Intermittent
Test the vehicle under the same conditions that the customer reported in order to verify the system is operating properly.
Base Engine Misfire without Internal Engine Noises
| Cause | Correction |
|---|---|
| Abnormalities, severe cracking, bumps, or missing areas, in the accessory drive belt Abnormalities in the accessory drive system and/or components may cause engine RPM variations and lead to a misfire DTC. A misfire code may be present without an actual misfire condition. | Replace the drive belt. Refer to Drive Belt Replacement . |
| Worn, damaged, or mis-aligned accessory drive components or excessive pulley runout and may lead to a misfire DTC. A misfire code may be present without an actual misfire condition. | Inspect the components, repair or replace as required. |
| Loose or improperly installed engine flywheel or crankshaft balancer A misfire code may be present without an actual misfire condition. | Repair or replace the flywheel and/or balancer as required. Refer to Engine Flywheel Replacement or Crankshaft Balancer Replacement . |
| Restricted exhaust system A severe restriction in the exhaust flow can cause significant loss of engine performance and may set a DTC. Possible causes of restrictions include collapsed or dented pipes or plugged mufflers and/or catalytic converters. | Repair or replace as required. |
| Improperly installed or damaged vacuum hoses | Repair or replace as required. |
| Improper sealing between the intake manifold and cylinder heads, intake manifold and plenum duct, plenum duct and water crossover, water crossover and throttle body and/or pressure relief valve and intake manifold. | Replace the intake manifold, plenum duct, gaskets, cylinder heads, throttle body and/or pressure relief valve as required. |
| Improperly installed or damaged MAP sensor and/or seal The sealing grommet of the MAP sensor should not be torn or damaged. | Repair or replace the MAP sensor as required. |
| Improperly installed or damaged EVAP purge solenoid and/or O-ring seal | Repair or replace the EVAP purge solenoid as required. |
| Worn or loose followers, valve rocker arms The follower, valve rocker arm, roller bearing should be intact and in the proper position. | Replace the followers, valve rocker arms, as required. |
| Stuck valves Carbon buildup on the valve stem can cause the valve not to close properly. | Repair or replace as required. |
| Excessively worn or mis-aligned timing chain or chains | Replace the timing chain or chains and sprockets as required. |
| Worn camshaft lobes | Replace the camshaft or camshafts and SHLAs (valve lifters). |
| Excessive oil pressure A lubrication system with excessive oil pressure may lead to excessive valve lifter pump-up and loss of compression. | Perform an oil pressure test. Refer to Oil Pressure Diagnosis and Testing . Repair or replace the oil pump as required. |
| Faulty cylinder head gaskets and/or cracking or other damage to the cylinder heads and engine block cooling system passages. Refer to Diagnostic Starting Point - Vehicle . Coolant consumption may or may not cause the engine to overheat. | Inspect for spark plugs saturated by coolant. Refer to Spark Plug Inspection for the 3.6L engine. Inspect the cylinder heads, engine block, and/or head gaskets. Repair or replace as required. |
| Worn Piston Rings Oil consumption may or may not cause the engine to misfire. | Inspect the spark plugs for oil deposits. Refer to Spark Plug Inspection for the 3.6L engine. Inspect the cylinders for a loss of compression. Refer to Engine Compression Test . Perform cylinder leak down and compression testing to identify the cause. Repair or replace as required. |
| A damaged crankshaft reluctor wheel A damaged crankshaft reluctor wheel can result in different symptoms depending on the severity and location of the damage. Systems with SEVERE reluctor ring damage may exhibit periodic loss of crankshaft position, stop delivering a signal, and then re-sync the crankshaft position. Systems with SLIGHT reluctor ring damage may exhibit no loss of crankshaft position and no misfire may occur. However, a P0300 DTC may be set. | Replace the crankshaft as required. |
Base Engine Misfire with Abnormal Internal Lower Engine Noises
| Cause | Correction |
