Fiat 500X Spark Plugs: Intervals, Fitment & Warning Signs
On the 500X, if TwinAir, even after replacing a faulty coil the ECU can genuinely stay stuck in a reduced-power mode until fault memory is properly cleared.
Illustration for editorial purposes
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OEM Part Number: confirm via engine code — aftermarket NGK 90418 / Bosch 0 242 135 563
| Petrol engines in this generation | 1.0 (334.AXN1B) 114 and 120 HP; 1.3 (334.AXR11) 150 HP; 1.3 179 HP; 1.4 (334AXC1B) 136-162 HP; 1.4 4x4 (334AXF22) 163 and 170 HP; 1.6 (334AXE1A) 110 HP; 2.4 182-188 HP; 1.4 LPG (334AXL1B) |
|---|---|
| Spark plugs (aftermarket) | NGK 90418 (iridium, M12x1.25, 14 mm, thread 26.5 mm); NGK 93311 (iridium, 16 mm, thread 19 mm); NGK 95536 (iridium, gap 1.0 mm, 16 mm); NGK 4983 and 94037 (nickel, 16 mm); Bosch 0 242 135 563 (gap 0.8 mm, 16 mm, 23 Nm); Bosch 0 242 140 514 (gap 0.7 mm, 16 mm); Bosch 0 242 235 665 (gap 0.8 mm, M14x1.25); Denso IXU27 (iridium, 16 mm, 17 Nm) |
| Genuine (OE) numbers quoted | Denso IXU27 = 55210685; Denso IXU01-27 = J4520IXU0127; Denso XU22TT = 1WT418110; Mopar 46344793, 55259565, 46344792 (OE parts) |
| Fitment notes | Most plugs are M12x1.25 with 16 mm hex; the M14x1.25 plugs (Bosch 0 242 235 665, Ridex 686S0052, Champion OE038/T10) are listed for the larger engines. Plugs are not tied to engines and no change interval is shown. |
A Genuinely Important Technical Fact Worth Knowing on TwinAir Models — Fiat 500X Spark Plugs
If you've replaced a faulty ignition coil on the TwinAir engine but the car still feels down on power, this is genuinely worth knowing: when a coil fails, the ECU logs misfire faults and can drop into a catalyst-protection limp mode. Even after the coil has been correctly replaced, the ECU can remain in this reduced-power state until the fault memory has been properly cleared using the correct diagnostic equipment — cheap, generic OBD readers often can't display or clear these specific fault codes.
It's also genuinely worth knowing a useful UK consumer rights point: a persistent, unresolved misfire that a dealer fails to properly diagnose after multiple attempts, particularly on a recently purchased car, can potentially be sufficient grounds for rejecting the car entirely under UK consumer protection law.
Fiat 500X Spark Plugs: A Cheap Part That Causes Expensive-Feeling Problems
On the Fiat 500X, spark plug wear tends to creep in quietly — idle gets a little rougher, throttle response softens slightly — the kind of symptoms that get blamed on almost anything else under the bonnet. Given how cheap the part itself is, it's an easy one to put off for longer than makes sense.
Fiat 500X Spark Plugs: Watch: Replacing It
Names 500X; 2.4 version at https://www.youtube.com/watch?v=WMqj_RbgjPs
Fiat 500X Spark Plugs: What They Do
Inside each cylinder of the Fiat 500X, spark plugs ignite the compressed fuel-air mixture, and their condition has a direct effect on combustion efficiency, fuel economy and how smoothly the engine runs. Petrol engines can't function without them; diesels don't use spark plugs, relying on compression alone to ignite fuel.
Fiat 500X Spark Plugs: Generations & Spark Plug Count
| Diesel variants | Not applicable — diesel engines use compression ignition and have no spark plugs at all |
|---|---|
| Petrol variants (all trims) | 4 spark plugs — one per cylinder |
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Fiat 500X Spark Plugs: Warning Signs, DIY Difficulty & Aftermarket Advice
These are the same regardless of make or model — see our full Spark Plugs Guide for symptoms of worn plugs, why matching your exact plug specification matters, and trusted brands to buy from.
More Fiat Spark Plugs
The same part, covered across other Fiat models.