Can an injector cause P0303?

Yes. If a new spark plug and coil do not help, a mechanic checks the cylinder 3 injector. A clogged or leaking injector gives the cylinder too little or too much fuel, which causes misfires.

P0303 Code: Cylinder 3 Misfire – Meaning & Causes

Q: Can I drive with code P0303?

Not if the check engine light is flashing. Stop when it is safe, because unburnt fuel can destroy the catalytic converter. If the light stays on steadily and the engine runs almost normally, drive gently to a garage.

P0303 code: misfire in cylinder 3

Fault code P0303 means the engine control module has detected misfires in cylinder 3. The mixture in that cylinder does not burn properly, so the engine runs unevenly. The most common cause is a worn or fouled spark plug, followed by the ignition coil, the injector and mechanical problems such as low compression.

Check P0303

When the code is set

The ECM uses the crankshaft position sensor to measure how smoothly the engine turns. When cylinder 3 misfires, the crankshaft slows for a moment at the point that belongs to that cylinder. When there are too many of these misfires, the ECM stores P0303; with severe misfires the check engine light flashes.

Can I keep driving?

Have it checked soon

If the check engine light flashes, stop when it is safe and do not drive on: unburnt fuel can destroy the catalytic converter. If the light stays on steadily and the engine runs almost normally, drive gently without hard acceleration and have the car checked as soon as possible. If the engine shakes badly or loses power, it is better to have it taken to a garage.

Symptoms

The check engine light is on or flashing.
The engine shakes, especially at idle.
Jerking and less power when accelerating.
Hard starting.
Higher fuel consumption.

Common causes

A worn or fouled spark plug in cylinder 3 – the most common cause.
A faulty ignition coil on cylinder 3.
A clogged, leaking or faulty injector on cylinder 3.
An air leak at the cylinder 3 intake port.
Mechanical problems, such as a damaged valve or low compression.

How to find the cause

A mechanic usually works like this:

Read all stored codes and freeze frame data.
Remove the cylinder 3 spark plug and inspect it for wear, soot or damage.
Swap the cylinder 3 coil with a working one from another cylinder and read the codes again.
Test the cylinder 3 injector.
If ignition and fuel are fine, run a compression test.

Other ways the code is written

Scan tools and workshop printouts sometimes show the code with extra characters:

P030300

Related codes

Frequently asked questions

Evoca fault code diagnostics is an informational aid and does not replace a professional inspection of your vehicle. Only an inspection of the vehicle at a workshop can confirm the cause of a fault.

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