What a Bad Camshaft Looks Like: Visual Signs, Causes, and How to Confirm

A bad camshaft typically shows visibly worn or flattened lobes, scoring and pitting on the lobe surfaces and journals, blue/black discoloration from overheating, cracks or chips, and sometimes a bent shaft or damaged timing gear/dowel. If you’re inspecting one, look for asymmetrical lobe shapes, rough or streaked surfaces, and metal debris in nearby components; these visual cues, paired with measurements, confirm whether the cam is beyond service.

Key visual indicators on the camshaft itself

When the camshaft is accessible (under a valve cover in OHC engines or during teardown in cam-in-block designs), several telltale signs can identify damage. Focus on the lobes, journals, thrust surfaces, and drive gear/dowel areas.

• Flattened or “wiped” lobes: The lobe nose is rounded off, the lobe’s peak height is visibly reduced, or the lobe looks asymmetrical compared with its neighbors.
• Pitting and spalling: Small craters or flaking on the lobe or journal surface from surface fatigue or contaminated oil.
• Scoring and galling: Longitudinal scratches, streaking, or smeared metal on lobes or journals from oil starvation or debris.
• Discoloration (blue, purple, or black): Heat “blueing” signals overheating or lubrication failure; often accompanies galling.
• Ridges or step-wear: Noticeable steps at the lobe’s edges or on the nose/heel, indicating uneven contact or taper loss.
• Cracks or chips: Visible fractures at lobe edges, oil holes, keyways, or dowel pin areas; use bright light and magnification.
• Loss of lobe taper/crown witness marks: Flat-tappet cams should show a slight diagonal polish pattern; a straight or patchy pattern often means improper rotation and accelerated wear.
• Bent or out-of-true shaft: Witness rub on one side of journals or measurable runout; sometimes visible as uneven contact patterns.
• Excessive thrust-face wear: Grooves or heavy wear on the cam’s thrust surfaces (where applicable).
• Rust and corrosion: Pits and scale that disrupt surface finish, especially after long storage without oil.

Any combination of these marks—especially flattened lobes, scoring, and discoloration—strongly indicates a bad camshaft. The pattern of damage can also hint at the root cause, such as lubrication failure or incorrect valve train setup.

What related parts look like when the cam is failing

Camshaft damage rarely occurs in isolation. Inspect the rest of the valvetrain and timing components; their condition can corroborate a failing cam and point to the cause.

• Lifters/followers: Flat-tappet lifters may have a concave face or pitting; roller followers may show flat spots, seized rollers, chipped needles, or uneven wear.
• Rocker arms and cam followers: Scuffed pads, galling, and off-center contact patterns signal cam or geometry problems.
• Valve tips and springs: Pecked or mushroomed valve tips, broken or heat-discolored springs indicate overstress or poor lubrication.
• Cam bearings: Scored, wiped, or heat-discolored bearing surfaces point to oiling issues.
• Oil and filter: Metallic glitter in oil, magnetic “fur” on drain plug, or loaded filter pleats suggest significant cam/lifter wear.
• Timing gear/chain/belt and cam gear or phaser: Hooked teeth, excessive slack, metal dust, or a VVT phaser with excessive play or sludge contamination.

If these components show distress—even before obvious lobe damage appears—the cam may already be compromised, and continued operation risks accelerated engine wear.

Operational clues that prompt a visual inspection

While the question is about appearance, symptoms often trigger the inspection that reveals the damage. These signs suggest it’s time to look under the cover.

• Persistent valvetrain tick/clatter, especially changing with RPM or load.
• Misfires, rough idle, loss of power, popping through intake/exhaust, or low manifold vacuum.
• Metal in oil, oil pressure warnings, or rapid oil darkening after service.
• OBD-II codes such as P0300–P030X (misfire), P0010–P0017 (VVT/cam correlation), or P0340–P0345 (cam sensor circuit).

These operational clues justify a close visual and measurement-based inspection to confirm camshaft condition and prevent further damage.

How to inspect a camshaft safely and correctly

Basic on-engine checks

You can spot many issues without removing the cam. With the valve cover off (OHC) or lifters/rockers exposed (OHV), compare lobes and follower motion carefully while rotating the engine by hand.

