:
- Always use good quality fuel in the car. The fuel injectors in the car can be cleaned using fuel additives. There is no need to disassemble the fuel system.
- Using a gas line antifreeze can help to prevent blockage in the fuel line. The gas line can also remove the water content in the fuel tank.
- Replace the spark plugs according to the replacement schedule set by the car manufacturer.
- Keeping the fuel at the half tank is a good way to prevent low pressure in the fuel system.
- Replace the fuel filter according to the service schedule of the vehicle.
If there are aftermarket devices like a piggyback engine control unit and a performance remap, it can also cause jerks as the fuel system is not designed to operate with a modified system.
Conclusion
This blog explained the various factors that can lead to jerking or chugging while driving the car. Always check the fuel filler lead for the information on the appropriate fuels, incorrectly fuelling the car will damage the fuel system and the company will also reject the warranty claims.
