Lawn Mower Stalls At Idle Cause

The gasoline trimmer is not gaining momentum: the reasons and features of repair

It is not necessary to purchase an expensive and bulky lawn mower to cut grass on a small lawn; it can be easily replaced by a gasoline / electric trimmer. The device of these machines is quite simple, they are easy to use and unpretentious in maintenance. But sometimes problems do occur. One of them. when the trimmer does not develop the maximum number of revolutions. will be discussed in this article.

The reasons

Trimmers are reliable and durable (provided they are properly maintained, of course). Most often, malfunctions occur due to contamination of structural elements.

If the motor of your lawn mower does not start, does not pick up speed, does not reach the power you need, or suddenly stalls, the reason may be:

  • Poor quality fuel (fuel mixture), it may be in long-term storage or in non-compliance with the recipe for preparing the mixture;
  • Grass is wrapped around the shaft of the fishing line / knife;
  • Clogged air filter / muffler;
  • Carburettor imbalance.

Troubleshooting methods

The first three reasons are fairly easy to eliminate. If the matter is in the mixture, you need to pour out the old fuel from the tank, prepare a new emulsion from high-quality gasoline and engine oil (if your engine needs a mixture) and pour it into the fuel tank. If the trimmer is running on pure gasoline, it’s still easier.

In the second case, it is necessary to carefully free the trimmer parts from the wound grass.

The last reason a lawn mower doesn’t work properly will require a little more knowledge and skill from you.

In order to properly adjust the carburetor for lawn mowers, a specific procedure must be followed. First, clean the air filter thoroughly. The easiest way is to rinse it (it is advisable to pour water over the filter regularly after 9-10 hours of operation).

After that, in the diagram of your trimmer, which is in the operating instructions for the device, find the adjustment screws. Usually there are three of them: the first is responsible for the fuel supply, the second is for idling, and the third is designed to limit the number of maximum engine speed.

Next, turn on the unit and wait for the engine to warm up.

Tighten the first (fuel mixture) adjusting screw slowly. Catch the moment when the motor starts to stall, and turn the propeller back 45 degrees. If you didn’t have time and the motor stalled, the screw should be turned 90 degrees. Open the throttle and watch the revs increase. Next, slowly unscrew the screw (each turn is the same 45 degrees) until the moment when, at full throttle, the engine begins to firmly give out maximum revolutions.

The second screw, as mentioned above, controls the engine idle speed. By loosening it, you decrease the number of revolutions, while twisting it, you increase it. The screw needs to be adjusted so that the motor runs reliably at low revs. For better starting, speed up the engine slightly. At the same time, make sure that the motor rotates several tens of times before starting the movement of the knives / line reel. If the engine starts poorly, tighten the screw a little.

After you have adjusted the first two screws, test the operation of the unit at maximum engine speed. If necessary, you can limit it (maximum). this will protect the motor from "boiling". To do this, you need to tackle the third screw. Unscrew the locking nut until the adjusting screw can be safely turned. To increase the maximum number of revolutions, the screw must be loosened, to decrease. on the contrary, tighten. Fix the position of the screw with a nut. Test the motor again.

Remember that carburetor adjustment is not a final procedure. During the operation of lawn mowers, you will most likely have to tinker with it more than once, because an unbalanced carburetor means both increased fuel consumption and a quick failure of the candles, not to mention a decrease in the power and performance of the device.

Little tricks

  • If you are unable to tighten / loosen the adjusting screws properly, it may be that the spring is too thick and stiff. Then you can choose instead of her a more suitable.
  • If your unit does not need pure gasoline, but its mixture with engine oil, strictly observe the proportions specified in the operating instructions. There is one little thing: the recommended ratio is 1: 25 (for all brands of oil) or 1: 50 (for "native" oils). Try the first ratio first. If, with such a recipe, oil drips appear on the motor, and a strong carbon deposit forms on the candle, reduce the proportion of oil by half. This usually helps to fade traces and reduce the amount of carbon deposits.
  • To clean the spark plug electrodes from combustion products, you can use fine-grained "sandpaper". Wipe them with a dry cloth first and then gently sand them with sandpaper. If the space between the body of the device and the insulator is also clogged, a regular unbent paper clip can help clean it. To do this, briefly soak the candle in diesel fuel, and then scrape off the dirt. If the blockage is small, one procedure is sufficient. Sometimes it is necessary to repeat it several times in case of heavy dirt. After complete cleaning, the candle must be wiped dry from the remaining diesel fuel, and then it can be used as directed.
  • Please note that foreign-made lawn mowers (gasoline, electric or battery) require a little more maintenance than domestic ones. In particular, many strongly recommend entrusting the adjustment of the carburetor of a two-stroke engine to professionals, especially if your purchase has not expired the warranty period.
  • And finally, one more tip: follow all the manufacturer’s recommendations for the operation and maintenance of the device. This will prolong its smooth operation.

