Symptoms
Mustang Misfire & Rough Idle (2015–2023 S550)
A misfire or rough idle on the S550 Mustang — Coyote 5.0 or 2.3 EcoBoost — should be diagnosed by data, not guesswork. Here's how we trace it to the actual cylinder and cause.
What You’re Noticing
- Rough or shaking idle
- Stumble or hesitation under throttle
- Flashing or steady check-engine light
- Loss of power, occasional backfire
Common Causes
- Coil-on-plug failure — common, often one cylinder
- Worn spark plugs beyond service interval
- Fuel injector fault or clog
- Intake / vacuum leak causing a lean misfire
Whether it's the Coyote 5.0 or the 2.3 EcoBoost, an S550 misfire is best chased with live PCM data — per-cylinder misfire counts and fuel trims — so we fix the real cause and protect your catalytic converters.
Related
Vehicles
Ford MustangGenerations
Mustang S550Systems
Engine PerformanceBook a Service
Ford Engine & Drivability RepairFAQs
Let’s Fix It Right.
Former Ford technician diagnosis in Bridgewater, MA — accurate the first time.