P0316: Engine Misfire Detected on Startup (First 1000 Revolutions)

What it means

The misfire monitor detected misfires during the first 1000 revolutions after startup but the engine then settled. Often caused by fouled spark plugs that warm up clean, weak ignition coils, or a borderline cold-start fuel mixture.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The misfire monitor checks crankshaft speed shortly after the engine starts, when cold-start combustion can be less stable. P0316 is set when the monitor detects misfires during the first 1,000 crankshaft revolutions after startup, even if the engine runs more smoothly once it warms up.

Common causes

Most likely first.

1. Spark plugs fouled when cold
2. Ignition coil weak below operating temperature
3. Cold-start mixture too lean (fuel pressure, leaking injectors at rest)

Symptoms

• Check engine light on or flashing
• Rough idle and uneven running
• Power loss, hesitation under acceleration
• Increased fuel consumption
• Possible smell of unburned fuel from exhaust

How to diagnose it

1. Read freeze-frame data and misfire counts from a cold start, noting how long the engine had been off and the temperature when the fault occurred.
2. Inspect spark plugs and ignition coils for fouling, wear, moisture, or damage that could cause a cold-only misfire.
3. If coils are interchangeable, swap a suspect coil and check whether the cold-start misfire follows it on a later cold start.
4. Check for signs of fuel leakage or injector seepage after shutdown and review fuel-trim data during cold startup.
5. If ignition and injector checks do not identify the cause, test fuel pressure and cylinder compression according to the manufacturer’s service information.

Common fixes

• Replace fouled or worn spark plugs identified during inspection.
• Repair an ignition coil or connector fault that causes the cold-start misfire.
• Clean or replace a leaking or restricted injector if testing confirms the fault.
• Repair a fuel-pressure problem if measurements are outside the manufacturer’s specification.
• Address low compression if mechanical testing identifies it.

Can I keep driving?

If the check engine light flashes during startup, avoid continued driving until the misfire stops; unburned fuel can damage the catalytic converter. A steady light with brief, mild roughness calls for prompt diagnosis, especially if cold-start misfires are becoming more frequent.