A car’s camshaft is located beneath the engine and provides the important function of opening and closing the valves of an engine. When something goes wrong with a camshaft, your car can stall more, accelerate more slowly, or even fail to run altogether. Because the camshaft function is so vital, knowing a little more about how it operates is a good idea for any driver. With this engine cam knowledge, you’ll be in a better position to spot problems with the component before they spiral out of control.
Below we run through how camshafts work, and why they’re important. We’ve also put together a list of symptoms you can expect to see should something go wrong with the camshaft sensor – the most common malfunction for this part. If you’ve ever found yourself asking the question “what is a cam in a car?”, this blog is for you!
What is a Camshaft?
Camshafts consist of two main components: the cam, and the shaft. So, what is a cam, exactly? Cams are a type of lobe, and as they spin, the intake and exhaust valves are opened. The shaft spins once for every four stroke cycle of the engine. Springs on the valves act to return them to their resting position once the cam has passed. These cams are typically egg-shaped.
Meanwhile, the shaft is where these lobes are mounted, and its rotation is what allows them to move. Connecting the two components are a series of rocker arms. The camshaft is connected to the car’s crankshaft through a timing chain or belt, sometimes alongside a system of gears. The crankshaft – sometimes simply referred to as the crank – it the part of a car responsible for transforming the linear energy produced in the engine to the rotational energy that ultimately drives the wheels.
The camshafts of modern cars also feature sensors, which we’ll return to in more detail later on.
Where is the Camshaft located?
Cars have either one camshaft for all the engine cylinders, or one for the intake and one for the exhaust valves. Some engines, such as V6 or V8, even have four camshafts.
They’re usually located beneath the cylinders of your vehicle’s engine. On ‘V’ type engines, the camshaft is positioned at the base, whereas in flat engines they’re found between the cylinder banks.
Types of Camshaft
There are two main type of camshaft:
- Flat Tappet
Flat tappet camshafts feature an almost flat bottom on their lifters. When the rotating lobes press up against this bottom, it can sometimes dig in, causing friction. They’re less expensive than roller cams, but tend to be less reliable. Nonetheless, they still find a place in racing engines.
- Roller Cams
Roller cams generally feature fatter lobes, and are standard for all modern production vehicles. At the end of a roller cam lifter, as the name suggests, you’ll find a rolling cylinder, which the lobe pushes up with reduced friction as it rotates. Roller cams are more expensive, but also more reliable.
Lobe Shape
The shape of a camshaft’s lobes ultimately determines a few things:
- When the engine’s valves will open and shut
- How long the valves will remain open for
- How quickly the valves will open
Because of this, lobe shape is a surprisingly complex topic. Camshaft lobes are typically shaped like something between an egg and a teardrop; when the pointed end pushes against the lifter, this raises it and opens the valve. The exact slope and dimensions of a lobe can be adjusted to achieve optimum performance for the engine in question.
Camshaft Sensors
All modern cars feature a sensor on their camshaft; so, what does a camshaft sensor do? Its function is to monitor the rotation of the shaft, and notes when the valves are open and closed. This information is relayed to the car’s ECU, and used to help fine tune spark timing as well as injector pulse.
The sensor is typically positioned above a notched ring at the front of the camshaft. They work through a series of magnets, which produce an AC electronic signal. This signal is, in turn, picked up by another sensor – the position sensor – which detects when the piston reaches its farthest point from the crankshaft.
If there’s something wrong with your car’s camshaft sensor, you can expect to experience the following symptoms:
- Check Engine Light Illuminates
One of the first signs to look out for is your car’s check engine light switching on. The light is connected to your car’s on board computer, and receives a signal when something goes wrong. If your light illuminates, be sure to consult a trusted mechanic as soon as possible – even if your car seems to be driving normally, take it to be diagnosed at your local auto store.
- Your Car is Driving differently
You know how your car feels to drive normally, so chances are you’ll know something’s not quite right when you notice differences in its performance. These differences could be the result of a faulty cam sensor affecting the entry and exit of fuel and air into the engine. Differences to watch out for include:
- More frequent stalling
- Rough idling
- A drop in fuel economy
- Slowed acceleration
- A drop in engine power
- Your Car won’t start
If your car won’t start at all, a faulty camshaft sensor is one possible culprit. As the sensors deteriorate, the signal it sends out to your car’s engine control unit (ECU) becomes weaker and weaker, until eventually it receives no signal at all. Without this signal, the engine will no longer run.
- Jerking
If the camshaft positioning sensor becomes faulty, you’ll likely notice a jerky sensation as you drive along. This is because the engine loses power when the sensor is not functioning correctly.
- Problems shifting Gear (Automatic Vehicles)
When a camshaft sensor is faulty in an automatic vehicle, you might find that the car locks its transmission into a single gear. This can be temporarily fixed by switching the engine off and restarting the car, but since a broken camshaft sensor can cause ignition problems, this risks exacerbating the situation.
What Else Can Go Wrong?
Although the most common problem you can experience with a camshaft is a faulty sensor, it’s worth knowing what else could cause this vital component to malfunction or fail:
- Worn Lobes
Over time, the cam lobes can become worn down – this means they no longer open the valves as wide as they once did. Worn lobes can result in poor engine performance and misfiring.
- Broken Camshaft
It’s also possible for the camshaft to fail altogether – if this happens you can expect your engine to cut out entirely. This failure can usually be attributed to the camshaft seizing.
- Incorrect Break-in Lubricant
If the incorrect lubricant has been put on the lobes upon installation, the camshaft can wear at a faster rate than it should. Unfortunately, this problem won’t be obvious straight away.
- Coil Binding
Sometimes, springs become solidly compressed during full camshaft lift. The solid metal can prevent motion in the drivetrain, and cause further problems.
Keeping Your Car’s Camshaft In Good Condition
As with many mechanical problems, prevention is far better than cure when it comes to keeping your camshaft in good working order. There’s plenty you can do to help extend the lifetime of this important component:
- Regular Oil Changes
The single best thing you can do to help preserve your car’s camshaft is to perform regular oil changes, using a good quality oil. You should change your car’s oil every 10,000 miles.
- Avoid Overheating
Preventing your car from overheating will also minimise unnecessary strain placed on the part. You can help to prevent overheating by:
- Keeping the oil level topped up
- Keeping an eye on your temperature gauge while driving in warm weather
- Clean the car regularly, to keep the radiator free from debris
- Try to avoid the heat of rush hour traffic
Repairing a Faulty Camshaft
If you suspect your car’s camshaft sensor is faulty, take the car to be checked by a trusted mechanic as soon as possible. To replace a camshaft sensor, you can expect to pay between $90 and $300, depending on the make and model of your car – including both parts and labor. The repair should not usually take longer than a day.
On the other hand, replacing the whole camshaft can be considerably more expensive. You should be able to get hold of a new component for between $200 and $300 depending on the make and model of your car. Labor costs will also vary, but you can expect to spend around $600 to $1,000.
Sources:
- How Camshafts Work – HowStuffWorks
- What Does a Camshaft Do? – DoItYourself
