Misfire Isolation

1996 Buick Roadmaster BaseSECTION Misfire Isolation
  1. Start engine. Disconnect IAC motor. Using insulated pliers, remove one spark plug wire from a spark plug and ground it against the engine.
  2. Note engine RPM as wire is grounded. Reconnect spark plug wire. Repeat procedure for all cylinders. Stop engine and reconnect IAC motor.
  3. If engine speed dropped equally (within 50 RPM) on all cylinders, see ROUGH, UNSTABLE OR INCORRECT IDLE, STALLING symptom. If there is no engine RPM drop or if there is excessive variation on one or more cylinder, check spark on the respective cylinder(s).
RENDER: 1.0x

NO RELATED

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.