1. Disconnect the battery and follow service manual procedures to access the valvetrain safely.
2. Check for adequate oiling to the cam/followers; dry areas are a red flag.
3. Rotate the crank by hand (correct direction) and watch valve/follower travel across cylinders; a lobe with notably less lift stands out.
4. Visually compare lobe shapes and surface finish under bright light; use a mirror and magnifier for the back rows.
5. Inspect followers/rockers for pitting, flat spots, or skewed contact patterns.
6. Check timing chain/belt slack and gear condition; note any metal dust or abnormal wear.
7. Document findings with photos and, if possible, measure valve lift variation with a dial indicator.

On-engine checks can quickly reveal obvious failures like wiped lobes or seized rollers. Avoid cranking a dry valvetrain, and maintain timing alignment marks if you plan further disassembly.

Precision off-engine measurements

If the cam is removed, measurements can confirm wear and straighten the repair plan. Always compare to the vehicle’s service specifications.

• Lobe lift: Measure lobe nose and base circle with a micrometer; lift equals nose diameter minus base-circle diameter. Compare to spec and to other lobes.
• Journal diameters and out-of-round: Mic the journals and check against specs; excessive wear or taper indicates bearing issues.
• Runout (bend): Support the cam on V-blocks and check with a dial indicator; typical max runout is roughly 0.001–0.002 in (0.025–0.05 mm), but verify the exact spec.
• Lobe taper and follower crown (flat-tappet systems): Expect a slight intentional taper (~0.0005–0.0015 in / 0.013–0.038 mm). A lost taper promotes rapid wear.
• Surface inspection: Use bright light and dye penetrant (if available) to find cracks; check for pitting, spalling, and heat discoloration.
• Oil passages: Ensure oil feed holes are unobstructed; sludge or varnish indicates lubrication problems.

If measurements fall outside spec or any lobe shows pitting, spalling, cracks, or heat damage, the cam should be replaced. Replace lifters/followers as a set with a new cam to prevent immediate re-failure.

Common causes of camshaft damage (and what they look like)

The wear pattern often reveals the root cause. Matching the look to the likely cause helps prevent repeat failures after repair.

• Oil starvation or low pressure: Blue/purple discoloration, galling, and heavy scoring on lobes/journals.
• Contaminated or degraded oil: Random pitting/spalling and widespread fine scoring.
• Incorrect oil chemistry (flat-tappet cams needing ZDDP): Rapid lobe “wipe,” concave lifter faces.
• Excessive spring pressure/coil bind: Broken or chipped lobe noses, heat marks on spring coils.
• Improper break-in (flat-tappet): Early lobe wear with poor diagonal witness pattern and metal in oil.
• Geometry/lash errors: Localized lobe edge wear, uneven rocker pad polish, pecked valve tips.
• Misaligned cam bearings: Localized journal scoring and hot spots.
• Overheating: General blueing, varnish, and potential warping/runout.
• Debris from other failures: Random deep gouges and scoring paths across multiple lobes.
• Timing failure or phaser damage: Broken dowel/key, chipped gear teeth, sludged or loose VVT phaser with inconsistent cam timing.
• Corrosion from storage: Rust pits and flaking that quickly evolve into spalling once run.

Identifying the root cause is as important as replacing the cam; otherwise, the new components may fail prematurely under the same conditions.

When replacement is mandatory

Some conditions cannot be safely repaired with polishing or a light regrind. Use manufacturer limits, but the following are broadly disqualifying.

• Any visible cracking, spalling, or significant pitting on lobes/journals.
• Heat discoloration/blueing accompanied by galling or measurable loss of material.
• Lobe lift measurably below spec or notably uneven across cylinders.
• Journal scoring you can feel with a fingernail, or out-of-round beyond spec.
• Excessive runout/bend beyond manufacturer limits.
• Damaged keyway/dowel or chipped gear teeth; VVT phaser with excessive play.
• Roller follower damage or flat-tappet lifter concavity (replace lifters/followers with the cam).

After replacement, flush the oil system, change the filter, and follow break-in procedure (use high-zinc oil and proper RPM for flat-tappet cams). Prime the oiling system, set lash/clearances to spec, and verify cam timing and VVT operation.

Cost and repair outlook (2025)

Repair costs vary widely by engine design (OHV vs. SOHC/DOHC) and whether VVT and timing components are serviced together.

