CdMec
Sign in

DTC code

P0300

Random/Multiple Cylinder Misfire Detected

Technical guide

Symptoms

  • Rough idle
  • shaking
  • loss of power
  • check engine light (may flash)
  • excessive fuel consumption
  • catalyst damage risk if persistent

Probable causes

  • Random/multiple cylinder misfire
  • worn spark plugs (most common)
  • faulty ignition coil(s)
  • clogged fuel injectors
  • vacuum leak
  • low compression
  • low fuel pressure
  • camshaft timing issue

Diagnostic steps

  1. Replace spark plugs if at or past service interval.
  2. Test ignition coils by swapping between cylinders.
  3. Perform compression test - all cylinders within 10%.
  4. Check for vacuum/intake leaks.
  5. Test fuel pressure.
  6. Check injector operation.
Brand-specific notes (Ford, Nissan, VW/Audi/Skoda/Seat)

Ford · Focus/Fiesta/Mondeo · all petrol engines

Symptoms

  • Rough idle
  • shaking
  • loss of power
  • check engine light (may flash indicating catalyst damage risk)
  • excessive fuel consumption

Probable causes

  • Worn spark plugs (most common)
  • faulty ignition coil
  • clogged fuel injectors
  • carbon buildup on intake valves (EcoBoost engines)
  • low compression
  • vacuum leak

Diagnostic steps

  1. Replace spark plugs if over service interval.
  2. Swap ignition coils between cylinders to identify faulty one.
  3. Perform compression test.
  4. Check for vacuum/intake leaks with smoke test.
  5. On EcoBoost: walnut blast intake valves if high mileage.

Nissan · Micra/Note/Qashqai/Juke/X-Trail · HR12/HR16/MR18/MR20/R9M all engines

Symptoms

  • Rough idle
  • shaking
  • loss of power
  • check engine light
  • excessive fuel consumption

Probable causes

  • Worn spark plugs (Nissan HR engines particularly sensitive)
  • failed COP ignition coil
  • clogged fuel injectors
  • vacuum leak at intake manifold
  • low fuel pressure
  • on 1.5 dCi (K9K): faulty glow plugs causing misfire on cold start

Diagnostic steps

  1. Replace spark plugs - use only specified NGK/Denso plugs for Nissan.
  2. Test ignition coils by swapping.
  3. Check for intake air leaks.
  4. On diesel K9K: check glow plugs.
  5. Clean or replace fuel injectors.
  6. Compression test if above fails.

VW/Audi/Skoda/Seat · 16684 · all engines

Symptoms

  • Rough idle
  • shaking
  • loss of power
  • check engine light flashing
  • excessive fuel consumption

Probable causes

  • Faulty ignition coils (very common on 1.8T/2.0T)
  • worn spark plugs
  • bad fuel injectors
  • low compression
  • intake air leak
  • camshaft timing issue

Diagnostic steps

  1. Check and replace spark plugs if worn.
  2. Test ignition coils - swap to identify faulty coil.
  3. Perform compression test.
  4. Check for vacuum/intake leaks.
  5. Check fuel pressure and injector operation.

Cross-checked technical synthesis (QA). It does not replace the manufacturer's procedure.

Models most reported with this code (NHTSA)

Ford Escape 34Ford Fusion 18Kia Soul 12Honda Accord 11Ford F-150 10Honda CR-V 9Mitsubishi Lancer Evolution 7Ford Edge 7

Count of distinct owner complaints mentioning the code. US data — same engines, same failures.

AI here is a librarian: this page shows only what mechanics confirmed, or says “unknown”. It never suggests a diagnosis — MECCANIC interprets the code, never your car.

0 confirmed cases on P0300

Nothing confirmed yet for this code. No guess is offered on purpose.

Open a case
P0300 — Random/Multiple Cylinder Misfire Detected — CodMec