Problems of the spark plugs: symptoms, cost and affected models
We have documented 8 faults of the spark plugs in 8 engines, affecting 61 models of car in our database. The most important by severity and frequency: spark plug breakage on the 130 hp 1.2 PureTech turbo (1.2 PureTech), oil in the spark plug wells from the rocker cover gasket (BMW N54/N55) and spark plug working loose on the 1.4 i-VTEC engine (1.2 / 1.4 / 1.8 i-VTEC).
How it works and why it fails
Spark plugs
Spark plugs ignite the mixture in petrol engines. They are a maintenance item with a replacement interval, but some engines wear them out early or damage them through coil faults, oil in the combustion chamber or abnormal ignition.
What to do
An engine that shakes, misfires under acceleration or lights the engine warning with codes P0300 to P0304 may have a faulty spark plug or coil. Always use the plug the manufacturer specifies and respect its replacement interval: on direct-injection turbo engines it is shorter.
General explanation by MotorFiable. The specific faults of each engine and car, with their sources, are on the linked pages.
Common symptoms
The symptoms that come up most often in the documented faults of the spark plugs. Open each one to see what other faults cause it.
Problems of the spark plugs by engine
From most to least important (severity × frequency). Each page details the affected versions and years, symptoms, cost and how to check for it.
- 1High severityFrequency: Occasional1.2 PureTechSpark plug breakage on the 130 hp 1.2 PureTech turboOn the 130 hp 1.2 PureTech/e-THP turbo the original spark plugs can break; if a fragment falls into the cylinder it can damage the engine. Autojournal cites a 2015 recall to replace them on the 308 II.
- 2Medium severityFrequency: CommonBMW N54/N55Oil in the spark plug wells from the rocker cover gasketOn the N54 and N55 the rocker cover gasket hardens with age and lets oil seep into the spark plug wells. Guides treat it as a known fault: it smells of burnt oil and can damage spark plugs and coils.
- 3Medium severityFrequency: Occasional1.2 / 1.4 / 1.8 i-VTECSpark plug working loose on the 1.4 i-VTEC engineSeveral 1.4 i-VTEC owners, in both the Civic VIII and the Civic IX, document a spark plug working loose in its seat (in one case it was ejected from the cylinder head while driving); the cases are few, but the same symptom recurs in two different generations.
- 4Medium severityFrequency: OccasionalMitsubishi PHEVSpark plugs and petrol engine software on the Outlander PHEV (campaign R3033111)The DVSA records a recall (R/2017/183) of 14,242 UK Outlanders (PHEV, judging by the defect) built between October 2013 and June 2015: the petrol engine may run poorly and, in the worst case, fail to start in order to charge the traction battery. It is fixed with software and new spark plugs.
- 5Medium severityFrequency: Occasional1.6 THPSpark plugs and ignition coils that wear out early on the 1.6 THPOn the 1.6 THP turbo a noticeable minority of owners replace spark plugs and coils earlier than expected: fiches-auto.fr records ignition warnings in 12% of opinions on the 200 hp THP. It causes judder and the engine warning light.
- 6Low severityFrequency: Occasional1.0 PureTechIgnition coil and spark plug failureOn the 68 hp 1.0 VTi/PureTech, failure of the ignition coils or spark plugs occurs occasionally. It shows up as jerking when accelerating and an engine warning light. It can appear even at low mileage and is fixed without touching the engine.
- 7Low severityFrequency: Occasional1.25/1.4/1.6 Ti-VCTMisfires from coils or spark plugsThere are documented cases of ignition coils replaced several times on the Ford Focus II (1.6 Ti-VCT) and of spark plugs changed at 60,000 km on the Ford Fiesta 1.25, which points to earlier-than-expected ignition system wear on some units.Appears at around 60,000 km
- 8Low severityFrequency: OccasionalMZR gasolinaMisfires from spark plugs and ignition coils in petrol MZR enginesSpark plugs appear among the fault points of the Mazda2 DE in the ADAC statistics cited by gebrauchtwagenberater.de, and fiches-auto.fr attributes the misfires of the Mazda3 1.6 to coils, spark plugs or sensors.
Engines with faults of the spark plugs
Problems of the spark plugs by make
Problems of the spark plugs in your car
7 cars have several documented faults of the spark plugs. Choose yours to see only the ones that affect them, by engine and by year.
Citroën 2
Frequently asked questions
Which engines have the most faults of the spark plugs?
By severity and frequency, the 1.2 PureTech (spark plug breakage on the 130 hp 1.2 PureTech turbo, high severity), the BMW N54/N55 (oil in the spark plug wells from the rocker cover gasket, medium severity), the 1.2 / 1.4 / 1.8 i-VTEC (spark plug working loose on the 1.4 i-VTEC engine, medium severity), the Mitsubishi PHEV (spark plugs and petrol engine software on the Outlander PHEV (campaign R3033111), medium severity), the 1.6 THP (spark plugs and ignition coils that wear out early on the 1.6 THP, medium severity) and the 1.0 PureTech (ignition coil and spark plug failure, low severity). In total we have documented 8 engines with faults of the spark plugs.
What symptoms does a fault of the spark plugs cause?
The most frequently cited in the documented faults: engine fault warning light (check engine), jerking or juddering when accelerating, burning smell, visible oil leak, hard starting or engine will not start and sudden loss of power (limp mode).