• Camshaft: About $150–$600 (flat-tappet/older OHV) to $300–$1,000+ (OHC/DOHC performance or OEM).
• Lifters/followers/rockers: Roughly $100–$600+ depending on type and count.
• VVT phasers/solenoids: About $150–$400 per phaser; solenoids $50–$200 each.
• Gasket set, fluids, incidentals: Typically $100–$300.
• Labor: Approximately 6–20 hours depending on access and timing system complexity.
• Total typical: $800–$3,500; complex DOHC/VVT timing services can exceed $4,000.

Bundling timing components (chain/belt, guides, tensioners, phasers) with the cam repair often saves on future labor and ensures a durable fix.

Summary

A bad camshaft looks worn, scored, or discolored: flattened/asymmetric lobes, pitting or galling, blue heat marks, cracks, or bent/runout issues are all red flags. Related parts—lifters, followers, rockers, bearings, and VVT phasers—often show corroborating damage or metal debris. Verify with on-engine observations and off-engine measurements against spec. If damage is confirmed, replace the cam and companion parts, address the root cause (oil, geometry, break-in, timing), and follow proper reassembly and lubrication procedures to prevent a repeat failure.

Is replacing a camshaft worth it?

Replacing a camshaft is worth it for severe wear, damage, or for performance upgrades, especially if the vehicle is otherwise in good condition and you need long-term reliability. However, if the engine itself is heavily worn, a full engine rebuild may be more cost-effective than a single camshaft replacement. 
Reasons to Replace a Camshaft

• Preventative Maintenance for a Healthy Engine: Replacing a camshaft is a good investment if the rest of your engine is in good shape, as it restores lost performance, improves fuel efficiency, and ensures longer engine life. 
• Engine Performance Upgrades: Replacing a camshaft with an upgraded one can significantly improve engine power and performance. 
• Damage and Reliability: A worn or damaged camshaft affects engine power, creates misfires, and can lead to other engine problems. A new camshaft ensures better reliability and performance. 
• Warranty Protection: A new camshaft often comes with a warranty, providing long-term assurance against defects and unexpected repair costs. 

When It May Not Be Worth It

• Extensive Engine Wear: Opens in new tabIf the camshaft is so worn that the rest of the engine is also significantly worn, it may be more practical to rebuild or replace the entire engine rather than just the camshaft. 
• Cost-Effectiveness: Opens in new tabFor older vehicles with lower resale value, the cost of a camshaft replacement may outweigh the potential benefit or value of the vehicle itself. 

Signs a Camshaft Needs Replacing

• Engine Noises: Ticking or tapping noises from the valve train. 
• Performance Issues: Reduced engine power, poor acceleration, rough idling, or engine misfires. 
• Check Engine Light: Illuminates due to issues related to valve timing or engine performance. 
• Poor Fuel Efficiency: Worn cam lobes can affect valve operation, leading to poor fuel economy. 

Important Considerations

• Associated Repairs: When replacing a camshaft, you may also need to replace other valve train components, such as lifters or rocker arms. 
• Timing: Incorrect timing during reinstallation can lead to serious engine damage, so professional help is often recommended. 

What are the 7 symptoms of a bad camshaft position sensor?

Seven common symptoms of a bad camshaft position sensor are the Check Engine light coming on, rough idling, engine stalling, difficulty starting, poor acceleration and a lack of power, bad gas mileage, and engine misfires or sputtering. 
Here’s a more detailed breakdown of the symptoms:

• Check Engine Light: This is one of the most common indicators, as the vehicle’s Engine Control Module (ECM) detects the sensor malfunction and illuminates the light. 
• Rough Idle: A faulty sensor sends incorrect data, disrupting the timing of fuel injection and spark plug ignition, leading to uneven combustion, engine misfires, and a shaky idle. 
• Engine Stalling: The engine may unexpectedly shut off while driving, especially at lower speeds or when idling, due to erratic signals from the sensor. 
• Difficulty Starting or No Start: The ECM needs accurate data from the sensor to set the proper ignition and fuel injection timing. If the sensor is bad, it can lead to a prolonged crank or a complete inability to start the engine. 
• Poor Acceleration and Lack of Power: When you accelerate, the ECM needs to precisely control the air/fuel ratio. A malfunctioning sensor provides incorrect data, leading to poor fuel delivery and inadequate combustion, making the car feel sluggish. 
• Bad Gas Mileage: Incorrect fuel injection timing from a faulty sensor can cause incomplete combustion, wasting fuel and leading to a noticeable drop in fuel economy. 
• Engine Misfires/Sputtering: An inaccurate camshaft position signal can cause the spark plugs to fire at the wrong time, resulting in engine misfires, sputtering, and poor overall engine performance. 

