Common Symptoms
- Check engine light illuminated
- Rough idle or engine vibration
- Loss of power or hesitation during acceleration
- Poor fuel economy
- Engine stumbling or surging
- Flashing check engine light under load
Most Likely Root Causes
- Faulty ignition coil on cylinder 4
- Worn or fouled spark plug in cylinder 4
- Fuel injector failure or clogging on cylinder 4
- Low compression in cylinder 4
- Vacuum leak affecting cylinder 4
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Component Location
Cylinder 4 is typically located on the driver side bank of V-configuration engines or varies by firing order on inline engines.
Manufacturer Notes
Some manufacturers recommend swapping ignition coils or fuel injectors between cylinders to confirm component failure before replacement.
Also diagnosing J1939 SPN/FMI codes?
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