Nitro RC car smoking | troubleshooting guide


Nitro RC cars often smoke because they run on nitro fuel. 

If you own a Nitro RC vehicle, you will always find smoke making its way out of the exhaust pipe. Well, this is a natural process. A nitro car smoking only becomes a problem when you have a smoking engine. 

The most common reasons your Nitro engine would smoke could be burning oil, overheating, or a melting wiring harness.

In this article, we learn more about the common causes of nitro RC car smoking and avoid these problems. 

Why is my nitro RC smoking?

When your nitro RC car smokes, it could be because of various factors. Some of them include:

  1. Machining oil on new engines

Usually, when you get a brand-new nitro engine, they smoke on the first run as there might be a leftover from CNC machine oil used to build the engine. After the first run, this oil residue would clear up and leave your engine smokeless.  

  1. Oil leaks from valve covers

A leaking valve cover may also cause smoke from your nitro RC car. When the valve leaks, it leaves some oil trails directly on the exhaust, making you notice some blueish black smoke. Also, spilled oils and dirt on the engine will cause smoking. You want to make sure to keep the engine clean and free of dirt at all times. 

  1. Overheating

Your RC car will smoke when the temperature levels rise more than usual. Overheating typically occurs due to the use of oversized tires, a bad thermostat, and running slow for extended periods. Running the engine too low and too rich can cause overheating and possibly damage the glow plug. 

  1. Exhaust leak

If the exhaust starts to leak from the manifold, there’ll be smoke coming from under the hood.  

  1. Melting electrical wiring

This happens more often than others. Upgraded nitro engines come with extensive wiring harnesses that melt when they constantly rub against the exhaust. The melted plastic falls on the engine when the harness melts and produces smoke. You want to keep in mind that melted plastic on the engine can cause the engine to fire. 

How can you tell why your nitro engine is smoking?

It’s very easy to diagnose the cause of a smoking engine with the color of the smoke. 

Basically, the smoke may appear whitish, bluish-black, or black. 

  • White smoke: this situation shows the cause of the smoking is the engine cooling head. The cooling head might be loose, tighten it.  
  • Blue smoke:  Your RC car is running too rich. Turn at 1/8 HSN to lean out in bits and stop the smoke. It could also mean an oil leak at the bottom of the cylinder head. 
  • Black smoke: black smoke indicates that the sheath on the glow plug wire may be burned. It may mean a leaking glow plug. Make sure the copper ring on its head is there and it’s tight. 

Smoke coming off the cooling head

Smoke coming from the cooling head usually looks white and smells sweet. 

If you notice this smoke, your engine is running way too lean. A lean engine causes overheating and makes the cooling head turn white.

Smoke coming from the glow plug

Smoke from the glow plug may also result from a lean, too rich, overheated engine. 

When the engine is too lean, smoke will come from other places besides the exhaust. The oil in the fuel will build up and burn and damage the glow plug when it is too rich. 

To identify the problem, try to check the temp, and see if it is low or high. 

What amount of smoke is not normal

How much smoke is too much will depend on the kind of fuel, air Restriction, Exhaust system, Glow plug, Ambient air temp, barometric pressure, Humidity, and altitude of your RC car. Likewise, an overly lean engine may cause more smoke on your nitro car. 

Generally speaking, the normal amount of smoke of nitro RC cars is foggy-white, which you can see through and fades almost immediately.

Does a rich fuel mixture produce blue smoke?

A rich fuel mixture will produce blue smoke on the exhaust. 

When you see a cloud of blue smoke, it means you’re burning oil, and when you richen the nitro engine’s mixture, you’re adding more fuel and oil than air to the nitro engine. 

Does the type of fuel affect the amount\colour of the smoke?

If you’re new to RC hobby, you will often wonder if the type of nitro fuel you use affects the nitro fuel percentage or the color of the smoke. 

Understand that there are different fuels for types, methanol, nitromethane, and oil. Using a different percentage than manufacturers stated can damage the nitro engine, especially if the engine is not tuned right for it. 

Likewise, the type of fuel you use can change the color of the smoke. 

Does RPM affect the amount of smoke?

Technically when you run your car at high speed, the exhaust produces smoke but not so much that you will tag too much. On the other hand, running your RC car at too slow a speed can cause the engine to overheat, which causes the engine to smoke. 

Can you drive with your engine smoking?

When you notice large amounts of thick smoke coming from your engine, no matter its color, you need to be careful, as it may mean costly repairs and replacement for you. When you notice smoke, you should drive your RC car as slow as possible. 

Although running too slow can cause the engine to overheat and smoke more, it’s best to be on the safe side. 

Why does nitro engines produce smoke

Generally, nitro engines produce smoke when they run too slow, lean, rich, and have a faulty glow plug, overheat, and oil leaks, which fall directly on the engine. 


While it’s not an exact science, it’s easy to spot the cause of smoking that comes from the exhaust. Watch out for the color of the smoke and how they smell to know where the issue is. If you notice too much smoke shooting out from the engine, troubleshoot the problem and make sure to carry out quick maintenance.