P0300 on a 2018 Honda Cr V

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 Honda Cr V

Ranked from 2,094 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Head gasket failure allowing coolant intrusion into a cylinder
High severity
Repeatedly diagnosed by Honda dealers as the source of random/multi-cylinder misfires on this 1.5L turbo engine; owners report coolant loss, rough running, and misfire codes that resolved (or were attempted to be resolved) with head gasket replacement.
Reported in 12 NHTSA complaints
Parts:head gasket cylinder head
2
Turbocharger failure (oil seal/bearing) allowing oil into the intake/exhaust
High severity
Dealers pointed to a failed turbocharger as the actual root cause in cases where head gasket replacement did not stop smoking/misfire symptoms; oil entering a cylinder fouls combustion and can trigger misfire.
Reported in 3 NHTSA complaints
Parts:turbocharger
3
Fuel injector failure or fouling (often following fuel pump recall work)
Medium severity
Several owners had a specific cylinder misfire (e.g., P0301) traced to a failed/faulty fuel injector, sometimes surfacing after low-pressure fuel pump recall service.
Reported in 2 NHTSA complaints
Parts:fuel injector
4
Worn or fouled spark plugs
Low severity
Standard misfire cause; on this engine plugs can be fouled by coolant/oil intrusion from the head gasket issue above, so replacement alone often does not resolve the misfire.
Common cause
Parts:spark plug
5
Failing ignition coil(s)
Medium severity
A weak or failing coil produces a weak spark on one cylinder; check for a cylinder-specific misfire code and swap coils between cylinders to confirm.
Common cause
Parts:ignition coil
6
Vacuum or intake leak
Low severity
Unmetered air causes a lean misfire, typically worse at idle; check intake boots, PCV lines, and manifold gasket with smoke test.
Common cause
7
Carbon-fouled intake valves
Low severity
Direct-injection engines like this 1.5T lack fuel washing over the intake valves, allowing carbon buildup that disrupts airflow/sealing and can cause misfire over time.
Common cause
8
EGR valve fault
Low severity
A stuck-open EGR valve dilutes the air/fuel charge excessively at idle, producing a rough-running/misfire condition.
Common cause
Parts:EGR valve

Part links go to Amazon search results for this vehicle. As an Amazon Associate, WrenchConnect earns from qualifying purchases — always confirm fitment for your exact trim and engine before ordering.

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.

Matching symptoms

Car Runs Rough Flashing Check Engine Light