Why is My Snowblower Engine Surging? The Hidden Cause 99% of Owners Miss

That rhythmic, frustrating pulse of your snowblower engine—revving up and down, up and down—is a sound no one wants to hear during a winter storm. This phenomenon, known as surging or hunting, is more than just an annoyance. It’s a clear signal that your machine is struggling for survival, starved for either fuel or air, and on the brink of failing when you need it most.

Ignoring this engine hiccup can lead to significant performance loss, increased fuel consumption, and eventual engine damage. Before you resign yourself to a costly repair shop visit, understand this: you can likely fix this problem yourself. This guide will expose the hidden causes of engine surging and provide the definitive steps to restore your snowblower’s smooth, reliable power.

What is Engine Surging and Why Is It Happening?

Engine surging is an unstable engine speed that cycles up and down without you touching the throttle. The engine tries to find a stable RPM but consistently overshoots and undershoots its target. This rhythmic variance is almost always a symptom of a lean fuel-to-air mixture, meaning the engine isn’t getting enough gasoline for the amount of air it’s taking in.

The engine’s governor, a mechanical system designed to maintain a constant speed under load, detects the drop in RPMs from the lean mixture and opens the throttle to compensate. This influx of fuel causes the engine to rev up. Now, sensing the engine is running too fast, the governor closes the throttle, the RPMs drop, and the entire cycle repeats, creating the tell-tale surging sound.

The Number One Culprit: A Clogged Carburetor

Let’s be direct: a dirty, clogged carburetor is responsible for over 90% of surging issues in small engines. Modern gasoline, particularly fuel containing ethanol, is the primary villain. Ethanol is hygroscopic, meaning it attracts and absorbs water from the air. This water can lead to corrosion inside the delicate metal passages of your carburetor.

Over time, especially if fuel is left in the tank during the off-season, it degrades and forms a gummy varnish. This sticky residue, combined with debris and water, clogs the main jet and pilot jet—tiny orifices that deliver a precise amount of fuel to the engine. When these jets are even partially blocked, the engine is starved of fuel, leading directly to the lean condition that causes surging.

Your Step-by-Step Guide to Fixing a Surging Snowblower Engine

Troubleshooting a surging engine requires a systematic approach. Start with the simplest and most common fixes before moving to more complex procedures. Following these steps will resolve the issue in the vast majority of cases.

Step 1: Address the Fuel First

Bad fuel is a gateway to engine problems. Before you touch a single tool, you must rule out the fuel itself. Stale gasoline loses its combustible properties and can create performance issues on its own.

First, drain all the old fuel from the tank and the carburetor bowl. Dispose of it properly according to local regulations. Then, refill the tank with fresh, high-quality gasoline. Always use a fuel stabilizer, especially if you buy more gas than you’ll use in 30 days. This prevents the fuel from degrading and forming varnish.

Step 2: Inspect the Fuel Cap and Gas Tank

A lesser-known cause of fuel starvation is a clogged fuel cap vent. The fuel cap has a tiny hole that allows air to enter the tank as fuel is consumed, preventing a vacuum from forming. If this vent is blocked by ice, dirt, or debris, a vacuum can develop and restrict fuel flow to the carburetor.

Unscrew the gas cap and check the vent. If it appears blocked, clean it carefully with a small wire or compressed air. While you have the cap off, use a flashlight to look inside the gas tank for any floating debris that could be drawn into the fuel line, and remove it if necessary.

Step 3: The Ultimate Fix—Cleaning the Carburetor

If fresh fuel didn’t solve the problem, it’s time to service the carburetor. This is the most critical step and the one that will permanently fix the surging. You will need basic hand tools, a can of carburetor cleaner, and a clean workspace.

First, shut off the fuel supply using the fuel shut-off valve. Carefully remove the carburetor from the engine. It’s typically held on by two bolts and connected to the governor linkage and fuel line. Take pictures with your phone as you disassemble to remember how everything goes back together.

Once removed, the key is to be meticulous. Disassemble the carburetor, starting with the float bowl on the bottom. This is where you will find the main jet. Carefully unscrew the jet and hold it up to a light source. You should be able to see a perfectly round, pin-sized hole through the center. If you can’t, it’s clogged.

Do not use a metal wire or drill bit to clean the jet, as this can easily damage the soft brass and alter the fuel flow permanently. Instead, use the straw attachment on your can of carburetor cleaner to spray directly through the jet. You can also use compressed air or the nylon bristle from a wire brush to gently poke out any stubborn deposits. Repeat this process for the smaller pilot jet, if your carburetor has one that is removable.

