P0308

P0308 means cylinder 8 is misfiring, restricting the diagnosis to V8s, V10s, and V12s. Standard misfire flow: plug read, coil swap with an adjacent same-bank cylinder, plug swap, compression test, injector flow test. Cylinder 8 is typically the rear-most cylinder on one bank, which makes it the hardest to access on most longitudinal V8s — on a Ford modular 4.6L/5.4L, cylinder 8 is the rear-most cylinder on the left (driver's) bank, sitting partway under the cowl. On a GM LS V8, cylinder 8 is the rear-most cylinder on the left (driver's) bank. On a Chrysler Hemi, cylinder 8 is the rear-most cylinder on the left bank. The rear cylinders on a longitudinal V8 are exposed to the most heat soak and the longest exhaust manifold runs, which means they fail coils, plugs, and exhaust manifold studs first — budget extra labor on a P0308 just to get to the part.

Vehicle-specific patterns: 2004-2010 Ford F-150/Expedition/Navigator 5.4L 3V Triton is the most common P0308 in North America — same triple-threat as the other left-bank misfires (stuck plugs, cam phaser rattle, carbon-tracked coil boots), with the added wrinkle that cylinder 8 is buried under the cowl and adds 0.5-1.0 hr of labor over the front cylinders. 2007-2014 GM 5.3L/6.0L with Active Fuel Management throws P0308 from collapsed AFM lifters on the deactivated cylinders. 2003-2008 Dodge Ram/Durango 5.7L Hemi commonly throws P0308 from a known exhaust manifold bolt failure on the rear-most cylinders, causing a localized exhaust leak that confuses the O2 sensor into commanding a lean condition specifically on cylinder 8. 2006-2010 Mercedes-Benz M273 5.5L V8 throws P0308 from the same balance-shaft wear pattern as P0306. Estimated repair: $80 (single coil + extended labor) to $4,500+ (AFM delete or balance-shaft on the M273).