P0300 on a 2011 Toyota Camry
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 2011 Toyota Camry
Ranked from 620 NHTSA owner complaints filed for this vehicle.
- 1
Worn piston rings / excessive oil consumption fouling spark plugs (2AZ-FE/2AR-FE design defect)
High severityA very large share of the complaints describe the well-documented Camry oil-ring defect (burning a quart of oil every few hundred to ~2,000 miles); the resulting oil in the combustion chamber fouls spark plugs and lowers effective compression, both direct contributors to a random misfire.
Reported in 14 NHTSA complaints - 2
Timing chain / VVT gear damage
High severityOne owner's valve cover fractured and damaged the VVT gears and timing chain, throwing valve timing off enough to make the engine shake and run rough while driving.
Reported in 1 NHTSA complaint - 3
Worn spark plugs
Low severityStandard high-mileage wear item; a widening gap or fouled tip is one of the most common misfire causes on any engine.
Common causeParts:spark plugs - 4
Failing ignition coils
Medium severityCracked or internally shorted coils drop spark energy to one cylinder; swapping coils between cylinders and watching the misfire follow confirms this.
Common causeParts:ignition coil - 5
Clogged or leaking fuel injectors
Medium severityA partially blocked or dribbling injector under- or over-fuels a cylinder, producing an isolated or random misfire.
Common causeParts:fuel injector - 6
Vacuum leaks
Low severityA cracked intake hose or brittle gasket lets in unmetered air, leaning out one or more cylinders enough to misfire, especially at idle.
Common cause - 7
Carbon-fouled intake valves
Low severityCarbon deposits on the valves disrupt airflow and atomization on affected cylinders, a common contributor as these engines accumulate miles.
Common cause - 8
EGR valve fault
Low severityA stuck-open EGR valve over-dilutes the intake charge at idle/light load, causing a lean misfire on one or more cylinders.
Common causeParts:EGR valve
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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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