Experienced gardeners share their insights in answering this question :
This engine is running too lean, it either has dirt in the carb jets, or if there is a mixture screw undo it slightly.

How to Identify and Fix Common Gardening Problems ?

We provide a variety of viewpoints on how to identify and fix common gardening problems. Our sources include academic articles, blog posts, and personal essays from experienced gardeners :

If your lawnmower`s engine is surging it could be a problem with the carburetor. The carburetor mixes air and fuel to the perfect ratio for combustion. There are passages and nozzles (called jets) that route the fuel through the carburetor. The jets meter the precise amount of fuel that is needed for combustion.
The mower surges when the carburetor sucks air through an unsealed gap in the air intake manifold instead of through the air filter. Dirty carburetor. Clogged fuel jets inside the carburetor commonly cause the lawn mower engine to surge. Clogged jets can`t provide the right mix of air and fuel to the engine.
Among the potential underlying causes are vacuum leaks, EGR system malfunctions, malfunctioning oxygen sensors, dirty fuel injectors, fuel pump malfunction, faulty spark plugs, a faulty mass airflow sensor, or a faulty throttle position sensor.
Surging and Lagging

Another good indication that your spark plugs are dirty or worn is if your vehicle experiences surges of speed, resulting in a jerking acceleration. These surges occur because your spark plugs are not igniting the fuel in your engine at the proper rate, resulting in an uneven speed.

The main reasons for an Engine Surge at Low RPM are Air, Fuel, Spark, and Compression which can be detected by the below indicators: Dirty or faulty mass airflow sensor. Clogged or dirty fuel injectors. Faulty spark plugs or ignition coils.
The problem may involve an annoying change (up/down) of engine speed while cruising at a steady pace, a low drop (or even cut-out) at idle or when approaching a stop, a wild high engine speed of several thousand rpm followed by a drop to near zero, etc.
To control engine speed, a mechanical governor uses gears and flyweights inside the crankcase to detect changes in the load and adjusts the throttle accordingly.
Loose, Dirty or Disconnected Spark Plug in Your Lawn Mower: Check it out, clean off debris, re-connect and tighten. Dirty Air Filter: Clean or replace. Fuel Not Reaching the Engine: Tap the side of the carburetor to help the flow of gas. If this doesn`t work, you might need a new fuel filter.
If an engine is not getting enough fuel (this is called “running lean”), due to fuel pressure (regulated by the fuel pump and regulator), restricted fuel injectors, a vacuum leak or really anything that throws off the fuel mixture going in to the engine, this can cause the surge.
Engine Surging

In most cases, a faulty fuel pump will not draw enough fuel out of the tank. In some cases, it will draw too much fuel out of the tank and your engine will surge sporadically as you drive your automobile. You will continue to have this problem until you replace the fuel pump.

