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Audi P0304

Audi P0304 Code

Audi P0304 still means cylinder 4 is misfiring, but the high-value split is between a true cylinder-4 ignition or injector fault and the wider airflow, fuel, timing, or mechanical problems that keep making that cylinder fail first.

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Quick answer

AI-CITATION READY

What it means

The repo-backed Audi matrix for P0304 follows the same broader misfire tree as the existing Audi cluster: worn spark plugs or coils, incorrect ignition timing, vacuum leaks, weak fuel pressure, EGR or MAF faults, crank or cam sensor issues, throttle-position faults, and deeper mechanical problems all remain possible. The useful Audi page should start with cylinder 4 because the code is specific, but it should not collapse the diagnosis into a guaranteed plug-or-coil story when mixture, timing, or compression faults can keep targeting that cylinder.

Can you drive with it?

With caution. You can drive short distances at low speeds, but prolonged driving risks catalytic converter damage and increased emissions.

Most common causes

  • Start with cylinder-4-specific ignition and injector checks, because a worn plug, weak coil, or injector fault is still the fastest fix when the misfire counter stays pinned to one hole.
  • If P0304 returns after basic swaps, vacuum leaks, weak fuel pressure, or MAF bias can still load cylinder 4 first instead of proving the replacement ignition part was wrong.
  • When misfire counters begin spreading or scan data shows timing correlation issues, crank or cam signal faults, or mechanical compression problems, the Audi branch is wider than repeatedly replacing coils.

Typical repair cost

Start with the generic P0304 repair path, then narrow the decision using Audi-specific checks before replacing major parts.

Indexation guardrail

This page is published as a guarded manufacturer supplement. It canonicalizes back to the generic parent and stays out of the sitemap until the repo has both a matching manufacturer_codes row and approved indexation evidence for this exact pair within the active release lane.

01 / What changes here

The repo-backed Audi matrix for P0304 follows the same broader misfire tree as the existing Audi cluster: worn spark plugs or coils, incorrect ignition timing, vacuum leaks, weak fuel pressure, EGR or MAF faults, crank or cam sensor issues, throttle-position faults, and deeper mechanical problems all remain possible. The useful Audi page should start with cylinder 4 because the code is specific, but it should not collapse the diagnosis into a guaranteed plug-or-coil story when mixture, timing, or compression faults can keep targeting that cylinder.

02 / Matrix evidence

Worn out spark plugs, ignition wires, coil(s), distributor cap and rotor (when applicable), Incorrect ignition timing, Vacuum leak(s), Low or weak fuel pressure, Improperly functioning EGR system, Defective Mass Air Flow Sensor, Defective Crankshaft and or Camshaft Sensor, Defective Throttle Position Sensor, Mechanical engine problems (i.e.—low compression, leaking head gasket(s), or valve problems)

03 / Brand patterns

  • Start with cylinder-4-specific ignition and injector checks, because a worn plug, weak coil, or injector fault is still the fastest fix when the misfire counter stays pinned to one hole.
  • If P0304 returns after basic swaps, vacuum leaks, weak fuel pressure, or MAF bias can still load cylinder 4 first instead of proving the replacement ignition part was wrong.
  • When misfire counters begin spreading or scan data shows timing correlation issues, crank or cam signal faults, or mechanical compression problems, the Audi branch is wider than repeatedly replacing coils.

04 / Diagnostic starting points

  1. Confirm whether the misfire counter stays isolated on cylinder 4 or starts moving to other cylinders before you call it a simple plug or coil job.
  2. Inspect and, if possible, swap the cylinder-4 spark plug and coil first, then verify injector operation, connector condition, and any obvious intake leak near that runner.
  3. If the misfire returns under load or after ignition swaps, verify fuel pressure, MAF behavior, and related cam-crank or throttle faults before blaming the catalyst or control module.
  4. Move to compression, leak-down, and timing-correlation checks if the cylinder-4 hardware looks good and P0304 keeps coming back.

05 / Vehicle-family notes

These are on-page notes only. No standalone model/year/engine pages are published or indexed from this wave.

Audi A4

  • A4 searches often need a clean split between a cylinder-4 ignition fault and the airflow, fuel, or timing problems that keep that cylinder misfiring first.
  • Use misfire counters, fuel-trim context, and any cam-crank correlation clues before treating the code like a guaranteed coil-only repair.

Audi Q5

  • Q5 demand often centers on whether cylinder 4 truly owns the fault or whether mixture, fuel-pressure, or timing problems are loading that cylinder first.
  • If the engine shakes hard or the light flashes, protect the catalyst first and finish the ignition-versus-system split before normal driving.

06 / When exact fitment matters

Audi cylinder numbering, coil-pack layouts, intake routing, and timing-system failure patterns vary by engine family and calibration. Verify the exact engine before assuming where cylinder 4 sits or condemning coils, injectors, timing hardware, or compression components from pattern evidence alone.

07 / Baseline parent page

Use the generic parent page for the full code definition, symptoms, repair table, and FAQ:

Open P0304 parent page

08 / Source notes

  • Generic OBD2.help P0304 content for the base cylinder-4 misfire definition, risk, and repair order.
  • Repo-backed matrix evidence is present via the AUDI manufacturer_codes row for P0304: worn spark plugs or ignition coils, incorrect ignition timing, vacuum leaks, weak fuel pressure, EGR or MAF faults, crank or cam sensor faults, throttle-position issues, and mechanical engine problems.

09 / Source and method

DATA BASIS
OBD-II REFERENCE + OBD2.HELP
METHOD
STATIC VALIDATION
SAFETY
INFORMATIONAL

This page combines OBD-II diagnostic reference data with OBD2.help generated diagnostic guidance for code meaning, likely causes, and repair direction.

Publishing uses deterministic schema and build validation, plus manual spot checks on representative pages before release.

Safety-critical diagnosis and repairs should be confirmed with a qualified mechanic, especially when the vehicle is misfiring, overheating, or losing power.