How to Tell If a Camshaft Is Bad

You can usually tell a camshaft is bad by a combination of symptoms—persistent misfires, rough idle, loss of power especially at higher RPM, top-end ticking/knocking that follows engine speed, metal in the oil, and check-engine lights for cam/crank correlation or variable valve timing issues—then confirm with inspection and measurements of cam lobes, followers/lifters, and timing alignment. In modern engines, distinguishing cam wear from variable valve timing (VVT) or lifter failures is key, so a methodical diagnosis using scan data, oil inspection, and, if needed, visual/mechanical checks is essential.

What it looks and sounds like

The following list outlines common symptoms drivers and technicians notice when a camshaft or its related components are failing.

• Rough idle and persistent misfire, often cylinder-specific, that doesn’t go away with new plugs/coils.
• Noticeable power loss and poor acceleration, especially above midrange RPM where valve lift/duration matter most.
• Top-end ticking, clatter, or knocking from the valve cover area that rises with RPM; may be sharper with flat-tappet wear or rhythmic with a collapsed roller lifter.
• Check-engine light with codes such as P0300–P030X (misfires), P0010–P0024 (VVT solenoid/performance), or P0016–P0019 (crank/cam correlation).
• Hard starts, backfiring through intake or exhaust, and unstable idle vacuum (vacuum gauge needle flutter).
• Oil contaminated with metallic sparkle or ferrous debris in the filter; sometimes low or fluctuating oil pressure.
• Abnormal fuel economy and emissions test failures from poor valve timing and cylinder efficiency.

Any one symptom can have other causes, but multiple signs together—especially misfires plus valvetrain noise and correlation codes—strongly point toward camshaft or lifter-related trouble.

What technicians check first

Before tearing into the engine, professionals use non-invasive checks to separate camshaft problems from lookalikes and to gather evidence.

1. Scan for codes and data: Review freeze-frame, misfire counters, cam/crank correlation, VVT commanded vs. actual angle, and oil temperature/pressure if available.
2. Listen and locate: Use a mechanic’s stethoscope on valve covers, front timing cover, and intake to pinpoint top-end noises and distinguish them from bottom-end knocks.
3. Oil check: Inspect level, smell for fuel dilution, and cut open the oil filter to look for shiny metal or needle bearing fragments (roller lifter failure clue).
4. Vacuum and backpressure: A manifold vacuum test can reveal valve timing issues; exhaust backpressure checks rule out a clogged catalytic converter mimicking power loss.
5. Basic timing sanity check: Verify timing marks alignment where accessible and look for slack in timing chains/belts indicating stretch or skipped teeth.
6. TSBs and patterns: Check technical service bulletins for known lifter/phaser issues (e.g., GM AFM/DOD lifter collapse, Ford/Chrysler cam phaser noises).

If these checks implicate the valvetrain or timing rather than ignition or fuel systems, the next step is targeted mechanical verification.

How to confirm camshaft damage

Definitive confirmation comes from visual inspection and measurement. These steps require mechanical access and, ideally, service specifications.

1. Remove the valve cover(s): Inspect cam lobes and followers/rockers for scuffing, pitting, spalling, blueing (overheat), and lobe “rounding” or edges worn sharp.
2. Check lifters: Ensure roller lifters spin freely with intact needles; flat-tappet lifters should rotate in their bores. Any lifter failure can quickly destroy a cam lobe.
3. Measure lobe lift: Use a dial indicator on the valve tip, rocker, or pushrod to compare total lift to spec; significant loss of lift or uneven lift between cylinders indicates lobe wear.
4. Assess base circle and runout: Mic the lobe base-circle for uniformity; check cam runout and end play against service limits.
5. Evaluate bearings and journals: Look for scoring or seized cam bearings; verify oil feed holes are not plugged and that there’s adequate top-end oiling.
6. Correlation and waveform test: With an oscilloscope, compare crank and cam sensor signals for phase shift; excessive chain stretch or a worn keyway can mimic or accompany cam issues.
7. Compression and leak-down: Cylinder(s) with low compression that improves with a small increase in duration (via VVT test) or shows no sealing faults can point to lift/timing loss.
8. VVT phaser function: Command phasers with a scan tool; sluggish or stuck phasers, or large commanded-vs-actual error, can create cam timing symptoms without a bad cam lobe.

