P0300 on Jeep
Random/Multiple Cylinder Misfire Detected
P0300 on Jeep vehicles indicates random/multiple cylinder misfire detected. Au7o has documented this code across 4 Jeep models — most commonly on Grand Cherokee, Grand Wagoneer, Liberty. P0300 means the engine computer detected misfires occurring randomly or across multiple cylinders rather than in one specific cylinder. A misfire is when a cylinder fails to ignite its fuel-air mixture properly, which the computer senses through small fluctuations in crankshaft speed. Because it's not isolated to one cylinder, the cause is usually something that affects the whole engine — like fuel, air, or ignition system problems — rather than a single coil or plug. Persistent or heavy misfiring wastes fuel, runs rough, and can damage the catalytic converter, which is why a flashing check engine light should be taken seriously. Typical repair costs on Jeep range from $100 to $4,500, depending on the specific model and root cause.
Common Causes of P0300
- •Worn or fouled spark plugs (across cylinders)
- •Vacuum or intake air leak
- •Weak fuel pump, clogged fuel filter, or low fuel pressure
- •Failing ignition coils or worn spark plug wires
- •Dirty or faulty mass airflow (MAF) sensor
- •Clogged or dirty fuel injectors
- •Faulty crankshaft/camshaft position sensor
- •Low compression or EGR/PCV system faults
P0300 on Jeep by Model
Jeep Grand Cherokee(1 issue)
- HEMI Engine Tick/Lifter Noise2011-2021
HEMI-equipped Grand Cherokees can develop the characteristic MDS lifter tick. This ticking noise is most noticeable at idle and during light throttle. While often not immediately harmful, it indicates lifter wear from the MDS cylinder deactivation system.
Jeep Grand Wagoneer(1 issue)
- Fuel Injector Leak / Fuel Smell in Engine Bay (3.0L Hurricane)2022-2024
On 3.0L Hurricane twin-turbocharged engines, direct fuel injectors have been reported to develop external fuel leaks at the injector body O-ring seals, allowing raw fuel vapor into the engine bay. The high-pressure direct injection system operates at significantly elevated pressures, and thermal cycling degrades the injector sealing rings prematurely. Owners report a strong fuel odor inside the cabin and in the engine compartment, sometimes accompanied by a visible wet spot or fuel staining on the intake manifold area.
Jeep Liberty(1 issue)
- 3.7L V6 Exhaust Manifold Crack / Valve Cover Oil Leaks2002-2012
The 3.7L PowerTech V6 engine suffers from two common issues: cracked exhaust manifolds (causing ticking noise and exhaust leak) and valve cover gasket oil leaks. The cast iron exhaust manifolds develop stress cracks due to thermal cycling, with the passenger side being more common. TSB 09-001-10 addressed valve cover oil leaks. Head gasket failures have also been reported on higher-mileage engines.
Jeep Wrangler(2 issues)
- 3.6L Pentastar V6 left cylinder head failure / engine tick (early build)2012-2017
Early 3.6L Pentastar V6 Wranglers (especially 2012 and early-2013 builds) suffered a left (driver-side) cylinder head defect where the head would overheat and damage a valve seat/guide, causing low compression, a persistent ticking/tapping noise (often described as a 'left bank tick'), misfires, rough idle and reduced power. FCA acknowledged the defect and issued extended-warranty coverage (campaign X56) extending the head/related coverage to 10 years / 150,000 miles. A separate, related Pentastar tick on later builds is caused by failed rocker-arm needle bearings or collapsed valve lifters rather than the head casting. A class action was filed over the 3.6L tick. Left unaddressed, valvetrain wear can progress to major top-end engine damage.
- Ignition Coil Rail Failure Causing Misfire on 4.0L2000-2006
The 4.0L coil-rail ignition system used on TJ Wranglers is known to develop internal failures that cause intermittent or persistent misfires. Owners report rough idle, hesitation, flashing check-engine lights, and cylinder-specific misfire codes, often after moisture intrusion, age, or heat exposure. Because the rail serves all cylinders, diagnosis can be less straightforward than on engines with individual plug wires.
Looking for P0300 on a different make?
View P0300 across all makes →Frequently Asked Questions
What does P0300 mean on Jeep?▼
P0300 stands for "Random/Multiple Cylinder Misfire Detected." P0300 means the engine computer detected misfires occurring randomly or across multiple cylinders rather than in one specific cylinder. A misfire is when a cylinder fails to ignite its fuel-air mixture properly, which the computer senses through small fluctuations in crankshaft speed. Because it's not isolated to one cylinder, the cause is usually something that affects the whole engine — like fuel, air, or ignition system problems — rather than a single coil or plug. Persistent or heavy misfiring wastes fuel, runs rough, and can damage the catalytic converter, which is why a flashing check engine light should be taken seriously. On Jeep specifically, this code is documented across 4 models.
What causes P0300 on Jeep vehicles?▼
Common causes on Jeep: Worn or fouled spark plugs (across cylinders), Vacuum or intake air leak, Weak fuel pump, clogged fuel filter, or low fuel pressure, Failing ignition coils or worn spark plug wires, Dirty or faulty mass airflow (MAF) sensor. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0300 on a Jeep?▼
Repair costs on Jeep range from $100 to $4,500, depending on the specific model and root cause.
Which Jeep models have P0300 documented?▼
Au7o has documented P0300 on 4 Jeep models: Grand Cherokee, Grand Wagoneer, Liberty, Wrangler.