{
  "title": "The Cold Misfire Field Guide",
  "author": "Armando Torres",
  "author_site": "https://armando-torres.4ort.net",
  "description": "Diagnostic method for a cold engine misfire — symptom to circuit to part.",
  "updated": "2026-08-20",
  "first_move": {
    "ask_before_opening_hood": [
      { "question": "Does it miss at idle, under load, or both?", "narrows": "idle-only => low-speed circuit; load-only => fuel supply or ignition under RPM; both => whole cylinder or bank" },
      { "question": "Cold, hot, or always?", "narrows": "cold-only => worn gap / sensor-open-warm; hot-only => heat soak of coil or crank sensor; always => compression or fixed fuel problem" },
      { "question": "Code? which bank/cylinders?", "narrows": "misfire code narrows cylinders; lean/rich points at fuel trim" }
    ]
  },
  "circuits": {
    "ignition": ["spark plug gap + carbon tracking", "plug wire resistance", "distributor cap + rotor (crack/carbon track)", "coil", "crank position sensor"],
    "fuel": ["fuel pressure at rail", "injector pulse", "dirty/leaky injector", "fuel filter", "pump"],
    "compression": ["compression test all cylinders", "leak-down test if uneven", "valve lash", "head gasket"]
  },
  "diagnostic_order": [
    "Read code, then verify via live-data cylinder balance test",
    "Fuel pressure at rail: key-on, then under idle",
    "Inspect plugs: color, gap, carbon track; wire resistance; cap+rotor inside and out",
    "Compression test if miss follows a single cylinder in all conditions",
    "Name and price a part only after 1-4"
  ],
  "failure_mode_highlight": {
    "name": "cracked distributor cap",
    "behavior": "carbon track between towers arcs to wrong plug when cold; carbon track heats and resistance suppresses the errant arc as engine warms; miss fades by warm-up",
    "test_note": "if you only test the car warm you will never catch it",
    "season": "high humidity (e.g. Texas August)"
  },
  "safety": "Never pull a plug wire off a running/hot engine to listen for a miss — coil can exceed 20000V. Kill the engine, ground the plug, crank, or use a power probe/timing light."
}