The camshaft is a rotating shaft with egg-shaped lobes that push the engine's valves open at exactly the right moment. It choreographs when air enters and exhaust leaves each cylinder.
Animated: how a Camshaft actually works
🔧 How It Works, Step by Step
1
Spin with the engine
The camshaft is driven by the crankshaft through a timing belt or chain at exactly half crank speed.
2
Lobes lift the valves
As each egg-shaped lobe rotates, its high point pushes a lifter or rocker to open a valve.
3
Springs close the valves
As the lobe rotates past, the valve spring snaps the valve shut and seals the cylinder.
4
Repeat in sequence
The lobes are staggered so intake and exhaust valves open in the correct order for every cylinder.
🧩 The Key Parts
Cam lobes
The offset bumps that convert rotation into valve-opening motion.
Cam journals
Bearing surfaces that let the camshaft spin smoothly in the head or block.
Camshaft sensor
Tells the computer camshaft position so it can time fuel and spark.
Cam gear or sprocket
Connects the camshaft to the timing belt or chain from the crankshaft.
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The 50 most common check engine codes with likely cause and DIY fix cost. Sent once.
🩺 Signs of a Failing Camshaft
Ticking or tapping from the top of the engine
Rough idle or misfires
Check engine light for cam timing or sensor
Loss of power in a certain rev range
Hard starting
⚠️ Common Problems
Worn cam lobes
Flattened or worn lobes fail to open the valves fully, causing weak power and a tapping noise.
Camshaft sensor failure
A bad sensor confuses the computer about engine position, triggering misfires, stalling, or hard starts.
Timing skip
A stretched chain or worn belt lets the camshaft fall out of sync with the crankshaft, upsetting valve timing.
💰 Cost to Fix
$200-$3,000typical range to repair or replace, parts and labor
❓ FAQ
What is the difference between a camshaft and crankshaft?
The crankshaft is driven by the pistons and makes power, while the camshaft is driven by the crankshaft and opens the valves at the right time.
What is DOHC vs SOHC?
DOHC uses two camshafts per cylinder bank, one for intake and one for exhaust valves, while SOHC uses a single camshaft to work both.
How much to replace a camshaft sensor?
A camshaft position sensor usually costs $150 to $400 to replace, much less than the camshaft itself.