ATV Won’t Stay Running, Runs Rough, Or Idle Problems – How To Fix

Does your ATV not want to stay running? Does it die when idling or shut off when giving it gas?

I’ve found it can be anything from a bad spark plug, bad gas, to even the odd-ball of the key-switch wires coming loose. That one drove me crazy, the ATV would run fine but when the key switch was hit just right the engine would turn off. Even putting in a new key switch didn’t fix the problem. It was only when I saw the bent connectors that I realized that was the problem.

Most often, I find the reason an ATV won’t stay running is either the fuel, carburetor, or spark plugs.

The carb’s jets can get clogged, the floats stick or are damaged, or simply the gas is bad or contains water.

It could also be things that lead to and from the carb or gas, like the fuel lines, fuel selector, fuel filters, and even air filters that can cause issues.

What To Do First – Change The Spark Plugs

When I have an ATV or side by side that doesn’t run right, I always replace the spark plugs first.

Even if the spark plugs look fine, replace them.

It’s such an easy thing to do, at least on some ATVs, and a cheap thing to do that you would be crazy not to do it.

Honestly, you should be replacing your spark plugs once a year. Some manufacturers say you can go X many hours but replacing your spark plugs yearly can stop future headaches.

Check Air Filter And Intake

The second thing to check and doesn’t require much effort is the air filter and air intake.

Make sure the air filter is not too dirty.

I’ve had guys with mud caked onto their air filters and wondered why their ATVs don’t run right. The same is true with guys who have piles of sand in their airbox too. You need to keep this area clean and use proper filters for your riding conditions.

Don’t forget to check hoses around the airbox and engine. I’ve had pin-holes in vacuum lines that caused idle issues that drove me nuts until I found them. The hose didn’t even look old or worn out, but under the crevis was a small hole that was the cause of all my issues.

I’ve also had lines get crimped out of nowhere that lead to running problems, so be on the lookout for crimped lines.

Check The Fuel

If the unit has been sitting for a while, especially outside, the next thing you should check is the fuel.

Gas goes bad, and if you’re not adding fuel stabilizer when you store your ATV, this could be your issue.

It’s also not uncommon for water to get in your gas and cause running issues. Sitting outside uncovered and people bogging the engines in mud can lead to water getting in the gas.

Bad gas can also cause a fuel-injected model to act funny and often throw a check engine light.

Safely remove and dispose of the bad gas and put some fresh gas in the ATV. I like storing my ATVs near-empty If I’m not going to be riding for months, so when the riding season comes, I can pour some 93 octane in to freshen up what little bad gas is in the tank.

If the tank is too full, adding fresh gas or gas boosters won’t help. You need to remove the bad gas first.

Important: I need to say this as even the best of us make this mistake, but… make sure your ATV has gas. An ATV will run rough or shut off if it doesn’t have enough gas in the tank. You’ll be surprised how often I need to remind people to check the gas level.

Check Fuel Filter and Fuel Lines

If the gas is good, the next thing to check is the fuel filter and fuel lines.

If the quad is over 5 years old, and you never changed the fuel filter, now would be a good time to do so. A dirty fuel filter can cause an machine to not idle right.

Fuel lines decay over time and can cause an engine not to stay running.

One common way to know if your fuel lines are bad is that the ATV will run fine when on reserve. People use “ON” more than reserve, so those lines wear out slower.

The fuel selector or fuel peacock can also go bad and cause running issues.

If your ATV is fuel injected, it won’t have a fuel selector, but it will have fuel lines.

Clean Or Rebuild Carburetor

If nothing else worked and your ATV has a carburetor, you’ll need to get it cleaned or rebuilt.

If it’s a small ATV (kids), the carburetor being clogged is just a common thing with them as they’re so small. The funny part is that sometimes with the cheap ATVs, it’s often cheaper to buy a new carb than to rebuild them.

Quads above 300cc with carbs don’t clog as easily, but they can still clog.

This video below does a great job of showing you what to do to clean an ATV carb here.