Thoroughly spray down the entire carburetor body, focusing on all the tiny passages and orifices. Once clean, reassemble everything in the reverse order of disassembly. This single procedure is the definitive solution for most surging problems, whether you have a Craftsman snowblower surging or are dealing with other brands.

Step 4: Examine the Governor System

The governor is the engine’s cruise control. It’s a system of springs and linkages connected from the carburetor to the engine block. Its job is to open the throttle to give the engine more power when it encounters a heavy load, like a deep snowdrift, and then close it to maintain a steady RPM.

If the springs are stretched or the linkages are bent or binding, the governor cannot make the precise adjustments needed for smooth operation. With the engine off, gently operate the throttle linkage by hand. It should move freely and snap back into place without any hesitation or binding. Check that all springs are correctly attached and not damaged. While this is a less common issue, it’s a critical check for a persistently surging engine.

Preventative Maintenance: The Key to a Surge-Free Winter

The best way to fix a surging engine is to prevent it from ever happening. Proper maintenance and fuel management are not optional—they are essential for the health and longevity of your snowblower’s engine.

The Golden Rule of Fuel

The single most important thing you can do is manage your fuel correctly. Never leave untreated gasoline in your snowblower for more than 30 days. If you know the machine will sit unused, add a quality fuel stabilizer to the tank immediately after filling it. This prevents the chemical breakdown of the fuel that leads to varnish and corrosion.

At the end of the winter season, either run the snowblower completely out of fuel until it shuts off on its own or drain the tank and carburetor bowl completely. An empty carburetor cannot clog. This simple step will save you countless headaches the following winter.

Symptom	Common Cause	Difficulty of Fix	Primary Solution
Engine speed cycles up and down rhythmically.	Clogged Carburetor Main Jet	Medium	Remove, disassemble, and thoroughly clean the carburetor and jets.
Engine surges then stalls, especially under load.	Water in Fuel / Stale Fuel	Easy	Drain all old fuel and replace with fresh, stabilized gasoline.
Surging is erratic and inconsistent.	Clogged Fuel Cap Vent	Easy	Inspect and clean the vent hole on the gas cap.
Engine runs rough and surges at high RPM.	Fouled Spark Plug	Easy	Remove, inspect, clean, or replace the spark plug.
Engine hunts aggressively after hitting a snowdrift.	Governor Linkage Issue	Medium	Inspect linkages for damage and ensure they move freely without binding.

Advanced Causes of Engine Surging

While fuel-related issues are the dominant cause, there are a few other possibilities to consider if you’ve already cleaned the carburetor and are still experiencing problems. These are less common but can produce the same frustrating symptoms.

Carburetor Icing

In very specific atmospheric conditions—typically high humidity and temperatures right around the freezing mark (32°F or 0°C)—ice can form inside the carburetor’s throat. This ice chokes off airflow, causing the engine to run rich and then surge as the ice melts and reforms. Many modern snowblowers have carburetor heaters or shrouds that direct engine heat to the carb to prevent this, but older models, like a vintage Homco snowblower, may be more susceptible.

Spark Plug and Ignition Issues

A worn or fouled spark plug can also cause surging. If the spark is weak, it may not be able to consistently ignite the fuel-air mixture, leading to intermittent misfires that the governor tries to correct, resulting in a surge. Removing the spark plug for inspection is simple. Look for a light brown or gray color on the electrode. If it’s black, oily, or white, it’s a sign of other engine problems, but replacing the plug is an easy and inexpensive troubleshooting step.

The Subtle Threat of Gasket Leaks

A vacuum leak from a failed gasket between the carburetor and the engine block can also cause surging. This leak introduces extra, unmetered air into the engine, creating a lean condition. To check for this, you can (carefully) spray a small amount of carburetor cleaner around the gasket area while the engine is running. If the engine speed changes, you’ve found a leak, and the gasket needs to be replaced.

By understanding the root causes of engine surging, you can tackle the problem with confidence. For most owners, a thorough carburetor cleaning and a commitment to fresh, stabilized fuel will ensure your snowblower runs with the smooth, steady power you need to conquer winter. While some brands are known for their reliability, even a premium machine like an Ariens snowblower can experience surging if its fuel system is neglected.