You will learn more about what to do if the petrol trimmer is not picking up speed.

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Immediately after the start

The stalling of the lawn mower or trimmer immediately after the start is due to the following reasons:

  • Imbalance of previously adjusted valves;
  • Initially incorrect valve train setting;
  • Clogging of the fuel supply valve by deposits;
  • The hose is worn out or loosely connected.

Due to the broken fuel injection algorithm, the lawn mower or trimmer vibrates strongly during operation.

With increasing speed

If the lawn mower (or trimmer) stalls when adding engine speed. check the device for the following symptoms:

  • Blockage or sticking of the valve built into the gas tank cap;
  • Violation of valve adjustment;
  • Failure in the operation of pistons and cylinders. from vibration during the operation of the scythe or trimmer, accidental blows directly during the mowing session;
  • Violation of the supply of the air-fuel mixture;
  • Excessive pumping of air into the motor;
  • Cracking of the fuel inlet hose, loosening of its connections.

When the air-fuel mixture is supplied in the required portions to the engine out of time, it burns the amount that has managed to come in since the last stalling, and itself stalls again.

When idling

When you run your trimmer or lawnmower at idle, you find that the device will start. but stall after, say, 5-10 minutes. The reasons may be as follows:

  • Blockage, violation of carburetor adjustment;
  • Initially incorrect setting of the carburetor valve mechanism;
  • Clogged air filter;
  • Reducing the speed of the gearbox (if any). incorrect ratio of the air-fuel mixture;
  • Throttle plugging;
  • Penetration of excess air into the fuel system;
  • Running out of fuel in the tank (and oil in the tank if the engine is four-stroke).

If there are problems directly with the carburetor, the machine will stop both after a cold start and after starting on an already running engine.

During engine warming up

If the engine heats up too quickly, overheats. the lawn mower or trimmer works unevenly, as if in jerks. Then it stalls. The reason may be as follows:

  • Boiling gasoline;
  • The ignition wire is damaged (poor insulation);
  • The coil in the ignition system has noticeably burned out, inter-turn short circuits have appeared.

The same heating is observed when using a rotary (rather than disc) damper.

Diagnostic features

A well-posed question is already half the answer. The fact will significantly speed up the search for a solution. under what circumstances does a gasoline trimmer or lawn mower stall, namely:

  • Immediately after the start;
  • When it has been idling for some time. after one or several minutes;
  • When you press the gas button (or knob). or soon after starting work at high, near-maximum speeds;
  • Under heavy load (for example, to cut bushes, mow dense and tall weeds);
  • When warmed up in the cold, it heats up unnecessarily (the lawn mower has stalled due to overheating);
  • After opening the air damper.

When the air damper is opened

The mower or trimmer stalls when the shutter is raised for the following reasons:

  • Pumping excess air due to a cracked fuel suction hose;
  • Oil seals are worn out;
  • Incorrect operation of the fuel and air metering unit when mixed.

Stop the lawn mowers in this case immediately.

The lawn mower stalls when you press the gas

Gas key lawn mowers

Hole in the fuel cap (breather) of the trimmer

Lawn mowers fuel valve

With a similar problem, you should pay attention to the fuel valve, which, when clogged, ceases to normally pass the fuel mixture. The solution to this problem is to mitigate it with a suitable tool. In addition, a problem with the circulation of the fuel mixture may lie in a dirty valve. To do this, it is enough to blow it with a stream of compressed air.

The lawn mower stalls at high engine speeds

During operation, a situation arises when, when you press the fuel mixture supply button, the unit turns not increase, but decrease. A malfunction of this nature can be caused by:

Fuel hoses for lawn mowers with filter

  • By etching atmospheric air into the combustion chamber;
  • Problems with the circulation of the fuel mixture;
  • Clogged breather in the fuel tank cap (cleaning the hole with a fine sewing needle);
  • Incorrect carburetor adjustment.