How do I tell if my camshaft is bad?

Symptoms of a failing camshaft include a persistent check engine light, noticeable engine misfires, rough idling, and a significant loss of power. You may also hear loud ticking or tapping noises from the engine, experience increased fuel consumption, and find metal shavings in your engine oil. A bad camshaft can also lead to difficulty starting, poor acceleration, and even engine stalling.
 
Engine Performance & Sounds

• Check Engine Light: The vehicle’s computer may detect a problem and illuminate the check engine light. 
• Rough Idle: A bad camshaft can cause inconsistent valve timing, leading to a rough or unstable engine idle. 
• Engine Misfires: Worn camshaft lobes can prevent valves from fully opening or closing, leading to incomplete combustion and cylinder misfires. 
• Loss of Power: Inefficient combustion and improper valve timing reduce the engine’s power and acceleration. 
• Loud Ticking or Tapping: Worn camshafts can create loud ticking or tapping sounds from the engine’s valvetrain. 
• Difficulty Starting: A faulty camshaft or its position sensor can disrupt the engine’s timing signals, making it difficult for the engine to start. 
• Stalling: Severe camshaft problems can cause the engine to stall, especially at low speeds. 

Other Indicators

• Increased Fuel Consumption: Poorly timed or incomplete fuel combustion leads to less efficient fuel use and increased fuel consumption. 
• Backfiring: If valves fail to close correctly, fuel can ignite outside the combustion chamber, causing backfiring. 
• Metal Shavings in Oil: A deteriorating camshaft or its bearings can shed metal debris, which you might find in your engine oil. 
• Increased Emissions: Poor combustion due to camshaft issues can lead to higher levels of exhaust emissions. 

What to Do
If you notice any of these symptoms, it’s crucial to have your vehicle diagnosed by a professional. A certified mechanic can use an OBD-II scan tool to check for trouble codes, which can help pinpoint a faulty camshaft or related components like the camshaft position sensor.

What happens if your camshaft goes out?

When a camshaft goes bad, you might notice symptoms like a check engine light, a rough idle, loss of engine power, and cylinder misfires. You may also hear a loud ticking or tapping sound from the engine. Other signs include poor fuel economy, difficulty starting, and stalling. In severe cases, metal shavings can appear in the engine oil. 
Common Symptoms of a Bad Camshaft

• Check Engine Light: The vehicle’s computer may detect a problem with the camshaft’s function, triggering the light. 
• Rough Engine Idle: Inconsistent valve timing can lead to an irregular engine operation. 
• Engine Misfires: Worn camshaft lobes can disrupt valve timing, preventing proper air-fuel mixture combustion. 
• Loss of Power and Performance: Inefficient combustion due to poor valve timing can result in reduced engine power and acceleration. 
• Loud Ticking or Tapping Noises: Worn camshaft lobes can increase valve clearance, causing noises in the valve train. 
• Engine Stalling: In severe cases, especially at low speeds or idle, a bad camshaft can cause the engine to stall. 
• Difficulty Starting: A faulty camshaft can affect the accuracy of sensor data, making it harder for the engine to start. 
• Increased Fuel Consumption: Inefficient combustion leads to less power output, making the engine use more fuel to maintain performance. 
• Backfiring: Incorrect valve timing can allow unburnt fuel to ignite outside the cylinder, causing popping sounds from the intake or exhaust. 
• Metal Debris in Oil: As the camshaft wears, it can produce metal shavings that contaminate the engine oil. 

Why These Symptoms Occur
The camshaft’s primary job is to control the timing of the engine’s intake and exhaust valves. When it goes bad, these valves may not open or close correctly, leading to: 

• Improper Combustion: Opens in new tabValves not opening or closing at the right time leads to incomplete or inefficient burning of fuel. 
• Disrupted Engine Timing: Opens in new tabThe engine’s computer relies on the camshaft for precise timing data. If this data is inaccurate, the engine can’t coordinate spark and fuel delivery properly.