Finding a damaged lobe, collapsed lifter, or out-of-spec lift is conclusive; correlation errors without visible wear often implicate timing components or phasers instead of the cam itself.

Common causes of camshaft failure

Understanding why camshafts fail helps prevent repeat failures after repair.

• Oil starvation or contamination: Low oil, fuel dilution (common on short-trip DI engines), clogged pickup, or restricted oil passages.
• Incorrect oil specification: Using low-ZDDP oil in older flat-tappet engines accelerates wear; ignoring OEM viscosity/additive requirements can impair VVT and lubrication.
• Lifter failure: Roller needle bearing collapse or flat-tappet scuffing destroys lobes rapidly.
• Timing faults: Chain/belt failures or phaser malfunctions causing impact or misalignment.
• Valve spring issues: Excessive spring pressure, coil bind, or over-rev/valve float causing lobe and follower damage.
• Improper installation/break-in: Skipping break-in on flat-tappet cams, dirty assembly, or misaligned bearings.
• Debris and corrosion: Metal from other failures, poor filtration, or long storage with moisture intrusion.

Addressing the root cause—often oiling, lifters, or timing components—is as important as replacing the camshaft itself.

When it isn’t the camshaft

Many problems mimic a “bad cam.” This list highlights common impostors to rule out early.

• Ignition and fuel faults: Coils, plugs, injector issues, low fuel pressure, or a failing MAF creating misfires and power loss.
• Exhaust restriction: A clogged catalytic converter limits high-RPM power similar to low lift.
• Hydraulic lifter or lash adjuster collapse: Noisy top-end and misfires without lobe damage.
• Rocker arm/fulcrum failures: Particularly on some OHC designs (e.g., lost roller followers).
• VVT solenoid or phaser issues: Stuck or slow response causing timing errors and codes.
• Timing chain stretch or slipped belt: Alters cam timing while the cam itself remains intact.
• Vacuum leaks or EGR malfunctions: Rough idle and misfires not related to cam wear.

Eliminating these with quick tests saves time and avoids unnecessary engine teardown.

Repair decisions, parts, and typical costs

Once confirmed, repairs range from lifter/cam replacement to comprehensive timing and oiling updates; costs vary widely by engine design.

• Camshaft and lifter set: Common on OHV V8s; parts $300–$1,200, installed $800–$2,500 depending on access.
• OHC/DOHC cams and followers: More labor-intensive; timing components often required; $1,500–$4,500 installed.
• VVT phasers/solenoids and timing sets: Frequently replaced together; $600–$1,800 depending on engine.
• Cam bearings and machine work: If journals/bearings are damaged, costs rise and engine removal may be required.
• Full engine replacement or rebuild: If debris or bearing damage is widespread; $3,500–$8,000+ for long blocks.

Budget for oil and filter, gaskets, new lifters with any new cam, and meticulous cleaning; skipping related parts often leads to repeat failures.

Safety, installation, and prevention

A few practices can prevent cam failure and ensure a successful repair.

• Use the exact oil spec and change on time; consider shorter intervals for DI engines with fuel dilution or heavy stop‑and‑go use.
• Break-in procedures: For flat-tappet cams, use break-in lube and high-ZDDP oil; run at 2,000–2,500 RPM for 20–30 minutes; avoid high spring pressures during break-in.
• Replace lifters and inspect springs, rockers, and pushrods when installing a new cam.
• Prime the oil system before first start; verify top-end oiling quickly after startup.
• Follow torque/angle specs and cam timing procedures; lock phasers where required by the OEM.
• Keep the engine clean during service; cut open the used filter after the first post-repair oil change to confirm no ongoing wear.

Preventive maintenance and proper assembly steps are the cheapest insurance against another cam-related failure.

FAQs

Can a bad camshaft ruin the engine?

Yes. A failed lobe or lifter sheds metal that circulates through bearings and turbochargers (if equipped). If metal is found, inspect oil clearances and consider a deeper repair than just a cam swap.

Will the check-engine light always come on?

No. Mechanical wear can exist without a code, but correlation or VVT performance codes are common when timing is affected. Noise plus misfire without obvious ignition/fuel causes warrants a mechanical check.

How do I tell cam wear from a bad lifter?

