P0308: Cylinder 8 Misfire Detected

What P0308 usually means

P0308 means cylinder 8 is the primary misfire cylinder. Like P0307, it often shows up on V8 layouts where rear-bank access, heat exposure, and plug-well contamination complicate diagnosis. The code still follows the same rule: prove spark, fuel, air, and compression in that order instead of guessing from the cylinder number.

Start here before chasing parts

• Scan first: save freeze-frame and pending codes before clearing anything.
• Confirm the complaint: compare the stored code with current drivability symptoms.
• Use context: trims, live data, and related codes usually narrow the fault faster than guesswork.
• Work simplest to hardest: leaks, connectors, maintenance items, and known patterns before expensive components.

Suggested workflow

1. Inspect the cylinder 8 plug, coil, and connector condition.
2. Swap suspect ignition parts if practical and see whether the misfire moves to another cylinder.
3. Test injector command and contribution before condemning the injector itself.
4. Perform compression or leak-down testing if electrical and fuel checks come back inconclusive.
5. Verify the repair under real driving load and confirm the misfire counter stays flat.

Common mistakes

• Diagnosing cylinder 8 from memory without confirming engine-specific numbering.
• Replacing plugs and coils but ignoring the fluid leak that contaminated them.
• Assuming the catalyst is fine after a long active misfire just because the engine runs better now.

Practical fix guidance

• Correct the root cause on cylinder 8 and clean up any leak or routing issue that would damage new parts again.
• If the misfire was severe, monitor for later catalyst efficiency complaints because the converter may have been stressed.
• Finish with a complete road test so the code is cleared by proof, not just by erasing memory.

Affected brands in this MVP

• Ford
• Chevrolet

Brand hubs help broaden internal linking now and can evolve into make-specific diagnostic notes later.