When air is leaking during the operation of the internal combustion engine, it is necessary to check the tightness of the connection of the pipes and the integrity of the gaskets in the CPG. The problem with the circulation of the fuel mixture can be solved by removing blockages in the fuel pipes leading to the carburetor. If a vacuum occurs in the tank and the fuel mixture does not flow to the carburetor, it is enough to clean the breather with a thin needle and blow it with air.

Trimmer stalls: causes and troubleshooting

The lawn mower is a mobile, high-performance tool for beautifying home gardens and surrounding areas. With prolonged use, due to wear of parts or manufacturing defects, malfunctions occur, which lead to the trimmer stalling or not starting. Since this tool is a rather complex mechanism, there may be several reasons why the lawn mower stalls.

Why does the trimmer stall

There are two main ways to troubleshoot problems: transferring the braid to a specialized center or solving the issue with your own hands. The first option is suitable for those who are ready to pay a "tidy" sum to restore the unit’s working capacity, and the second one for those who have basic locksmith skills and can independently figure out the causes of breakdowns and ways to eliminate them.

Currently, it is customary to classify breakdowns for which the lawn mower stalls into the following categories:

  • Mechanical damage to the internal combustion engine crankcase, malfunctions of the cylinder-piston group (CPG);
  • Breakdowns associated with the supply of the fuel mixture (air filter, carburetor);
  • Malfunctions due to damaged tubes, hoses, cables or ignition circuit.

Petrol trimmer stalls at idle speed

Often, when the engine speed decreases, the lawn mower engine stalls and does not idle when restarted. The main reasons for the occurrence of such a breakdown include contamination or misalignment of the carburetor, as well as clogging of the air filter.

The petrol trimmer stalls when idling

If the optimal settings of the carburetor are violated, it is necessary to clean it and re-adjust it. Clogged trimmer air filter can be dealt with by soaking it in a solution with common household detergent for several hours. If self-cleaning did not help to cope with the blockage, then it is better to purchase a new filter element in accordance with the instruction manual.

After carrying out events, the user will not face a situation for a long time when the trimmer stalls at idle and functions only when gas is supplied.

The gasoline engine does not idle

To begin with, this malfunction indicates two possible causes: failure of individual mechanisms, assemblies or sensors, as well as severe contamination of certain elements. Both in the first and in the second case, it is necessary to carry out diagnostics. The engine on injection and carburetor cars can most often stall at idle in such cases:

  • The idle speed regulator (IAC) is out of order;
  • The throttle valve is dirty or defective;
  • The carburetor channels are clogged or the XX fuel jet is dirty;
  • Reduced or broken performance of injection nozzles;
  • The mesh of the fuel electro / mechanical pump is clogged, there are malfunctions of this unit;
  • There was a decrease in the throughput of the fuel filter;
  • Air filter dirty, intake air leaks;
  • Failure of the MAF sensor, throttle position sensor, etc;
  • Clogged crankcase ventilation system;
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If the car immediately stalls or the revolutions noticeably float after the starter is turned off, then you should pay attention to the throttle assembly. The option of both clogging of the damper and wedging of the mechanism is possible. This malfunction, especially heavy pollution, occurs as a result of a long drive on fuel of poor quality, as well as untimely replacement of the air filter.

In this case, the throttle valve must be cleaned. To clean the throttle, a conventional carbikliner (carburetor cleaner) is used, and it is also necessary to blow the damper with compressed air from the compressor. If these actions did not help, then you will need to assess the condition of the oil trap. This element is an integral part of the engine crankcase ventilation system. Contamination of the oil catcher leads to the fact that blow-by gases "choke" the engine, idle speed floats and the internal combustion engine stalls.

Now let’s look at a situation where the car starts up normally, but then starts to stall (constantly or at regular intervals). A similar situation often occurs on injection cars that have an electronic engine control system (ECM).

For owners of cars that have been in operation for a long time, it is advisable to have these sensors in stock, as well as a multimeter for self-diagnosis. This is especially necessary if the car is often used for long journeys on the highway. Note that most of these sensors have an acceptable cost.

Another important point is that the car may start to stall at idle after flashing the ECU. Unprofessional correction of the factory firmware, flashing or chip tuning of the electronic engine control unit can lead to malfunctions. Although the motor after such actions demonstrates the best return under load, at high speeds, etc., in parallel, the unit is not able to operate normally at 750-800 rpm. In this case, the installed firmware should be adjusted to achieve stable operation of the internal combustion engine in all modes.

