P0308 on Jeep
Cylinder 8 Misfire Detected
P0308 on Jeep vehicles indicates cylinder 8 misfire detected. Au7o has documented this code across 2 Jeep models — most commonly on Commander, Grand Cherokee. P0308 means the engine computer detected a misfire on cylinder number 8 — that cylinder is failing to combust properly or at the correct time. The PCM identifies it by monitoring crankshaft speed variations as cylinder 8 fires. Misfires waste fuel, increase emissions, and can overheat and damage the catalytic converter, so a hard misfire may cause a flashing check engine light. Typical symptoms include rough idle, vibration, hesitation, and reduced power. Typical repair costs on Jeep range from $2,200 to $7,500, depending on the specific model and root cause.
Common Causes of P0308
- •Worn, fouled, or incorrectly gapped spark plug on cylinder 8
- •Failed ignition coil or coil-on-plug for cylinder 8
- •Faulty, clogged, or leaking fuel injector
- •Vacuum or intake air leak affecting that cylinder
- •Low compression (worn rings, burnt/leaking valve, head gasket)
- •Damaged spark plug wire or boot (on applicable engines)
- •Carbon buildup or sticking valve
P0308 on Jeep by Model
Jeep Commander(1 issue)
- 4.7L PowerTech V8 Dropped Valve Seat / Cracked Cylinder Head Causing Sudden Single-Cylinder Misfire2006-2009
The 4.7L SOHC PowerTech V8 (2006-2009 Commander) presses hard steel valve seats into aluminum cylinder heads. Any overheat event - and the XK's cooling system is itself a weak point - lets the aluminum head grow away from the seat, loosening it. The seat then drops into the combustion chamber, or the head cracks between the valve seats. The failure is usually sudden: a healthy-running engine develops a violent single-cylinder misfire, a hammering noise and total loss of compression in that hole within minutes. Commander owners report it most often on the 4.7 after a cooling-system incident, and Chrysler's 2005-2007 4.7 heads are the ones most cited. Compression on the dead cylinder reads near zero; a borescope shows the seat lying on the piston crown or a valve pocket that has been pounded out.
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.
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View P0308 across all makes →Frequently Asked Questions
What does P0308 mean on Jeep?▼
P0308 stands for "Cylinder 8 Misfire Detected." P0308 means the engine computer detected a misfire on cylinder number 8 — that cylinder is failing to combust properly or at the correct time. The PCM identifies it by monitoring crankshaft speed variations as cylinder 8 fires. Misfires waste fuel, increase emissions, and can overheat and damage the catalytic converter, so a hard misfire may cause a flashing check engine light. Typical symptoms include rough idle, vibration, hesitation, and reduced power. On Jeep specifically, this code is documented across 2 models.
What causes P0308 on Jeep vehicles?▼
Common causes on Jeep: Worn, fouled, or incorrectly gapped spark plug on cylinder 8, Failed ignition coil or coil-on-plug for cylinder 8, Faulty, clogged, or leaking fuel injector, Vacuum or intake air leak affecting that cylinder, Low compression (worn rings, burnt/leaking valve, head gasket). Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0308 on a Jeep?▼
Repair costs on Jeep range from $2,200 to $7,500, depending on the specific model and root cause.
Which Jeep models have P0308 documented?▼
Au7o has documented P0308 on 2 Jeep models: Commander, Grand Cherokee.