If you feel that your car is not running the way it should and the engine is not running smoothly, you are probably wondering what the cause might be. The answer is not always obvious, because a great many different factors affect the proper operation of the powertrain. Today I would like to present some of the most common reasons for rough engine running in individual systems. Enjoy the read.
How can you tell that an engine is running rough?
When exactly do we know that our powertrain is not running properly? Jerking while driving, problems with starting and pulling away, and a general loss of power signal that the engine is not working correctly. An experienced driver will immediately sense that something is wrong with their car and that not everything is running as smoothly as it should. You need to react immediately, because even the smallest changes may indicate problems that can lead to faults and costly breakdowns.
What can cause rough engine running?
Rough engine running is certainly a cause for concern, but it is hard to say definitively what causes it. It may be a sign of various faults in the car - from trivial reasons to more serious damage. The causes can vary depending on whether it is a petrol engine, a diesel, or a car with an LPG system.
Below I will describe what is worth paying attention to and present the potential causes of rough engine running.
Rough engine running on petrol
Modern petrol powertrains are highly complex, and the large number of components means that after just a few years of use, one of them may start to malfunction.
Rough engine running at low revs
Rough engine running at idle is most often the result of a malfunction in the fuel supply or ignition system. In petrol engines, the cause is most often worn or damaged spark plugs, leads, or ignition coils.
If your car has a problem with the ignition coils, you will feel jerking during acceleration, and you will also notice difficulties when starting the engine. The “Check engine” light should alert us to the irregularities - in such a case, the ignition coils need to be replaced (the cost of one is from 150 to 400 zł).
Rough engine running at low revs may also result from worn spark plugs. It is worth keeping them in excellent condition and replacing them regularly, especially since the cost is not high - one unit costs from a few to several dozen zlotys. This will also help solve problems with starting the powertrain, as well as increased fuel consumption.
The cause of rough engine running at low revs can also be sought in the ignition leads. Although they have a long lifespan, over time they may wear out, because their rubber sheathing is exposed to both high and low temperatures. Also, even the slightest mechanical damage to the insulation of the ignition leads can result in their failure, which can disrupt the voltage supplied to the spark plugs from the coil. Sometimes a thorough cleaning is enough, in some cases replacement will be necessary - the cost is about 100 zł for the leads plus labour.
Electronics problems in petrol cars
In modern powertrains there are plenty of various sensors that determine proper operation:
- engine control unit,
- knock sensor,
- lambda probe sensor,
- airflow meter sensor,
- camshaft sensor’
- crankshaft sensor.
Unfortunately, a large number of such components increases the likelihood of a fault that may lead to various kinds of irregularities - from jerking while driving to starting trouble.
Unfortunately, we often also deal with a failure of the main control unit, which can be very problematic. It may become damaged, or it may have been improperly installed by the manufacturer. This component is very sensitive to moisture and high temperatures and can wear out. The cost of repairing its failure can be as much as several thousand zlotys.
Rough engine running after starting on petrol - clogged fuel and air filter
Proper airflow in the combustion chamber is very important for the functioning of the engine. This is mainly handled by the rubber components leading air to the powertrain and by the air filter.
You should also very carefully monitor the level of contamination of the fuel filter - its good condition affects the proper flow of exhaust gases through the exhaust system. If the fault is not on the filter’s side, you should carefully check whether the other components such as pipe bends, welds, or the catalytic converter are functioning properly.
If you notice a problem during hard acceleration, the cause is probably a damaged fuel pump that is not providing adequate performance. - replacing it with a new one costs from 400 to even 2000 zł.
Rough engine running in a diesel
Diesel engines also have their problems and relatively common minor faults related to individual components.
Diesel powertrains have a sensitive injection system that can lose its seal for various reasons. The pressure loss is often caused by leaking washers under the injectors - you will then observe a loss of compression, which will cause it to lose power, thereby making it impossible to achieve proper performance.
The injectors themselves may also be damaged, which would be suggested by problems starting the car, jerking, significantly higher fuel consumption, or black smoke.
Rough engine running at low revs on a diesel
A damaged fuel pressure regulator can also cause rough engine running. A properly working fuel pressure regulator is responsible for maintaining the right pressure on the rail and the proper metering of diesel fuel - otherwise the engine will surge at low revs.
Its durability decreases after about 150-200 thousand kilometres. This component cannot be reconditioned and you will have to replace it, which costs about 600 zł.
Rough engine running on LPG
Rough engine running on gas is a very common problem when driving on LPG. In most cases this is influenced by a poorly matched system or cutting costs on servicing. Rough engine running on gas will most often concern the ignition leads. It is their improper functioning that is in most cases the cause of problems, because they are one of the more important links in engines powered by two types of fuel.
Rough engine running after starting
An LPG system requires higher voltage in the ignition system, which translates into faster wear. Due to the higher operating temperature, it is recommended to replace the ignition leads after driving 30-40 thousand kilometres.
To avoid trouble, always choose better-quality cables that will provide proper insulation from external factors and protection against the high temperatures generated during gas combustion. They should also be properly matched to the other subassemblies and professionally fitted. Their improper operation can lead to damage to the catalytic converter or the intake manifold, and this will entail costly repairs.
Rough engine running - lack of power
A loss of power and jerking can also result from poorly matched injectors and replacing filters too rarely. These components should be replaced every 10-15 thousand kilometres - preferably during annual inspections.
Another problem can be the hoses delivering gas to the injectors, which wear out and crack over time. A loss of seal will cause fuel to be metered in the wrong amount, which will translate into a drop in performance and improper engine operation.
All of the above-mentioned problems can be contributed to by using poor-quality gas, which can have a negative effect on the system components made of plastics. That is why you should refuel your car only at trusted filling stations.
Rough engine running with the air conditioning on
After turning on the air conditioning, the engine is loaded by driving the compressor and must produce more power. The cause of rough engine operation in such a situation may therefore be either the air conditioning system or problems with the powertrain.
Responsible may be the contamination of components such as the stepper motor, the EGR valve, or the throttle body, as well as too low or too high an amount of refrigerant, wear of the V-belt, the compressor, and the pressure switch. In the event of any irregularities, the engine computer will incorrectly calculate the power demand, which will cause an increase and decrease in rotational speed, i.e. rough running.
Rough engine running after starting - take care of your car
If you care about the proper operation of the powertrain, take care to keep it in the best possible condition. You can do this by keeping all systems clean. I recommend using engine flush products, which, when used regularly, will be able to prevent most of the complications mentioned above. In this way you will improve the flow capacity of the oil channels, clean baked-on injector tips, and increase the lubricating properties of the oil.
Although we are not able to avoid all faults, it is worth trying to minimise the risk. Engine flush products are an excellent way to keep the engine in excellent condition for a long time.
