P0303

Cylinder 3 Misfire Detected

Car Fault Codes Powertrain

Can you still drive? With care, short trips only

Typical cost Under SAR 5,000

What it means

The computer detected weak or intermittent combustion in cylinder 3. Diagnosis should always start with the ignition and fuel parts serving that cylinder before suspecting bigger problems.

Symptoms4

Engine shake at idle and at traffic lights.
Partial loss of power.
Check engine light on or flashing.
Uneven engine sound.

Possible causes6

Weak ignition coil on cylinder 3.
Worn or incorrect spark plug in cylinder 3.
Injector on cylinder 3 not spraying properly.
Loose connector or broken wire near the cylinder.
Vacuum leak near the cylinder intake runner.
Low compression from a burnt valve or ring wear (less common).

How to diagnose and fix5

Test the coil by swapping it to another cylinder and watching whether the code moves.
Inspect the spark plug and compare it with the others.
Check the injector and coil connectors for a firm, clean fit.
Test the injector or swap it with another cylinder.
Request a compression test if nothing changes.

Repair cost

0–500

500–2,000

2,000–5,000

5,000+

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost stays low for a coil or plug, and increases if cylinder head repair is required.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.

Frequently asked questions

I replaced the spark plug and the code is still there. What next?

Swap-test the coil, then the injector. If the misfire still stays on cylinder 3, the problem is likely mechanical and needs a compression test.

Should I replace all coils at once?

Not necessary if only one coil is proven bad, although some owners of high-mileage cars prefer to replace the full set.

This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.

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