Fuel Injected ATV Won’t Stay Running

A lot of what we talked about focused more on carbureted models but a lot of ATVs and side by sides are fuel-injected these days.

You’ll know you have a fuel-injected ATV because they often brag about it with stickers like “EFI” or “Fuel Injected.” Your owner’s manual will also tell you. Another sign, while not 100%, a fuel-injected engine doesn’t need to be choked to get started though some carb ATVs will have an auto-choke.

With fuel-injected ATVs, I find bad spark plugs and bad gas to be the most common problem for them not to stay running. Then the oddball ones like holes in the vacuum lines or computer problems come up far fewer.

Computer Problems – Bad Electronics Can Cause An ATV To Shut Off

Fuel-injected engines have computers that control everything about the engine and can cause issues like it not staying running.

The easiest one to fix that may be why your ATV won’t run right is the TPS (throttle position sensor) needs to be reset. This can only be done by the dealership or repair shop with the correct computer tools.

A damaged ECM (Engine Control Module) can also cause odd running problems though it’s quite rare.

I’ve even seen ATVs with idling problems due to a bug in the software and needs an update which the dealership can only do.

You have other sensors that can cause problems too, like the MAP sensor. You’ll need to hook it up to a computer to read the fault codes to know if a sensor is bad.

Check Battery Connections

I’ve had an quads come in that would start fine, but it would shut off if the owner did anything too aggressive.

Come to find out, the battery cable came loose and was rubbing on the frame, causing it to short out and then shut off.

Since many can have odd battery placements, you find people installing their batteries all wrong, and the wrong things touch and cause all kinds of problems.

A loose battery connection can also cause an ATV to not stay running. Corrosion or damaged wires can do this too.

Older ATVs can run without a battery, but newer ones need the battery to keep a float charge to power the electronics like the computer, fuel pump, and power steering. If there is no battery or a loose connection, and everything shuts off.

Killswitch Or Key Problems

Some more outliers that may cause your ATV to not stay running can be the kill switch or the keys.

If the ATV shuts off at idle and feels random, this could be your problem.

A bad killswitch could be vibrated so much at idle that it flips off. The same can happen to the key, especially on digital keys.

A lot of the digital keys use magnets to wake up the quad to read the code. The thing is that magnets wear out over time, and the engine’s vibration and a weak magnet could be just enough for it to lose contact and shut the engine off.

Sometimes it’s not the key. I once had an ATV that would sometimes not start, and if it did, it would randomly shut off. The key was fine, but the key switch wires were loose, and when it was sitting just right, the engine would shut off.

Bad Fuel Injectors

If your ATV is fuel injected, sometimes one fuel injector will go bad and cause idling problems.

I’ve had bad fuel injectors cause random starting issues as it was slowing leaking into the cylinders and flooding the engine.

If you have one fuel injector go bad you should replace them all just to be safe.

Bad Fuel Pump

A worn-out or broken fuel pump can keep an ATV from running.

It may have enough power to prime the engine to start but gives up soon after, and thus the ATV won’t stay running.

The fuel pump is most often located in the gas tank. While not hard, it can be dangerous, so I suggest letting the dealership do this one.

Engine Overheating – Shuts Off After A While

If the ATV runs fine unless it’s been running for a good bit and then shuts off, you could have an overheating issue.

Today, most models will shut the engine off if it’s been running over temperature for too long.

The radiator could be clogged, or the cooling system is not working due to a leak or damaged cooling lines.

Aftermarket Parts Causing Running Issues?

Sometimes it’s the aftermarket parts you put on that can cause an ATV not to keep running.

I’ve seen guys put tuners in, and everything seems fine, but weeks later, the tuner goes bad, and it stalls out. Of course, they don’t think it’s the tuner as it’s so new, so they chase many of the wrong things.

If you have an ATV that’s been modified a lot, check the mods to make sure they’re not causing your issues. Also, make sure they’re done correctly and not hurting your ATV in the long run.

Even simple mods like adding a new exhaust should be checked.