Suzuki Swift
Small car, simple diagnosis: trims and basic plausibility checks first, then ignition/fuel. Most "mystery" Swifts are air/fuel control or EVAP influence.
Quick triage (5 minutes)
What to capture
- Codes + freeze-frame
- STFT/LTFT at idle and 2,000 rpm
- Misfire counters (if available)
- MAF g/s (or MAP kPa) at idle
- Coolant temp vs intake air temp plausibility
What it usually means
- Lean trims at idle -> intake/PCV leak, purge influence, or MAF bias.
- Random misfire with normal trims -> ignition or mechanical, not mixture.
- Long crank after fuel fill -> EVAP purge/vent behaviour.
- Multiple warning lights at once -> low voltage / ground issue, scan all modules.
Common Swift complaints (honest starting point)
- Hunting/rough idle: check trims, then check purge behaviour (purge valve stuck slightly open can look like an ignition miss).
- Intermittent misfire: confirm which cylinder (if supported) and whether trims are stable. If trims are stable, treat it as ignition first.
- Stumble on tip-in: look for MAF/MAP bias, intake leaks, or throttle body contamination before throwing sensors.
- P0420 after a misfire episode: stabilise misfire/trims first. A catalyst code after repeated misfire is often the consequence, not the root cause.
Usually is / usually isn't
- Usually is: air leaks, purge influence, weak ignition, or basic sensor plausibility.
- Usually isn't: ECU failure, "needs injectors" without evidence, or a catalyst needing replacement before upstream checks.
Typical OBD2 codes you will see
P0171
Lean Bank 1: trims-first plan that stops guessing.
P0300
Random misfire: use counters + mixture logic to narrow it.
P0456
EVAP small leak: fix the basics before parts-darting.
P0420
Catalyst efficiency: upstream faults that masquerade as a bad cat.
Confirmatory tests (quick wins)
- Smoke test intake if trims are lean at idle.
- Temporarily clamp/disable purge (where safe/allowed) if rough idle/lean trims change with purge command.
- Swap-test coils only after you know trims are stable, and verify misfire moves with the coil.
Trust note: Swift faults are usually solvable quickly when you treat them as air/fuel control problems first and prove each step with data.