What Are Cam Phasers? And How Does It Work?

Cam phasers and engine starters go together – and much more often than one would think. Their mechanisms serve as the turning point of a typical combustion process, ensuring the intake valves open and close properly for optimal performance and ignition.

If you wonder what cam phasers do exactly, my guidelines would be a great starting place; keep scrolling for more info.

What Is A Cam Phaser?

Camshaft phasers (VVT Solenoid/Variable Valve Timing system) are installed in the internal combustion tank to control the camshaft timing and regulate the closing and opening of the engine/exhaust valves depending on your power or fuel efficiency needs.

Cam Phaser
Cam Phaser

You would find these phasers at the tip end of a camshaft, driven by the belt or timing chain of the engine block. This design allows the car system to adjust the camshaft’s angular position much easier for optimal valve timing, paving the way for better emissions, fuel economy, and engine performance.

How Do Cam Phasers Work?

How Do Cam Phasers Work

Modern vehicle sensors will input data to the ECU, which commands camshaft timings when necessary. Your camshaft phaser will adjust the cam’s position accordingly to either retard or advance the timings of the valves. 

Here is a more detailed breakdown of the process:

  • Various sensors in the vehicle models (ex: load, engine speed, throttle response) sends data readings to the ECU. Based on these inputs, the ECU determines the best camshaft positions for your car’s current operation circumstances.
  • The ECU will then send commands for camshaft timing changes to the phaser. Upon this request, the phaser rotates slightly to change the position of the camshaft. Valve timings are altered as a result – which means the valve covers might close/open later or earlier than usual within the combustion cycle.

Such flexibility proves practical for cars undergoing vastly different driving conditions. Changing from high to low RPM or vice versa will also be a piece of cake.

Causes and Symptoms of Cam Phaser Failure

Cam phaser malfunctions directly result from wrong oil thickness, dirty engine oil, and damaged camshaft gears/ sockets. They manifest in notable symptoms such as clicking sounds, illuminated CEL, diagnostic trouble codes, performance drops, and engine failure.

1. Symptoms

Clicking Sounds

Loud knocking noises are easily the most tell-tale signals.

When the cam phasers wear out, they fail to connect properly to the cylinder heads and, as such, cannot deliver the engine its proper oil amount. 

With a severe lack of oil pressure, the engine can only give off weak growls instead of launching into full operations – hence all the excessive phaser noises.

The Engine’s Power Loss

Since the oil pressure is affected, it is natural to assume that power loss would follow suit. Your car will encounter at least one of the following issues:

  • Difficulties with car starting
  • Inaccurate acceleration
  • Engine misfires

The CEL (Check Engine Light) Illuminates

Since the ECU and exhaust cam phasers are connected, a failed phaser will inevitably push the ECU into a tottering or limp mode (or, long story short: the ECU fails to function properly). 

The engine fails to receive proper starting power and suffers from low RPM, sending the error codes to your car’s consoles. Triggered by these digit codes, the EL will glow to inform you of technical cam phaser issues.

Performance Drops

Reaching RPMs beyond 40 is impossible with a low-oil engine. Worse, your car will eat much more fuel than usual and torture you with non-stop vibrations throughout the way – even on smooth road surfaces. A nightmare, truly.

2. Causes

Wrong Oil Viscosities

Proper lubrication and friction are out of reach if you use thicker or thinner oil than required. 

Added by extreme temperatures (which most engines and cam phasers are exposed to), premature wear and slow responses are only to be expected! Not to mention, with the wrong viscosities, the oil pressure will also be severely affected as a result.

Contaminated Oil

Oil getting old easily gets mixed with debris, dirt, and sludge. All these build-ups lead to reduced/hampered flow of oil, which naturally damages the cam phaser’s well-being. 

Hence, you should always keep track of your oil change intervals. Even though certain oils (like synthetic ones) do not require tops or swaps as frequently as other oil types, they should still be checked at least once per month for unusual signals.

And, while at it, do not forget oil filter replacements, either. Only then can the fluid remain 100% fresh.

Damaged Cam Drive Sprockets or Timing Gears

Cam sprockets and gears need frequent lubrication, sure. But excessive lubrication is a different story altogether, which destroys their internal parts prematurely and eventually troubles the cam phasers as well.

Once fixing the gears/sprockets, remember to add some friction modifiers or use higher-quality oil to reduce the wear risks.

How Much Does It Cost to Replace Cam Phasers? 

Cam phaser replacement costs fluctuate from $800 to $2500. Since the process is complex, time-consuming (four hours), and requires lots of expertise, these expensive repairs are totally justified.

How Long Can You Drive With A Faulty Phaser?

It is unpredictable: the mileage can range from a few hundred miles to as long as 4,000-5,000 miles. And due to that unpredictability, ignoring the issue is like playing with fire: you can never guess when the engine damage will eventually catch up. 

Make a trip to an automobile shop as soon as possible.


Issues with cam phasers – while not difficult to fix – can leave detrimental consequences if ignored for too long. Hence, I cannot stress enough the importance of regular inspection and maintenance; keep a consistent schedule, and write to me if you still need help on cam phaser damage.

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Daniel Barker


Daniel Barker was introduced to racing in 2006 when he experienced his first track day on his Suzuki sv650. With more than 15 years of experience on his track. Daniel is known as for his high-energy riding, drifting, precision stoppies and technical riding ability on virtually any motorcycle.

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