P0287
Universal (All Makes) Vehicle (OBD-II)
Severity: ModerateWhat Does This Error Mean?
P0287 means Cylinder 9 is not contributing its expected share of engine power — a cylinder contribution or balance fault. This code only applies to engines with 9 or more cylinders — primarily V10 and V12 engines. The ECM detects the fault by measuring crankshaft speed changes after each cylinder fires. If Cylinder 9's contribution is lower than expected, P0287 is stored. Symptoms include noticeable engine vibration (more detectable on large-displacement engines), rough idle, reduced power, and fuel economy drop.
Affected Models
- All vehicles 1996+ with 9 or more cylinders
- Common in Ford F-250/F-350 with 6.8L V10
- Common in Dodge Viper V10 engines
- Common in V12 luxury vehicles from BMW, Mercedes-Benz, and Audi
Common Causes
- Fouled or worn spark plug on Cylinder 9 causing weak or incomplete combustion
- Failing ignition coil on Cylinder 9 producing insufficient spark energy
- Partially clogged fuel injector on Cylinder 9 not supplying enough fuel
- Low compression in Cylinder 9 from worn piston rings, valves, or a head gasket failure
- Small vacuum leak near the Cylinder 9 intake runner causing a lean condition in that cylinder
How to Fix It
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Inspect and replace the Cylinder 9 spark plug. On V10 and V12 engines, rear-bank plug access is notoriously difficult and often results in these plugs going the longest without service. Compare Cylinder 9's plug to front-bank plugs — condition differences reveal neglect.
On Ford's 6.8L V10, spark plug replacement is a major job due to access constraints — it's common to have the full set done at once to avoid repeat labor costs.
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Swap the Cylinder 9 ignition coil with a coil from a different cylinder. Clear the codes and drive. If the balance fault follows the coil to its new location, the Cylinder 9 coil has failed. Replace it.
This swap test applies the same diagnostic logic on a V10 or V12 as on any smaller engine — it's still the most cost-effective first step.
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Have the Cylinder 9 injector professionally flow-tested. Injectors on high-mileage V10 engines are often clogged with fuel varnish deposits — professional ultrasonic cleaning can restore flow at a fraction of replacement cost.
Flow testing is especially worthwhile on V10 engines where injector replacement costs more than on smaller engines.
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Inspect the intake manifold area near Cylinder 9 for vacuum leaks, particularly around manifold end caps and rear vacuum port connections. Large V10 and V12 intake manifolds have more potential leak points than smaller engines.
A professional smoke test is highly recommended for large-displacement engines where a vacuum leak can be hard to locate by ear or with carburetor cleaner.
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Perform a compression test on all cylinders. Low compression on Cylinder 9 alone points to internal wear requiring professional assessment. On V10 and V12 engines, internal engine repairs are significant investments — gather all the diagnostic information before deciding on a repair path.
Always follow low compression with a leak-down test to pinpoint the cause: rings, intake valve, exhaust valve, or head gasket.
When to Call a Professional
A contribution fault on a V10 or V12 engine is more serious than on a smaller engine — the cost of cascading damage is much higher. If basic tune-up parts don't resolve P0287, have a mechanic perform a compression and leak-down test on Cylinder 9 promptly. Internal engine repairs on V10 and V12 engines are expensive — catch problems early.
Frequently Asked Questions
Can a V10 run okay on 9 cylinders?
It will still move, but a V10 with one weak cylinder is noticeably rough compared to normal. You'll feel vibration at idle that isn't typical for a smooth V10. The other cylinders carry extra load to compensate, increasing wear. Fix it before the contribution fault becomes a full misfire.
Is spark plug replacement on a V10 a DIY job?
It depends on the specific engine. Ford's 6.8L V10 spark plug replacement requires some patience and the right tools, but it is a DIY job for a capable home mechanic. However, the rear spark plugs are much harder to access than the fronts — many owners have a shop do the full set to save time and avoid damaging plug threads.
How much does it cost to fix P0287?
Spark plugs (full V10 set): $150–$400 installed. Ignition coil: $60–$200 installed. Injector cleaning: $50–$100 per injector. Injector replacement: $200–$600 installed. Engine internal work: $2,000–$6,000+.