2012 Jeep Wrangler: misfire or rough idle

Filed Nov 1, 2026 · Engine · TN

While driving my 2012 Jeep Wrangler Sport, the vehicle experienced a sudden and severe loss of engine power due to a cylinder failure on the left/driver-side cylinder head (cylinder #2). This defect causes the engine to experience persistent cylinder misfires, resulting in severe engine stumbling, hesitation, and a dangerous drop in acceleration capabilities. This creates an immediate safety hazard when attempting to merge onto high-speed highways, pull out into active traffic, or navigate intersections, as the vehicle cannot accelerate predictably to match traffic speeds. Furthermore, the persistent misfire causes unburned fuel to dump into the exhaust system, creating a secondary risk of catalytic converter overheating, damage to the exhaust system, and a potential engine bay fire hazard. This vehicle has only 86,000 original miles. This specific 3.6L Pentastar engine generation is subject to a widely documented manufacturing defect involving premature valve seat and head failure, which manifests as an unpredictable and sudden loss of motive power while the vehicle is in motion.

Filed Jul 7, 2026 · Engine · TX

The engine's cylinder head/valve train has failed internally, allowing combustion gases to enter the cooling system — confirmed via a chemical block test performed by a master automotive technician on November 29, 2024, which verified combustion gases present in the coolant. This is a widely documented defect on this engine and model year, related to valve seat erosion in the cylinder head. Symptoms first appeared in June 2018 as an unusual higher-pitched, stressed sound from the engine. Over time this progressed to recurring, confirmed misfires on cylinders 1, 2, 3, and 5 (diagnostic codes P0300, P0301, P0302, P0303, P0305) and a mixture control fault (P219B). The check engine light has intermittently stayed illuminated for months at a time, then gone off for extended periods while the same fault codes remain stored and confirmed by a diagnostic scanner — currently the light is off but the codes persist. The vehicle frequently runs rough enough that the engine must be turned off and restarted to temporarily return to closer-to-normal operation. Noticeable vibration is felt during much of this pattern. Spark plugs, ignition coils, oxygen sensors, and the PCV valve have all been inspected/replaced and ruled out as the cause on multiple occasions over more than a year, isolating the cause to the cylinder head itself. This creates a driveability and potential stalling/hesitation risk, though no crash, injury, or fire has occurred to date. The vehicle has not been formally inspected by the manufacturer, police, or an insurance representative. The affected component remains in the vehicle and is available for inspection upon request.

Filed Apr 1, 2026 · Engine · 71,756 miles · NY

The contact owns a 2012 Jeep Wrangler. The contact stated that while driving at 20 MPH, the check engine warning light illuminated. The local dealer was contacted, but the vehicle was not diagnosed or repaired. The vehicle was taken to an independent mechanic, where a scan was completed, and diagnostic trouble codes for the Emissions, engine misfire, timing chain, and crank position sensor failures were displayed. The manufacturer was not contacted. The failure mileage was approximately 71,756.

Filed Oct 29, 2025 · Engine · CA

The vehicle exhibits a persistent valvetrain ticking noise associated with the rocker/lifter/cam components of the 3.6L Pentastar V6. The engine makes a rhythmic metallic tapping at idle and during acceleration. The noise has progressively worsened, leading to rough idle and occasional misfires. This issue is documented in multiple Stellantis technical service bulletins (e.g., TSB 09-015-24 and TSB 09-011-25) which attribute the noise to hydraulic lash adjuster and cam/rocker wear. If unaddressed, the failure can cause camshaft damage, metal debris contamination, loss of power and potential engine stall, posing a safety risk. The vehicle is available for inspection. The problem has been confirmed by independent mechanics who recommend replacement of the rocker arms, lifters and camshaft to prevent catastrophic engine failure.

Filed Sep 30, 2025 · Engine · MO

The vehicle exhibits a persistent valvetrain ticking noise associated with the rocker/lifter/cam components of the 3.6L Pentastar V6. The engine makes a rhythmic metallic tapping at idle and during acceleration. The noise has progressively worsened, leading to rough idle and occasional misfires. This issue is documented in multiple Stellantis technical service bulletins (e.g., TSB 09-015-24 and TSB 09-011-25) which attribute the noise to hydraulic lash adjuster and cam/rocker wear. If unaddressed, the failure can cause camshaft damage, metal debris contamination, loss of power and potential engine stall, posing a safety risk. The vehicle is available for inspection. The problem has been confirmed by independent mechanics who recommend replacement of the rocker arms, lifters and camshaft to prevent catastrophic engine failure.