If your RPM starts fluctuating, there might be issues with the engine`s combustion process, a communication gap between the IAC and the ECU, or it can be a worn-out spark plug.
Replace the sensor with a compatible one and correctly install the crankshaft position sensor to ensure that the engine runs optimally and safely. A qualified technician can prevent further issues with RPM fluctuations while driving by installing the sensor correctly.
Spark plugs that are dirty or worn out should be replaced soon because they also cause a delayed throttle response. Oil residue can cause a weak or inconsistent spark. The weak spark that is released is not enough to accelerate.
A good spark will be blue-white and will be plainly visible in daylight. If a good spark is present, the problem is probably not in the ignition system. Check the fuel system and/or stark timing. Weak sparks are orange or red and may be hard to see in daylight.
Here are some possible reasons your RPM is going up and down while driving: Worn-out spark plugs. Vacuum leaks. Bad idle air control valve.
Engine Surging Can Be an Early Warning Sign of Ignition Problems. Engine surging is usually a warning sign that your car or truck is having combustion problems. Since a vehicle`s ignition wires and spark plugs play a major role in proper engine performance, it is likely time to check your engine`s electrical components …
There are several reasons that surging occurs. A restriction to flow or fouling in the air/gas system is one possible factor. This could be caused by a dirty charge air cooler, or dirt or contamination on a nozzle ring, for example.
Surges or transients can damage, degrade or destroy the sensitive electronic equipment in offices or businesses resulting in: Equipment damage. Equipment downtime. Losses in resulting revenues.
One of the main reasons why your vehicle could be vibrating at idle could be due to worn out spark plugs. When a vehicle`s spark plug is faulty, it can interfere with the air-fuel ratio leading to improperly firing cylinders, resulting in a misfire while idling. Replacing your spark plugs will solve this problem.
Motor mounts: It`s the job of the motor and transmission mounts to dampen vibration. When they break, you`ll feel excessive vibration, especially at idle. You can diagnose this yourself by putting your car in neutral. If the shaking lessens, you very well could have broken mounts.
The throttle position sensor (also known as the TPS sensor or Throttle Valve Position sensor) is a part of the electronic throttle control system and is connected to the throttle body and monitors your vehicle`s throttle angle.
Lawn equipment (including lawn mowers, lawn tractors, and even trimmers and blowers) is designed to run at full throttle to give the best performance. Your blade will turn faster at higher throttling, which is essential to proper cutting.
The problem may involve an annoying change (up/down) of engine speed while cruising at a steady pace, a low drop (or even cut-out) at idle or when approaching a stop, a wild high engine speed of several thousand rpm followed by a drop to near zero, etc.
If your lawn mower starts, runs briefly, then dies these are the four most common reasons that`s happening: Dirty carburetor / clogged carburetor bowl. Old gasoline that has gone bad. Dirty or defective spark plugs.

Discover Relevant Questions and Answers for Your Specific Issue

the most relevant questions and answers related to your specific issue

Belt for self popelled mower keeps breaking? Cannot keep a new belt on pulley
ANSWER : Check that the pulley isn’t seizing up and causing the belt to snap, also be sure you loosen up the self propelled mechanismn by spraying down with WD 40, too much belt tension can cause this, but it rather seems like the belt pulley seizes and the engines drive pulley keeps turning causing the belt to overheat and break or stretch and come flying off.

Read Full Q/A … : Garden

My Toro LX425 keeps on blowing 20 amp fuses when I am mowing the yard. Why is it doing that?
ANSWER : A fuse will blow if: a positive wire is being grounded to the frame or two much current is being passed thru it.

Read Full Q/A … : Garden

How much does a trimmer throttle cable cost? – Stihl Trimmer Throttle Cable Km 40 50 56 70
ANSWER : 27 punuds including VAT – L&S Engineering

Read Full Q/A … : Garden

LT1045 keeps breaking NEW belts after just a short period of mowing.
ANSWER : Have you checked the bearings?

Read Full Q/A … : Garden

Throttle cable On a number 40 Husqvarna Chain Saw I need to replace the throttle cable. How do I access the throttle cable on the engine end?
ANSWER : This advice is not model specific, but normally you would remove the air filter and access it that way.Usually the actual fitting of the cable to the carburettor is pretty fiddly; sometimes it is easier to remove the carb, to do it.

Read Full Q/A … : Garden

ANSWER : In my experience, and i have a good bit, when you turn the key and it always blows the fuse, the magnets under the flywheel are in direct contact with the stator (alternator). Both will need to be replaced…sorry

Read Full Q/A … : Garden

Can’t keep pole saw running. It starts fine but when i go to do something it shuts down
ANSWER : It sounds to me like you have a blockage in the high jet. There are 2 jets in the carb a HI and a LOW. If you can determine which is the high jet turn it in gently while counting how many full turns and any partial turn and write it down. (example 2 and one half turns) Then remove the high jet needle valve. Spray some carb cleaner into the hole you took the needle valve out of using the little tube that comes with the can of carb cleaner. then put the needle valve back in and turn it gently till it stops again. Now turn it back out the same amount that you wrote down. It would not hurt to do the other jet as well…

Read Full Q/A … : Garden

Husqvana keeps blowing fuse & when i disconnect a wire from the fuel managment system it doesnt blow
ANSWER : Look at the solenoid on the carb the wire starts to break and short out on the solenoid housing

Read Full Q/A … : Garden