Fixing A Smoking RC Car – A Simple Guide

It can be very difficult to determine how much smoke is acceptable when it comes to your RC car. Unless you have a Nitro RC, you shouldn’t be seeing any smoke at all coming from your car. If you do see any smoke coming from your electric RC, it’s almost a guarantee that you’ll need to replace some parts.

If you do run a Nitro car, naturally, there should be some smoke making its way out of the exhaust pipe but not from the engine or other parts of the car. How much smoke the exhaust should produce varies depending on the model of your car and the type of fuel you’re using.

This article will help you identify the parts of your electrical RC causing the smoke and advise on how to proceed. As for Nitro RCs, there’s a lot to learn about smoke coming from the exhaust or engine. The exhaust is expected to produce smoke but the engine is not. Let’s look at all the factors that could cause your electric RC to smoke or excessive smoke from a Nitro car.

Why Is My RC Car Smoking?

Smoke coming from your RC could be due to a number of factors:

  1. Your gear mesh might be too tight.
  2. Over geared motors can cause smoke.
  3. A faulty ESC/FET can cause smoke.
  4. It could be the CNC machining oil on new engines.
  5. You might be running your engine too lean.
  6. Running the engine too rich can also cause smoke.
  7. Spilled WD-40 or ARO can cause smoke.
  8. Your tires might be too big.
  9. You might be running the RC too slow.

Your Gear Mesh Might Be Too Tight (Electric RC)

The gear mesh is the spot where the pinion and spur gears meet and link up with each other. If the two gears are meshed together very tightly, they won’t budge when you try to move the spur gear gently back and forth. Too tight and the gears will overheat. A gear mesh that’s too loose will strip your gears.

Related post: Overheating RC Motor? Heres What to do

You should check your gear mesh regularly as it will change over time.

  1. Unscrew your motor slightly. (Not all the way)
  2. With the motor slightly loosened you can move the motor pinion gear closer or further from the spur gear (big gear) to tighten or loosen the connection between the two gears.
  3. Move the motor towards the spur gear until it’s so close that you can’t wiggle the spur gear back and forth at all.
  4. Now move the motor slightly back so that the spur gear has just a little bit of play when wiggling it.
  5. Tighten up the motor screws.
  6. Now that the motor is screwed in all the way again you can slowly turn the spur gear around to check if the gear mesh is consistent throughout different teeth of the gear.

A good way of determining the gap between the two gears is by placing a strip of paper between the two gears and then pushing the motor pinion gear against the spur gear. Then tighten the motor screws and pull the paper out of the gears. The gap between the two gears will be the thickness of the paper you inserted which is usually perfect.

Over Geared Motors Can Cause Smoke (Electric RC)

You need to make sure that your RC is geared according to the engine. If you’ve just upgraded your motor or gears, it might be smoking because of an incompatibility issue. RC cars are designed to work with very specific gear sizes. If they’re two big your motor will have to work too hard to turn them.

A Faulty ESC Can Cause Smoke (Electric RC)

Unfortunately, there’s not much you can do about a smoking ESC. If the ESC malfunctioned or was wired up incorrectly it could have caused the problem. You will have to replace the ESC completely if this happens.

It Could Be The CNC Machining Oil On New Engines (Nitro RC)

Brand new Nitro engines might smoke a little bit on the first run as there may be a little oil left inside the engine from the CNC machine that is used to make the engine. This oil residue should clear up after the first full tank of fuel.

You Might Be Running Your Engine Too Lean or Too Rich (Nitro RC)

Too Lean

An engine that’s running too lean has more air passing through the engine than fuel. Running the engine lean can provide a bit more power but will wear out your glow plug and decrease engine life in the long run. It will also cause high engine temperatures and therefore maybe cause some engine smoking. Read further to learn how to adjust the fuel supply.

Too Rich

Just like running your Nitro RC engine too lean can make it smoke, so can running it too rich.

Too rich means that there’s too much air in the fuel to air ratio. In some cases, this can cause the glow plug to malfunction and cause engine smoke. Check your exhaust to see if there’s a lot of smoke coming from it and also check for excess fuel dripping out of the exhaust. Even though some dripping fuel from the exhaust can be common in many Nitro RC cars, this is a way of checking for fuel that’s too rich.

How to lean out or richen the fuel flow:

To adjust the air/fuel ratio, you will need to tune the high-end and low-end needles on the carburetor. Turning the needles clockwise will lean out the fuel supply and turning the needles counterclockwise will richen the fuel supply. When you “dial-in” your engine like this, make sure to adjust the needles in small increments to find the optimal setting.

The low-end needle adjusts the idling and low-speed fuel supply while the high-end needle controls how the fuel is supplied during acceleration and high speeds.

If your engine is running at very high temperatures (over 250 degrees Fahrenheit) turn the high-end needle counterclockwise to bring that temperature down. Your engine will have a longer lifespan if it’s operated between 220 and 250 degrees Fahrenheit.

Spilled WD-40 Or ARO Can Cause Smoke (Nitro RC)

Make sure your engine is 100% clean from any oil or dirt as it will start smoking once the engine gets to its optimal running temps. (Between 220 and 250 degrees Fahrenheit)

An easy way of cleaning your Nitro engine is with a small fine tip paintbrush and engine cleaner. Just like you would look after your bike engine by keeping it clean, the same goes for your Nitro RC engine.

Your Tires Might Be Too Big  (Electric RC and Nitro)

If you’ve installed bigger tires on your RC it could cause it to overheat because of the extra effort your engine needs to provide to rotate them. Besides the extra weight that big tires will add, sometimes bigger tires will catch\rub against other parts of the car causing more resistance and even some frictional heat/smoke.

Make sure your tires spin freely when you turn them with your fingers. If they aren’t spinning easily when rotating them with your fingers, this will be the cause of your overheating problem. There is some resistance somewhere which is usually frictional resistance which causes heat. If they do spin freely then you need to check your engine capabilities in terms of tire size. The tires might be too big and heavy even if they are rotating easily.

You Might Be Running The RC Too Slow (Electric RC and Nitro)

Running your RC car at low speeds for extended periods of time can overheat the ESC. This is because there’s no airflow to cool it down.


If your electric RC car is smoking, it usually means something is fried and most likely unrepairable. Electric RC cars have no reason to smoke unless there are malfunctioning parts inside that will need replacing.

When it comes to Nitro RC cars, smoke from the exhaust is normal, but only from the exhaust, not the engine or any other parts of the car. If your engine is smoking you might need to tighten the glow plug and clean your engine off if it’s dirty with oil.

Paul Good

This awesome hobby has something for everyone, whether you like to build your RC from scratch and keep modifying till you've got it to just how you want it, to track racing. You might be out with a boat, or perfecting your skills with a plane. Are you taking some cool pics with your drone? I'm sure my site will help you on your journey.

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