Cylinder 4 Misfire Detected
What it means
The engine computer has found that cylinder 4 fails to complete combustion over many engine cycles. On inline four-cylinder engines this cylinder is usually at the opposite end from cylinder 1, and the most common cause is an ignition part or injector serving it.
Related lights
Dashboard lights that may come on with this code.
Symptoms4
- Noticeable shaking at idle or when the A/C is switched on.
- Slow acceleration.
- Check engine light on, possibly flashing.
- Fuel smell from the exhaust.
Possible causes6
- Worn or fouled spark plug in cylinder 4.
- Weak ignition coil for cylinder 4, or a coil shared by cylinders 1 and 4 on some four-cylinder engines.
- Clogged or faulty cylinder 4 injector.
- Damaged wiring or connectors serving this cylinder.
- Vacuum leak near the cylinder 4 intake runner.
- Low compression in the cylinder (less common).
How to diagnose5
- Read the misfire counters; if P0301 appears with P0304, check whether the engine uses one coil for cylinders 1 and 4.
- Inspect the cylinder 4 plug and compare it with plugs from healthy cylinders.
- Swap the cylinder 4 coil with another cylinder, clear the codes and see whether the code moves.
- Check the injector and its signal with suitable equipment, or swap it with another injector if access is easy.
- Have a compression test done if the misfire remains.
How to fix6
- Replace the spark plug, or the full set if it is due.
- Replace the ignition coil the misfire followed.
- Repair damaged wiring or connectors.
- Clean or replace the injector.
- Fix the vacuum leak or low compression if found.
- Clear the codes and drive to confirm the code does not return.
Repair cost
In Saudi riyals; the highlighted part is the expected range for this fault.
In the Saudi market: SAR 150–1,500 (≈ USD 40–400)
Our prices come from the Saudi market, converted at a fixed rate (SAR 3.75 per USD). Prices in your country may differ a lot, so we show the cost level.
The cost stays low with a plug or coil, rises with an injector or an intake leak repair, and can exceed this range if compression is low.
Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026
Frequently asked questions
Why did P0301 and P0304 appear together?
Some four-cylinder engines use one coil to fire cylinders 1 and 4 together, so that coil or its wire is the first suspect. If each cylinder has its own coil, look for another shared cause.
Is one new spark plug enough?
It is if the other plugs are fairly new. If they are all old, replace the set, because worn plugs strain the coils and cause new misfires.
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