Now a few words about the carburetor. The engine often stalls on such engines precisely because of the contamination of the jets and the long absence of proper carburetor adjustment. The fact is that even small particles of debris in the fuel can disrupt the operation of the carburetor injection. Dirt can be contained both in low-grade gasoline and enter the system from the gas tank, in which deposits gradually accumulate.

Such a product is a solvent cleaner in an aerosol can. As for the mechanical fuel pump of carburetor engines, this type of pump has a filter mesh. The specified element can also become clogged, reducing the pump performance. The membrane of a mechanical fuel pump can also fail. In parallel with wear, diaphragm particles clog the channels in the carburetor.

The situation is more complicated with the injection system on the injector. If replacing the ECM sensors does not help, then you should start checking the intake manifold for excess intake air, and also exclude air in the fuel system. Then you need to move on to checking the injection nozzles, measure the pressure in the fuel rail, inspect the vacuum hoses, etc. Special attention will be required to the vacuum brake booster. We also add that regardless of the type of injection (engines with an injector or carburetor), it is necessary to check the ignition, spark plugs, high-voltage wires, the distributor coil and other elements of the system.

The motor stalls at idle

The situation when the engine stalls at idle occurs quite often. This phenomenon can manifest itself both on cars with high mileage and on new cars. It should be noted that the process of starting a cold engine with a starter can be both initially difficult and completely normal.

In other words, the engine can start well "cold" or "hot", but then starts to stall at idle. Also, in some cases, it appears that when you press the gas pedal and increase the speed, the engine starts to work stably. There are several main reasons why the engine "does not keep" idling, troit and shakes. Next, we will consider why the car stalls at idle or runs very unevenly after starting "cold", in transient modes "hot", etc.

Diesel stalls at idle

The problems of gasoline internal combustion engines described above, associated with working on the XX, are not about Bosch and diesel engines. A frequent malfunction of diesel engines is a malfunction of the high pressure fuel pump (HPP). Natural wear of plunger pairs, the presence of impurities in diesel fuel or air leakage of the injection pump leads to the fact that the diesel starts up and then stalls.

What is the result

Finally, we add that fuel lines, couplings and hoses are rubber products. For this reason, it should be remembered that natural aging of rubber occurs. On cars that are more than 10 years old, cracking of rubber hoses becomes a frequent occurrence, which leads to air leakage. It should be added that the external condition of such hoses is not an accurate indicator of their condition. The inner surface of the walls also collapses, which leads to particles invisible from the outside into the injector, carburetor or injection pump, especially in cases of a problem in areas behind the fuel filter.

The main reasons why the engine starts to stall after warming up. Frequent problems of carburetor and injection engines, fault diagnosis.

The car engine starts and stalls immediately after starting: the main causes of this malfunction. Diagnosis of possible causes, tips and tricks.

As a result, jerks and dips appear when gaining speed, the car jerks in motion in transient modes. Causes and troubleshooting.

Floating cold engine idle speed. Main malfunctions, symptoms and breakdown detection. Unstable idling of a diesel engine.

The reasons why, after pressing the gas pedal, failures occur and the engine begins to swell. Engine failures with LPG when switching from petrol to gas.

Why the engine can have increased idle speed. The main reasons for high XX revolutions on an injection engine and engines with a carburetor.

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The lawn mower stalls

When purchasing a lawn mower, you need to be prepared for the fact that, like all other similar tools, breakdowns may also occur in it that will require repair.

However, you should not immediately run to the service center and pay a lot of money to the masters who convince you of a serious malfunction in the device.

The lawn mower stalls at high revs on gas

Perhaps the most common complaint associated with petrol trimmers is "lawn mower stalls.".

Of course, the reason for this may be a rather serious malfunction. However, most often the situation is much simpler than it seems at first glance.

To cope with such a problem, first of all, try to figure out its causes on your own, because after finding out the cause, it is much easier to deal with the problem, and sometimes it even self-destructs.

In fact, the reasons are when the lawn mower stalls at high speeds, there are quite a few reasons.

Another one is the presence of faults in the power system.

In this case, the lawn mower will stall at idle speed. Misadjustment or improper adjustment of the carburetor can lead to problems with the power system.

