Engine Sound Diagnostic Checklist

Vehicle information

• Vehicle year
• Make
• Model
• Engine size
• Engine code (if known)
• Mileage
• Fuel type (gas / diesel / hybrid)
• Transmission type

Customer complaint

• No start
• Hard start
• Rough idle
• Misfire
• Knocking
• Ticking
• Squealing
• Rattle
• Belt noise
• Exhaust noise
• Loss of power
• Stalling
• Other

Engine condition

• Cold engine
• Fully warmed up
• Outside temperature
• Check Engine Light on?
• Stored DTCs (if available)

Recording equipment

• External microphone (preferred)
• Phone microphone
• Wind protection installed
• Phone in Airplane Mode
• Remove phone case if it blocks microphones

Recording environment

• Quiet area
• No radio
• No talking
• Hood open
• Vehicle in Park / Neutral
• Parking brake set

Required audio recordings

Capture each of these separately — short, focused clips beat one long ramble.

• Cold start
  • 20–30 seconds
• Warm idle
  • 30 seconds
• Raise RPM slowly
  • Idle → 2500 RPM
  • Hold 5 seconds
  • Return to idle
• Snap throttle
  • 3 quick throttle snaps
• Hold RPM
  • 1500 RPM
  • 2000 RPM
  • 3000 RPM
  • Hold each for 10 seconds

Recording locations

Capture each test from every viable position — location narrows the source faster than any other input.

• Front of engine
• Driver side
• Passenger side
• Top of engine
• Near accessory belt
• Tailpipe
• Under vehicle (if safe)

Optional advanced tests

• A/C ON
• A/C OFF
• Steering turned fully left / right
• Transmission in Drive (foot on brake)
• Electrical load (headlights, blower, rear defrost)
• Cranking only (no start)
• Power-braking (where safe)

Helpful supporting data

If you have any of these, upload or paste them alongside the audio — they meaningfully raise diagnostic confidence.

• OBD-II live data
• Freeze-frame data
• Fuel trims
• Misfire counters
• Engine RPM
• Coolant temperature
• Intake air temperature
• MAF / MAP readings
• Battery voltage
• Ignition timing
• Relative compression results
• Vacuum readings
• PicoScope waveforms

Maintenance history

• Last oil change
• Oil viscosity used
• Spark plugs replaced?
• Ignition coils replaced?
• Timing belt / chain serviced?
• Recent repairs?
• Accident history?

AI confidence boost

Give the AI multiple reference clips so it can compare relative changes across conditions and locations.

• Cold start
• Hot idle
• Light acceleration
• Heavy acceleration
• Deceleration
• Belt area
• Valve cover
• Intake
• Exhaust
• Alternator
• Water pump
• A/C compressor
• Power steering pump

Final verification

Before you submit, walk this list one more time.

• Recording is clear
• No wind noise
• No voices
• No music
• Entire engine audible
• At least 30-second idle recording
• Multiple engine locations recorded
• OBD-II data attached (if available)

Features that can significantly improve diagnostic accuracy

A wish-list of capabilities that raise confidence when combined with a good recording.

• AI noise reduction to isolate engine sounds.
• Automatic detection of recording location (front, side, tailpipe) using prompts or AI.
• Spectrogram analysis in addition to raw audio.
• Frequency analysis (FFT) to identify knocks, ticks, bearing noise, and belt squeal.
• Automatic engine RPM estimation from audio when OBD-II data isn't available.
• Comparison against a library of known-good recordings for the same engine.
• Combining audio analysis with OBD-II live data, DTCs, and vibration data (from the phone's accelerometer) for a more reliable diagnosis.

Related guides

• Engine sound diagnostics overview
• Knock vs bearing noise
• Belt & timing chain noise