A cylinder can miss its expected power stroke while its piston keeps moving. Follow cylinder four through normal combustion and a missing push, then see how the engine computer detects uneven crankshaft rotation.
P0304 identifies a detected misfire at cylinder four; it does not identify the failed part. Ignition, fuel or mixture, and compression problems can lead to a similar missing contribution.
This original 3D explanation uses the 2013 Mitsubishi Outlander III GF7W 2.0L 4J11 as its research example, with same-generation 4J1 service-manual references. The cutaway, timing, combustion graphics, cylinder numbering direction and signal bars are teaching simplifications, not OEM CAD, a measured vehicle waveform or repair-location instructions. The illustration shows a clear near-zero-power case; real misfires can still have partial combustion.
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Video Summary
AI Generated
This video explains how an engine's computer detects a cylinder misfire. While an engine continues to run even if one cylinder fails to produce power, the resulting inconsistency in crankshaft speed allows the onboard computer to identify which specific cylinder is underperforming, though further mechanical testing is required to find the actual cause.
An engine can keep turning even when one cylinder misses a power stroke.
So why does the whole car stumble? And how can its computer tell which cylinder was weak?
Here's a simplified cutaway of a four-cylinder gasoline engine.
All four pistons share one crankshaft. Each cylinder takes in air, compresses it,
makes a power stroke, and clears its exhaust over two crankshaft turns.
Their power strokes arrive one after another. One, three, four, two.
Watch the orange push from each cylinder reach the same shaft.
Now follow cylinder four. Its intake valve opens,
air enters, and an injector sprays fuel into the intake port.
The piston rises and compresses the mixture. A spark begins combustion.
Expanding gas pushes the piston down. Its connecting rod turns the crankshaft.
That is a normal power stroke. The orange glow and arrow show the push.
They are teaching graphics, not a camera view inside a running engine.
Replay that same moment. The crank reaches the same position,
but cylinder four gives almost no push. Notice the missing orange arrow. Its piston
still travels downward because the other three cylinders and the spinning crankshaft carry it
through. A misfire means this cylinder's expected contribution is absent or too weak.
It does not mean the piston has stopped, and this illustration does not claim that
every real misfire has no flame at all. Compare the two rotations.
With four normal power strokes, the shaft gains speed in a repeating pattern.
When cylinder four misses, it gains less speed after that expected event.
The change can be small, but if it repeats, the engine can shake or feel rough.
A single rough moment is not enough to diagnose a particular fault.
The crankshaft position sensor tracks rotation. The engine computer uses the timing of that
signal to assess changes in crankshaft speed and angular acceleration.
It does not see the combustion itself. When the pattern meets its diagnostic conditions,
it can flag a cylinder-specific misfire. P0304 means misfire detected at cylinder four.
It identifies where the weak contribution was detected, not which part failed.
The signal bars here are simplified, not a measured waveform from this vehicle.
Several faults could produce that same missing push. The spark could be weak or absent. The
air-fuel mixture might be wrong. The cylinder might also lose compression,
so it cannot build normal pressure. Those are different paths to a similar result.
Testing the ignition, fueling, and mechanical condition is how a technician separates them.
So the computer reads the uneven turning of the crankshaft and points to the weak cylinder.
The cause is a second question. A misfire code starts the diagnosis. It does not finish it.