|---|---|
| Abnormalities, severe cracking, bumps or missing areas, in the accessory drive belt Abnormalities in the accessory drive system and/or components may cause engine RPM variations, noises similar to a faulty lower engine and also lead to a misfire condition. A misfire code may be present without an actual misfire condition. | Replace the drive belt. Refer to Drive Belt Replacement . |
| Worn, damaged, or mis-aligned accessory drive components or excessive pulley runout A misfire code may be present without an actual misfire condition. | Inspect the components, repair or replace as required. |
| Loose or improperly installed engine flywheel or crankshaft balancer A misfire code may be present without an actual misfire condition. | Repair or replace the engine flywheel and/or crankshaft balancer as required. Refer to Engine Flywheel Replacement or Crankshaft Balancer Replacement . |
| Worn or Broken Piston Rings Oil consumption may or may not cause the engine to misfire. | Inspect the spark plugs for oil deposits. Refer to Spark Plug Inspection for the 3.6L engine. Inspect the cylinders for a loss of compression. Refer to Engine Compression Test . Perform cylinder leak down and compression testing to determine the cause. Repair or replace as required. |
| Worn Crankshaft Thrust Bearings Severely worn thrust surfaces on the crankshaft and/or thrust bearing may permit fore and aft movement of the crankshaft and create a DTC without an actual misfire condition. | Replace the crankshaft and bearings as required. |
Base Engine Misfire with Coolant Consumption
| Cause | Correction |
|---|---|
| Faulty cylinder head gaskets and/or cracking or other damage to the cylinder heads and engine block cooling system passages. Refer to Diagnostic Starting Point - Vehicle . Coolant consumption may or may not cause the engine to overheat. | Inspect for spark plugs saturated by coolant. Refer to Spark Plug Inspection . Perform a cylinder leak down test. Inspect the cylinder heads and engine block for damage to the coolant passages and/or a faulty head gasket. Repair or replace as required. |
Base Engine Misfire with Excessive Oil Consumption
| Cause | Correction |
|---|---|
| Worn valves, valve guides and/or valve stem oil seals | Inspect the spark plugs for oil deposits. Refer to Spark Plug Inspection . Repair or replace as required. |
| Worn piston rings Oil consumption may or may not cause the engine to misfire. | Inspect the spark plugs for oil deposits. Refer to Spark Plug Inspection . Inspect the cylinders for a loss of compression. Refer to Engine Compression Test . Perform cylinder leak down and compression testing to determine the cause. Repair or replace as required. |
Engine Will Not Crank - Crankshaft Will Not Rotate
| Cause | Correction |
|---|---|
| Seized accessory drive system component | Remove the accessory drive belt or belts. Rotate the crankshaft by hand at the crankshaft balancer or the engine flywheel location. Repair or replace as required. |
| Hydraulically locked cylinder Coolant/antifreeze in cylinder Oil in cylinder Fuel in cylinder | Remove the spark plugs and check for fluid. Inspect for broken head gasket or gaskets. Inspect for cracked engine block or cylinder head. Inspect for a sticking fuel injector. Repair or replace as required. |
| Seized automatic transmission torque converter | Remove the torque converter bolts. Rotate the crankshaft by hand at the crankshaft balancer or the engine flywheel location. Repair or replace as required. |
| Material in cylinder Broken valve Piston material Foreign material | Inspect the cylinder for damaged components and/or foreign materials. Repair or replace as required. |
| Seized crankshaft or connecting rod bearings | Inspect the crankshaft and the connecting rod bearings. Repair as required. |
| Bent or broken connecting rod | Inspect the connecting rods. Repair as required. |
| Broken crankshaft | Inspect the crankshaft. Repair as required. |
| Seized or broken camshaft | Inspect the camshaft or camshafts. Inspect the cylinder head camshaft journals for damage. Repair as required. |
| Seized or broken balance shaft | Inspect the balance shaft. Inspect the block for damaged balance shaft bearings. Repair as required. |
