P0300 on a 2018 Chrysler Pacifica
P0300 is a generic OBD2 powertrain code for random or multiple cylinder misfire. Unlike P0301 through P0308, it does not point to one specific cylinder, so the cause can be ignition, fuel, air, sensor, or mechanical.
Not your vehicle? See general P0300 info.
Most common causes on the 2018 Chrysler Pacifica
Ranked from 823 NHTSA owner complaints filed for this vehicle.
- 1
Blown Head Gasket / Coolant Intrusion
High severityCoolant leaks into the cylinders (often cylinder 3 or 5), causing misfires, rough idle, overheating, and white smoke from the exhaust. Confirmed by borescope inspection or cylinder leak-down test.
Reported in 13 NHTSA complaints - 2
Warped or Defective Cylinder Head
High severityManufacturing defects or overheating can cause the cylinder head to warp, leading to coolant intrusion and misfires. Confirmed by removing the cylinder head and checking for warpage or internal damage.
Reported in 4 NHTSA complaints - 3
Faulty Spark Plugs or Ignition Coils
Medium severityWorn or damaged spark plugs and ignition coils fail to ignite the air/fuel mixture properly, causing misfires. Confirmed by inspecting the plugs/coils and checking for wear, damage, or coolant fouling.
Common cause - 4
Vacuum Leaks
Medium severityUnmetered air entering the intake manifold leans out the air/fuel mixture, leading to random misfires. Confirmed by smoke testing the intake system or listening for hissing noises.
Common cause - 5
Fuel Delivery Issues (e.g., Injectors, Fuel Pump)
Medium severityClogged fuel injectors or low fuel pressure prevent the correct amount of fuel from reaching the cylinders, causing a lean misfire. Confirmed by checking fuel pressure and injector pulse/flow.
Common cause - 6
Engine Timing Issues
High severityA stretched timing chain or faulty variable valve timing (VVT) components can throw off engine timing, resulting in multiple cylinder misfires. Confirmed by checking timing marks and VVT solenoid operation.
Common cause
These causes are aggregated from NHTSA owner complaints and general repair knowledge — this is not a diagnosis. P0300 on your car still needs shop confirmation before any repair.
Common symptoms
- Flashing or steady check engine light
- Rough idle
- Shaking under acceleration
- Loss of power
- Fuel smell from exhaust
What to check before replacing parts
Scan for cylinder-specific misfire codes
Look for: A companion P0301–P0308 pins the misfire to one cylinder — start there. P0300 with no cylinder code points at something hitting several at once: fuel pressure, a large vacuum leak, or timing.
Inspect the spark plugs and coils
Look for: Pull the plugs: black/sooty = rich, oily = oil intrusion, white/blistered = lean or overheating, cracked porcelain or an out-of-spec gap = replace. Then swap a coil to another cylinder — if a cylinder-specific code follows the coil, the coil is bad.
Check fuel trims for a vacuum leak
Look for: High positive short- and long-term trims (worst at idle, improving as RPM rises) mean unmetered air is getting in. Smoke-test the intake and listen for hissing.
Verify fuel pressure
Look for: Compare running/cranking pressure to the vehicle spec. Low or dropping pressure starves multiple cylinders and reads as a random misfire — suspect the pump, filter, or regulator.
Compression / leak-down test if ignition and fuel check out
Look for: A cylinder 15%+ below the others, or leak-down hissing from the intake (intake valve), exhaust (exhaust valve), or oil filler (rings), means the misfire is mechanical — not a swap-in part.
Rather have a pro handle it? Find a vetted local mechanic.