Engine Mechanical System - General Information: Troubleshooting

ENGINE MECHANICAL SYSTEM TROUBLESHOOTING

Symptom	Suspect area	Remedy
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	Replace the timing chain and sprocket as required.
	Worn camshaft lobes	Replace the camshaft.
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.
Engine misfire with excessive oil consumption	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.
	Stretched 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 camshaft as required.
	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 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 is not cranked. Crankshaft does 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 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.