The misalignment can be caused by vibrations that occur during the operation of the lawn mower.

Incorrect adjustment of lawn mowers can be corrected simply by adjusting it in accordance with the requirements specified in the instruction manual.

In addition, sometimes gasoline trimmers can stall due to the fact that the valve located in the gas tank cap is simply clogged or stuck.

To find out, try using a scythe by loosening the gas cap.

If the device operates properly in this mode, clean the valve.

What’s more, the lawn mower can stall due to poor fuel flow to the carburetor.

Why then does the device start, you ask?

The reason for this is that at first the fuel gradually runs into the carburetor and it is enough to work at increased power.

However, then it is produced and at high speeds the engine begins to stall.

As for the carburetor, the problem here may also be that its body is too tight.

The reason that the lawn mower stalls at high rpm on gas may also be air leaks.

This is the possible presence of a place through which air can pass during the heating of the engine.

Be sure to check the fuel inlet hose, among other things. The problem may be that it is loose or cracked altogether.

These are the main reasons why a lawn mower can stall.

When heated

The lawn mower often stops when it heats up. At the same time, it starts, works "jerky" and gradually stops. This process occurs when the gasoline in the carburetor boils or the damper is installed in a rotary rather than disc type. In the latter case, the part is changed.

It happens that the trimmer heats up if the ignition circuit wire or coil is damaged. In order for the device to start working normally, replace parts.

What could have broken

Problems with the lawn mower due to the fact that this device does not start are classified in a certain way by service specialists. They highlight faults with the following components of the mechanism:

Lawn Mower Stalls At Idle Cause
  • An engine in which the piston and bearings may wear out or fail, crack the crankcase;
  • The fuel supply system, with the possible clogging of the filter or problems with the carburetor;
  • Mechanical damage to wires, tubes, hoses;
  • Ignition circuit.

Immediately after wound up

The unit may stall immediately after starting if the carburetor is misaligned or incorrectly adjusted. this causes uneven fuel supply. The result of this is that the device vibrates distinctly. For troubleshooting, the carburetor is reconfigured, following the instructions for the mechanism.

Also, the engine stops when the fuel supply valve becomes clogged. In such cases, it is sufficient to simply clean it. If the mower started working at first, but then immediately stalled, then it is possible that the fuel enters the carburetor unit with some difficulty. Weakening the valve helps to resolve the issue, which ensures free circulation of the mixture in the system.

The stoppage can also be caused by air leaks in the presence of mechanical damage to the hose (holes, cracks) that takes the fuel. In this case, add more revolutions to the drive in order to quickly expel air bubbles from the system.

When you hit the gas

If the lawn mower stops when the throttle is pressed, the reasons may be as follows:.

  • The most common variant is carburetor adjustment failure, which occurs when the drive is under heavy load, after prolonged inactivity of the mechanism, or when it is used in difficult conditions.
  • Clogged fuel valve, which is eliminated by loosening it, as a result of which gasoline begins to flow normally through the system.
  • Loosening and drooping of the cable in the carburetor. The fuel hose may also be stretched to the point of rupture due to significant stress.
  • Clogged breather (check valve), as a result of which fuel does not flow into the tank.

If the problem is with the carburettor assembly, the lawn mower vibrates to recognize it. When the hose bursts or the cable is stretched, these components are replaced.


At idle, common reasons for trim stopping are as follows:

  • Dirty, misaligned or incorrectly adjusted carburetor adjustment;
  • Clogged air filter;

Replacing the air filter for lawn mowers

Trimmer air filter

  • Reducing the speed of the gearbox when it heats up, which is a consequence of using an unsuitable fuel mixture
  • Clogged throttle;
  • Air ingress into the system;
  • Not enough fuel to operate the lawn mowers.

At high revs

When the scythe stalls at high speeds, this is due to the following problems:

  • Clogged or sticking valve located on the gas tank cap;
  • The carburetor is out of alignment due to vibrations arising from the operation of the mechanism
  • Problems with the circulation of the fuel mixture;
  • Leakage of atmospheric air;
  • The fuel intake hose is cracked or loose.

Adjust the carburetor referring to the trimmer operating instructions. For adjustment, it is often sufficient to loosen the tightening of its housing. If there are problematic points with the circulation of the fuel mixture, then it can gradually enter the carburetor. After its development, the engine stalls at high speeds.