#spark plugs
6 posts in Car Diagnostics blog about "spark plugs" — OBD-II diagnostics, DTC codes, repair. ← All posts
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Spark plugs: when to change them and why "still working" is not an argument
A plug does not fail abruptly — it degrades, and the coil degrades with it. Types, intervals, and why a dearer plug is not always better.
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Ignition coils: the symptoms people mistake for spark plugs
Coils and plugs produce similar symptoms but are tested differently. How swapping separates them, and why coils die in groups.
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Rough when cold, fine when warm: why that happens
A symptom that disappears as the engine warms is a clue, not a triviality. Why a cold start exposes what a warm engine hides.
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Reading spark plugs: what the deposits tell you about the cylinder
A spark plug spends tens of thousands of miles inside a cylinder and brings out a report on everything that happened there. Reading the colours and deposits — and why plugs must be compared against each other.
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P0300: random / multiple misfire — 12 causes and a step-by-step diagnostic algorithm
Deep dive into P0300: why misfires are "random", how to narrow 12 possible causes to one in 30 minutes, what the AI agent reads from Freeze Frame and Live Monitor.
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Engine Misfire at Idle: 10 Causes, DTC Codes and Diagnostic Order
Misfire symptoms explained: why the engine stumbles at idle and under load, how to identify the problem cylinder, which DTC codes to read first.