Cylinder misfire — coil, plug, or valve

Tags: #misfire · #spark-plug · #fuel-consumption

This card collects several distinct root causes found behind cylinder misfires on the X80 — coil-to-cylinder swapping as a cold-weather workaround, a burned exhaust valve causing zero compression, and a coil pack (not the plug) causing a P0301 code in humid weather. Treat these as separate diagnostic patterns, not one single cause¹.

Cylinder 3 winter misfire — resolved (temporarily) by coil swap. One owner's cylinder 3 triggered a check-engine misfire specifically in cold weather, with the fault disappearing entirely once warm season arrived — root cause was never confirmed. As a workaround, the owner swapped the ignition coil from cylinder 1 to cylinder 3 (coil 1→3), which resolved the symptom. This is explicitly stated as a temporary workaround, not a permanent fix — the underlying cause (coil, wiring, or something cold-temperature-related) was not identified¹².

Zero compression in cylinder 1, misfires in cylinders 2-3 — burned exhaust valve. A more serious pattern: zero compression measured in cylinder 1, combined with misfires in cylinders 2 and 3, points to a burned exhaust valve in cylinder 1. This is a serious mechanical problem requiring valve replacement (not just an ignition-side fix). Internal engine inspection — ideally a borescope — is recommended to confirm valve damage before committing to a teardown³⁴⁵.

P0301 (cylinder 1 misfire) in humid weather — coil pack, not the spark plug. When a P0301 code (cylinder 1 misfire) appears periodically and specifically in humid weather, the first suspect should be the coil pack, not the spark plug. In one case the cylinder-1 spark plug showed oil residue/discoloration when pulled, which looked like an obvious culprit, but replacing the plug alone did not resolve the misfire — the coil pack needed replacement. Conflict: the reporting owner (Фаб) initially blamed and replaced the spark plug with the fault persisting; another member (Печной Двор) advised checking the coil pack specifically, which is presented here as the more likely fix for humidity-linked, periodic P0301 faults⁶⁷⁸⁹.

Highway vibration and shift-hunting from budget spark plugs — coils also implicated. A separate case: engine vibration at highway speed and transmission gear-hunting during shifts appeared after installing budget aftermarket spark plugs (Startvolt brand). The problem was resolved by switching to genuine Denso plugs. Some of the vibration/hunting symptoms were separately traced to faulty ignition coils, identifiable by an X mark scratched into the coil casing (a marking convention used by whoever previously diagnosed/swapped it). Diagnostic approach: swap coils between cylinders and see if the symptom follows the coil, or use a multi-pin scanner (X PRO-5) to detect misfires directly — though the X80's OBD-II port may not surface individual per-cylinder misfire codes, limiting how much a basic scanner alone can confirm^1011121314.

Intermittent cylinder-1 misfire without an error code — spark plug suspected (medium confidence). A separate, later owner reports an intermittent ignition misfire error on cylinder 1, with occasional engine stumbling that sometimes throws no error code at all. The community's suggested first suspect is the spark plug condition on cylinder 1, consistent with the spark-plug-side patterns already documented on this card. One other owner reported similar sporadic misfire symptoms, but no confirmed fix is recorded in this batch — confidence: medium¹⁵.

Ignition coil replacement lowered dashboard-reported fuel consumption. After replacing the ignition coil (part sourced via Ozon), one owner's computer-reported fuel consumption decreased by 2.5 liters (per the dashboard trip computer). The community notes the coil is available on Ozon at an economical price. The likely mechanism is that ignition quality (a marginal/failing coil) was affecting combustion efficiency and hence fuel consumption, tying this fuel-economy improvement to the same ignition-coil failure mode already documented above — confidence: medium (single report, dashboard-reported figure, not a controlled fuel test)¹⁶¹⁷¹⁸.

Related pages

• Engine bay pressure washing causes misfire
• Spark plugs — lifespan and wear symptoms
• OEM spark plug specifications
• Cold-start hard cranking — LPG and valve clearance
• Fuel consumption factors and dashboard display

Sources

This page is compiled from 18 community messages. Every fact carries a numbered reference to its original author and message.

Last updated: 2026-09-10