P0300 on a 2020 Acura Rdx

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 2020 Acura Rdx

Ranked from 339 NHTSA owner complaints filed for this vehicle.

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1
Turbocharger/intercooler moisture intrusion causing misfire and limp mode
High severity
A large cluster of owners describe check-engine-light flashing and sudden limp mode during rain/humid weather; several cite dealer diagnoses of moisture entering the turbo/intercooler and Acura Service Bulletin 20-053 (intercooler replacement) or NHTSA recall 23V-858.
Reported in 13 NHTSA complaints
Parts:intercooler
2
Head gasket leak (commonly cylinder 4) allowing coolant/combustion cross-contamination
High severity
Two owners had dealer-diagnosed head gasket leaks (one specifically at cylinder 4) causing engine judder and repeat misfire-like symptoms after initial repair.
Reported in 2 NHTSA complaints
Parts:head gasket
3
Worn spark plugs
Medium severity
Standard high-mileage misfire cause; inspect gap and electrode wear, especially on cylinders showing the misfire counts.
Common cause
Parts:spark plugs
4
Ignition coil failure
Medium severity
A weak or dying coil-on-plug unit causes a repeatable misfire on one cylinder; swap coils cylinder-to-cylinder to confirm.
Common cause
Parts:ignition coil
5
Carbon-fouled intake valves
Medium severity
Direct-injection engines like this 2.0L turbo don't get fuel washing the backs of the intake valves, letting carbon buildup disrupt airflow/mixture and cause misfires over time.
Common cause
6
Clogged or leaking fuel injector
Low severity
An injector delivering too little (or dribbling) fuel to one cylinder produces a persistent misfire on that cylinder.
Common cause
Parts:fuel injector
7
Vacuum or intake air leak
Low severity
Unmetered air entering after the throttle body upsets the air/fuel ratio enough to cause a misfire under certain conditions.
Common cause
8
EGR valve fault (stuck open)
Low severity
Excess exhaust gas recirculated at the wrong time can dilute the intake charge enough to cause a misfire, especially at idle/light load.
Common cause

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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.

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Matching symptoms

Car Runs Rough Flashing Check Engine Light