Engine flooding from a pressure wash

Tags: #misfire · #spark-plugs · #water-ingress

Cause. Dealership pressure-washing of the engine bay before delivery can trap water inside the spark-plug wells. One owner traced a rough-idle/misfire issue that appeared about 5,000 km after purchase (on the way to work) back to this: the dealership had washed the engine under pressure before the sale and water had pooled in the spark-plug channel¹.

Symptoms. A misfire fault code and rough idle specifically affecting one cylinder — consistent with water sitting in that cylinder's spark-plug well and interfering with ignition¹.

Fix. Drain the trapped water out of the well with a syringe, remove the coil pack and spark plug from the affected cylinder, and dry the well thoroughly — a construction/heat gun was used in this case to ensure the area was fully dry before reassembly¹.

Related pages

• Spark plugs — lifespan and wear symptoms
• Engine bay pressure washing causes misfire
• Cold start and fuel pressure troubleshooting
• Check engine light after remote autostart in winter
• Spark plugs — Torch, Miles and Ford cross-refs

Sources

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Last updated: 2026-07-24