If your ATV or side by side won’t idle when cold, there are a few things you can try to fix it.
A lot of the time, it is a simple fix.
Other times it may require a lot of effort, but it’s not a huge deal for most.
Carbureted or Fuel Injected
Before figuring out why your ATV won’t idle when cold, you need to determine if it is a carbureted or is a fuel-injected engine.
The way to know if you have a carbureted engine is if it has a choke. If you need to pull the choke in to start it, then it’s carbureted.
If you don’t have to choke the engine to start, then it’s fuel-injected.
Carbureted Engine Won’t Idle When Cold
If you have a carbureted engine that won’t idle when it is cold, it’s most often because the carburetor needs to be clean.
Cleaning the carburetor is an involved process; if you have never done it before, you need to take it to the dealership or repair shop near you.
Here is a video if you want to see what’s involved with cleaning an ATV carb.
Before you take it to someone, I would try a few things first as it’s often fixed a cold idle problem for me.
- Change the spark plugs.
- Empty the gas tank and put fresh gas in.
- Put in fuel system cleaner. (ad)
- Clean or replace the air filter.
- Replace the fuel filter.
- Check all lines and airbox for any damage.
I’ve had great luck replacing spark plugs and adding fuel treatment cleaner to an ATV that idles rough.
Frequently, the issue is just bad gas. Carefully draining the old gas and refilling with fresh gas along with a fuel treatment can be beneficial. This is particularly relevant for ATVs that have been idle for a while, as gas degrades over time and can clog the carburetor. While a fuel treatment additive can help clear this out, if the problem is severe, the carburetor may need to be cleaned or rebuilt.
Also, damaged air and vacuum lines can cause idle problems, so check any lines for damage and cracks.
Fuel Injected ATV Won’t Idle When Cold
A fuel-injected engine not idling when its cold can be a tricky one. Often for a carbureted, a good carb cleaning, new lines, and fresh gas fixes most idle and running problems.
A fuel-injected engine is controlled by a computer and often more forgiving than carburetor engines, especially when starting. But if they start to have idle problems, it can be more mysterious.
The good news is that fixing or replacing the items below often fix most fuel-injected ATVs idle problems.
- Change the spark plugs.
- Empty the gas tank and put fresh gas in.
- Add fuel system cleaner. (ad)
- Clean or replace the air filter.
- Replace the fuel filter.
- Check all lines and airbox for any damage.
Since computers are used for fuel-injected ATVs, they often have a throttle position sensor that needs to be reset. The bad news is this can only be done by the dealership for some ATVs. This sensor being off a little can cause all kinds of running and idle issues, but it’s a simple fix.
Adjust Valves
If nothing else worked and your ATV still won’t idle when it’s cold, then you need to adjust the valves.
Valve adjustment is a maintenance item that needs to be done, and if they don’t line up correctly can cause all kinds of running issues.
It’s best to let your dealership do this for you, but if you have the tools and the time you can do it yourself.
Here is one example of adjusting the valves for a Can-Am 500.
How To Start An ATV When It’s Cold
When starting an ATV that is cold, it’s best to let it idle for 10 minutes to warm up.
Letting it idle for 10 minutes is especially important for carbureted engines. However, it’s still a good idea to let fuel-injected models idle for a few minutes when it’s cold so the oil and components can get to an operational temp.
Not letting your ATV warm-up can cause idle problems, especially with carbureted engines. A carbureted engine will be groggy and not want to stay running when it’s cold. So you may not have an idling issue, but instead, you didn’t let it warm up first.
A fuel-injected engine is better at balancing itself to keep it running but letting it warm up is still good to do. This is why it can be mysterious for a fuel-injected engine to give idling problems as the computer is saying what to do, but something is not listening or working correctly.
Tip: Don’t touch the throttle when starting a fuel-injected ATV. I know a few dirt bike guys will play with the throttle on their dirt bikes when starting but you don’t want to do this with ATVs as this puts it in a drown mode and will keep the ATV from starting.
How Cold Is Too Cold For An ATV?
The colder it is, the harder it will be to start your ATV.
An ATV can perform in -30C (-22F), but it’s best to have winter-grade oil and watch the battery.
When it gets too cold, the battery can freeze up. One solution when the quad is sitting and not running is to keep a solar battery charger (ad) on your battery, which helps keep it warm as it’s always charging when the sun is out. Or use a smart battery charger if the sun is not getting to it, but keep in mind, many battery chargers can’t work in too low of temps either.
Another option is to get a block heater.
Either way, it’s best to let the thing warm up for 10 minutes in extremely cold conditions.