Cylinder 1 Misfire

Swap the ignition coil with another cylinder and see if the code follows

Look for: If the misfire follows the coil to its new cylinder, the coil is bad. If cylinder 1 keeps misfiring with a known-good coil installed, the fault is in that cylinder's plug, injector, wiring, or mechanical condition.

Inspect the cylinder 1 spark plug

Look for: Black/sooty deposits point to a rich mixture, oily deposits point to oil intrusion past the rings or valve seals, and a white/blistered or cracked plug points to a lean or overheating condition. A worn or out-of-spec gap alone can cause a misfire under load.

Check cylinder 1 injector pulse and flow

Look for: A dead injector shows no pulse at all (noid light or clicking test) or measurably lower flow/resistance than the other injectors — either confirms a fuel-delivery cause rather than ignition.

Look for an intake leak near cylinder 1

Look for: Hissing at idle or a smoke-test leak right by that runner or intake gasket lets in unmetered air, leaning out just that cylinder enough to misfire.

Test compression on cylinder 1

Look for: Compression well below the other cylinders (or below spec) means the misfire is mechanical — a valve, ring, or head gasket problem that no ignition or fuel part will fix.