| Engine misfire with abnormal internal lower engine noises. | Worn crankshaft bearings Loose or out of specification engine flywheel | Replace the crankshaft and bearings as required. Repair or replace the flywheel as required. |
| Worn piston rings (Oil consumption may or may not cause the engine to misfire.) | Inspect the cylinder for a loss of compression. Repair or replace as required. |
| Worn crankshaft thrust bearings | Replace the crankshaft and bearings as required |
| Engine misfire with abnormal valve train noise. | Stuck valves. (Carbon buildup on the valve stem) | Repair or replace as required |
| Excessive worn or mis-aligned timing chain Out of specification valve clearances | Replace the timing chain and sprocket as required. |
| Worn camshaft lobes. | Replace the camshaft and valve lifters. |
| Engine misfire with coolant consumption | Faulty cylinder head gasket or other damage to the cylinder head and engine block cooling system. Coolant consumption may or may not cause the engine to overheat. | Inspect the cylinder head and engine block for damage to the coolant passages and/or a faulty head gasket. Repair or replace as required. |
| Engine misfire with excessive oil consumption | Worn valves, guides and/or valve stem oil seals. | Repair or replace as required. |
| Worn piston rings. (Oil consumption may or may not cause the engine to misfire) | Inspect the cylinder for a loss of compression. Repair or replace as required. |
| Engine noise on start-up, but only lasting a few seconds. (Check and compare with known good vehicle to determine normal condition.) | Incorrect oil viscosity | Drain the oil. Install the correct viscosity oil. |
| Worn crankshaft thrust bearing. | Inspect the thrust bearing and crankshaft. Repair or replace as required. |
| Upper engine noise, regardless of engine speed. | Low oil pressure | Repair or replace as required. |
| Broken valve spring. | Replace the valve spring. |
| Worn or dirty valve lifters. | Replace the valve lifters. |
| Stetched or broken timing chain and/or damaged sprocket teeth. | Replace the timing chain and sprockets. |
| Worn timing chain tensioner, if applicable. | Replace the timing chain tensioner as required. |
| Worn camshaft lobes. | Inspect the camshaft lobes. Replace the timing camshaft and valve lifters as required. |
| Out of specification valve clearances Worn valve guides or valve stems. | Inspect the valves and valve guides, then repair or replace as required. |
| Stuck valves. (Carbon on the valve stem or valve seat may cause the valve to stay open. | Inspect the valves and valve guides, then repair or replace as required. |
| Worn drive belt, idler, tensioner and bearing. | Replace as required |
| Lower engine noise, regardless of engine speed | Low oil pressure | Repair or replace as required |
| Loose or damaged flywheel. | Repair or replace the flywheel. |
| Damaged oil pan, contacting the oil pump screen. | Inspect the oil pan. Inspect the oil pump screen. Repair or replace as required. |
| Oil pump screen loose, damaged or restricted. | Inspect the oil pump screen. Repair or replace as required. |
| Excessive piston-to-cylinder bore clearance. | Inspect the piston, piston pin and cylinder bore. Repair or replace as required. |
| Excessive piston pin-to-piston clearance | Inspect the piston, piston pin and the connecting rod. Repair or replace as required. |
| Excessive connecting rod bearing clearance | Inspect the following components and repair or replace as required. The connecting rod bearings. The connecting rods. The crankshaft pin journals. |
| Excessive crankshaft bearing clearance | Inspect the following components, and repair or replace as required. The crankshaft bearings. The crankshaft main journals. The cylinder block |
| Incorrect piston, piston pin and connecting rod installation | Verify the piston pins and connecting rods are installed correctly. Repair as required. |
| Engine noise under load | Low oil pressure | Repair or replace as required. |
| Excessive connecting rod bearing clearance | Inspect the following components and repair or replace as required: The connecting rod bearings. The connecting rods. The crankshaft |
| Excessive crankshaft bearing clearance | Inspect the following components, and repair or replace as required. The crankshaft bearings. The crankshaft main journals. The cylinder block. |
| Engine will not crank-crankshaft will not rotate | Hydraulically locked cylinder Coolant/antifreeze in cylinder. Oil in cylinder. Fuel in cylinder | Remove spark plugs and check for fluid. Inspect for broken head gasket. Inspect for cracked engine block or cylinder head. Inspect for a sticking fuel injector and/or leaking fuel regulator. |
| Broken timing chain and/or timing chain and/or timing chain gears. | Inspect timing chain and gears. Repair as required. |
| Material in cylinder Broken valve Piston material Foreign material | Inspect cylinder for damaged components and/or foreign materials. Repair or replace as required. |
| Seized crankshaft or connecting rod bearings. | Inspect crankshaft and connecting rod bearing. Repair as required. |
| Bent or broken connecting rod. | Inspect connecting rods. Repair as required. |
| Broken crankshaft | Inspect crankshaft. Repair as required. |