Filed Aug 31, 2025 · Engine · PA

Timing chain and misfire bank 1 and bank 2 crank shaft and crank sensor issues.

Filed Jun 6, 2025 · Engine · IL

I am reporting a persistent and safety-relevant defect in my 2012 Jeep Wrangler with the 3.6L Pentastar engine. The vehicle is experiencing misfires on multiple cylinders, especially cylinders 1 and 5, triggering codes P0300, P0301, and P0305. These misfires result in loss of power, hesitation, and rough idle, creating serious safety concerns during acceleration or highway driving. Despite replacing spark plugs, ignition coils, the crankshaft position sensor, purge valve, and both oxygen sensors, the problem continues. The vehicle has just 83,000 miles and is currently at a certified third-party repair facility. Multiple mechanics believe the issue stems from known defects in the left (Bank 1) cylinder head or valve train components—an issue Chrysler previously acknowledged via TSBs and a 10yr/150k mile extended warranty on select VINs. I contacted Jeep Cares and requested goodwill support, but they refused to even discuss the issue because my Jeep is not at a dealership. This leaves owners like me with limited, expensive options despite being affected by a well-documented defect. Jeep forums and independent shops have seen widespread misfire problems on early 3.6L Pentastar engines, especially 2012-2013 models. I urge the federal safety agency to investigate this pattern of failure. The misfires impact driveability and safety, and the manufacturer has not offered sufficient resolution or consistent support to affected customers. I’m happy to provide additional information, documentation, or diagnostics.

Filed Jun 11, 2021 · Engine · 90,000 miles · CT

The contact owns a 2012 Jeep Wrangler. The contact stated that the engine would misfire while driving at various speeds. Due to the failure, the vehicle would independently go into limp mode with the traction control and check engine warning lights illuminated. The contact had taken the vehicle to several unknown dealers and the engine misfire was acknowledged however, the cause of the failure was not determined. The manufacturer was not notified of the failure. The vehicle was not repaired. The failure mileage was approximately 90,000. The VIN was not available.

Filed Oct 14, 2019 · Engine · 85,915 miles · NY

Check engine light came on, with a p0302 #2 cylinder misfire reading. After replacing consumable parts (spark plugs, engine coil) reset engine light, the code p0302 returned after 15-20 miles driving. This issue is a well know problem with the 3.6l engine, and requires internal engine repair (lifters, rocker, and/or cylinder head replacement). An open service bulletin exists, but several jk vehicles with the similar issue cause parts backorder. If continue driving with this issue happens, more serious damage will result to the vehicle. As other complaints indicated, this situation should be classed as a recall.

Filed Oct 2, 2019 · Fuel system · 63,000 miles · OH

Engine light continues to come on after several repairs a sensor was replaced. The engine light is on again I have read several reviews as to cyclinders are misfiring this is a manufacturing problems that needs addressed by the manufacturer

Filed Sep 25, 2019 · Engine · 121,000 miles · CA

Check engine light illuminated, resulting in p0302 #2 cylinder misfire. After replacing consumable parts (spark plug, engine coil) reset engine light. Code returned after 20 miles driving. Dealer technicians indicate issue is #2 cylinder head needs replacement. Open service bulletin exists, however condition has affected enough jeep jku vehicles to result in part backorder. This presents an unsatisfactory condition as part may take weeks to months to obtain. No solution on temporary transportation available/ offered as result. Dealer indicates driving vehicle likely to worsen condition, and advises to keep until parts available. This situation should be classed as a recall and alternate transportation options available, especially in the southern california region.

Filed Nov 6, 2018 · Engine, Transmission · 20,000 miles · LA

Cylinder misfire less than 20k, heat chronically did not work, brought to dealer numerous times for no heat, ticking sound coming from motor. City driven vehicle. Major engine issue at 85k dealer telling me not a systemic problem with this particular vehicle. Extended warranty will not cover engine issues. Jeep over heating, no heat, replaced radiator twice at my own expense.