| Seized or broken camshaft timing components | Inspect the following sprockets: The crankshaft sprocket The exhaust sprockets The intake sprockets Inspect the following chains: The primary camshaft drive chain The secondary camshaft drive chains Inspect the following guides: The lower primary camshaft drive chain guide The upper primary camshaft drive chain guides Inspect the secondary camshaft drive chain shoe. Inspect the following tensioners: The primary camshaft drive chain tensioner The secondary camshaft drive chain tensioners Repair as required. |
| Seized or broken valve train components | Inspect the followers, rocker arms. Inspect the lifters. Inspect the valves. Inspect the valve springs. Repair as required. |
Coolant in Combustion Chamber
| Cause | Correction |
|---|---|
| DEFINITION: Excessive white smoke and/or coolant type odor coming from the exhaust pipe may indicate coolant in the combustion chamber. Low coolant levels, an inoperative cooling fan, or a faulty thermostat may lead to an "overtemperature" condition which may cause engine component damage. A slower than normal cranking speed may indicate coolant entering the combustion chamber. Refer to Engine Will Not Crank - Crankshaft Will Not Rotate . Remove the spark plugs and inspect for spark plugs saturated by coolant or coolant in the cylinder bore. Inspect by performing a Cylinder Leakage Test . During this test, excessive air bubbles within the coolant may indicate a faulty gasket or damaged component. Inspect by performing a cylinder compression test. Two cylinders "side-by-side" on the engine block, with low compression, may indicate a failed cylinder head gasket. Refer to Engine Compression Test . | |
| Cracked intake manifold or failed gasket | Replace the components as required. |
| Faulty cylinder head gasket | Replace the head gasket and components as required. Refer to Cylinder Head Cleaning and Inspection and Cylinder Head Replacement - Left Side or Cylinder Head Replacement - Right Side . |
| Warped cylinder head | Machine the cylinder head to the proper flatness, if applicable and replace the cylinder head gasket. Refer to Cylinder Head Cleaning and Inspection . |
| Cracked cylinder head | Replace the cylinder head and gasket. |
| Cracked cylinder liner or engine block | Replace the components as required. |
| Cylinder head or engine block porosity | Replace the components as required. |
Coolant in Engine Oil
| Cause | Correction |
|---|---|
| DEFINITION: Foamy or discolored oil or an engine oil "overfill" condition may indicate coolant entering the engine crankcase. Low coolant levels, an inoperative cooling fan, or a faulty thermostat may lead to an "overtemperature" condition which may cause engine component damage. Contaminated engine oil and oil filter should be changed. Inspect the oil for excessive foaming or an overfill condition. Oil diluted by coolant may not properly lubricate the crankshaft bearings and may lead to component damage. Refer to Lower Engine Noise, Regardless of Engine Speed . Inspect by performing a Cylinder Leakage Test . During this test, excessive air bubbles within the cooling system may indicate a faulty gasket or damaged component. Inspect by performing a cylinder compression test. Two cylinders "side-by-side" on the engine block with low compression may indicate a failed cylinder head gasket. Refer to Engine Compression Test . | |
| Faulty external engine oil cooler | Replace the components as required. |
| Faulty cylinder head gasket | Replace the head gasket and components as required. Refer to Cylinder Head Cleaning and Inspection and Cylinder Head Replacement - Left Side or Cylinder Head Replacement - Right Side . |
| Warped cylinder head | Machine the cylinder head to proper flatness, if applicable, and replace the cylinder head gasket. Refer to Cylinder Head Cleaning and Inspection . |
| Cracked cylinder head | Replace the cylinder head and gasket. |
| Cracked cylinder liner or engine block | Replace the components as required. |
| Cylinder head, block, or manifold porosity | Replace the components as required. |
Tools Required
J 39313 Spark Plug Port Adapter. See Special Tools .
A compression pressure test of the engine cylinders determines the condition of the rings, the valves and the head gasket.