A collapsed or stuck lifter often causes one-cylinder misfire and loud tick; if lobe lift measures to spec and swapping the lifter fixes the issue, the cam may be fine. Flattened lobes show reduced lift and typically damage the mating lifter.

Is a vacuum gauge still useful on modern engines?

Yes. Unstable or lower-than-normal steady vacuum can indicate valve timing problems, though scan tool data and VVT tests add clarity.

Summary

A bad camshaft reveals itself through a pattern: persistent misfires and top-end noise, loss of power, debris in the oil, and scan data showing timing discrepancies. Confirm by inspecting lobes and lifters, measuring lift, and verifying cam/crank correlation and VVT operation. Rule out mimics like ignition faults, lifter collapse, phaser issues, and timing chain stretch. If the cam is bad, replace related components, address the root cause (usually oiling or lifter failure), and follow strict installation and break-in practices to prevent a repeat.

What does a bad camshaft sound like?

A bad camshaft typically produces a ticking, tapping, or rattling noise coming from the top of the engine, which may get louder with acceleration. This sound results from excessive wear or damage to the camshaft lobes or lifters, causing increased clearance and metal-on-metal contact. In severe cases, you might also hear grinding, experience misfires, engine problems, and potentially find metal shavings in your oil. 
Sounds to listen for:

• Ticking or Tapping: A persistent, rhythmic ticking or tapping sound from the top of the engine is a common first sign of a worn or damaged camshaft. 
• Rattling or Clacking: Unusual rattling or clacking noises, possibly noticeable at startup or while the engine runs, can indicate a failing camshaft actuator. 
• Grinding: In advanced stages of camshaft failure, you might hear grinding sounds, which are a more serious indicator of internal damage. 
• Misfires: A worn camshaft lobe can cause valves to not open and close properly, leading to engine misfires and rough running. 
• Popping: A soft popping sound from the air intake could signal a camshaft-related issue. 

Other signs of a bad camshaft:

• Engine Misfires: Incomplete combustion due to improper valve operation can lead to engine misfires and a rough idle. 
• Poor Engine Performance: Worn camshaft lobes lead to low compression and a general loss of engine power and sluggish acceleration. 
• Check Engine Light: A faulty camshaft can trigger the “check engine” light, often related to misfires or timing issues. 
• Difficulty Starting: A problematic camshaft can affect the camshaft position sensor’s accuracy, leading to hard starting or prolonged cranking. 
• Metal Shavings in Oil: A severe problem can cause metal shavings to appear in your engine oil, indicating significant wear. 

How do you inspect your camshaft?

Place the camshaft on Vblocks. Position the dial indicator on the center bearing journal and slowly rotate the camshaft. If the dial indicator shows runout (a 0.002-inch deviation), the camshaft is not straight. A bent camshaft must be replaced.

How do you know if you have a bad camshaft?

The key symptoms of a bad camshaft include ticking or tapping noises, poor engine performance, engine misfiring, a check engine light, and visible wear or damage. Recognising these signs early is crucial to prevent more severe engine issues.

Will a car run with a bad camshaft?

No, you should not drive with a bad camshaft. A failing camshaft can cause severe engine damage, poor engine performance, and potential stalling, which can lead to accidents. If you suspect you have a bad camshaft, it is best to stop driving the vehicle immediately and have it towed to a qualified mechanic for inspection and repair to avoid further, more expensive damage. 
Why you shouldn’t drive with a bad camshaft:

• Serious Engine Damage: Continued use can cause severe, costly damage to other engine parts. 
• Poor Performance: Expect issues like a rough or lopey idle, lack of power, and poor fuel economy. 
• Stalling: The engine can stall unexpectedly, putting you and others at risk of an accident. 
• Misfires and Incomplete Combustion: A worn camshaft can cause valves to open incorrectly, leading to misfires and unburnt fuel in the exhaust system, which can damage the catalytic converter. 
• Increased Risk: The unpredictability of a failing engine makes it dangerous for both you and other motorists. 

What to do instead:

• Stop Driving: As soon as you notice symptoms, stop using the vehicle. 
• Get it Towed: Have your car towed to a qualified mechanic. 
• Consult a Technician: A certified technician can properly diagnose the issue and recommend the necessary repairs to avoid further damage.