Possible engine malfunctions, their causes and solutions
| Cause of malfunction | Method of elimination |
| The engine won't start | |
| No fuel pressure in the rail: | |
| fuel lines are clogged | Flush and blow out the fuel tank and fuel lines |
| the fuel pump is faulty | Replace the pump |
| the fuel filter is clogged | Replace the filter |
| the fuel pressure regulator is faulty | Check the regulator, replace the faulty one |
| The ignition system is faulty | Cm. Engine management system |
| Engine runs rough or stalls at idle | |
| Insufficient pressure in the fuel rail | See the fault "Engine does not start" |
| The idle speed control valve is faulty | Replace the idle air control valve |
| Air leakage through the engine crankcase ventilation hose and the hose connecting the intake pipe to the brake booster | Tighten the mounting clamps, replace damaged hoses |
| The ignition system is faulty | Cm. Engine management system |
| The engine does not develop full power and is not responsive enough | |
| Incomplete throttle opening | Adjust the throttle actuator |
| Throttle position sensor is faulty | Replace the sensor |
| Insufficient pressure in the fuel rail | See the fault "Engine does not start" |
| The air filter is dirty | Replace the filter element |
| The ignition system is faulty | Cm. Engine management system |
| Insufficient compression - below 1 MPa (10 kgf/cm²): | |
| the cylinder head gasket is blown | Replace the gasket |
| burnt pistons, broken or stuck piston rings | Clean the rings and piston grooves from carbon deposits, replace damaged rings and pistons |
| poor valve seating | Replace damaged valves, polish seats |
| excessive wear of cylinders and piston rings | Replace pistons, bore and hone cylinders |
| Insufficient oil pressure in a warm engine | |
| Using the wrong grade of oil | Replace the oil with the recommended one |
| Dilution or foaming of oil due to penetration of fuel or coolant into the oil pan | Eliminate causes of fuel or coolant leakage. Change oil |
| Contamination of the working cavity or wear of the oil pump parts | Flush or repair the oil pump |
| Clogged oil filter | Replace the oil filter |
| Loose or clogged oil pan | Secure the oil receiver, wash its filter |
| Increased clearance between main and connecting rod bearing shells and crankshaft journals | Grind the journals and replace the bearings |
| Cracks, pores in the walls of the cylinder block oil channels or clogged oil lines | Repair the cylinder block. If the defect cannot be eliminated, replace the block |
| Loose or missing oil channel plugs | Restore the tightness of the plugs, install missing plugs |
| Knocking of crankshaft main bearings | |
| Usually a dull, metallic knock. It is detected when the throttle valve is opened sharply at idle. Its frequency increases with increasing crankshaft speed. Excessive axial clearance of the crankshaft causes a sharper knock with uneven intervals, especially noticeable with a smooth increase and decrease in crankshaft speed | |
| Insufficient oil pressure | See fault "Insufficient oil pressure in warm engine" |
| The flywheel mounting bolts are loose | Tighten the bolts to the recommended torque |
| Increased clearance between journals and main bearing shells | Grind the journals and replace the bearings |
| Increased clearance between the thrust flanges of the center main bearing shells and the crankshaft | Replace the center main bearing shells with new ones, check the clearance |
| Knocking of connecting rod bearings | |
| Usually the knock of connecting rod bearings is sharper than the knock of main bearings. It can be heard at idle speed of the engine when the throttle valves are opened sharply. The place of knocking can be easily determined by disconnecting the spark plugs one by one | |
| Insufficient oil pressure | See fault "Insufficient oil pressure in warm engine" |
| Excessive clearance between the crankshaft journals and the bearings | Replace the bearings and grind the journals |
| Knocking of pistons | |
| The knock is usually not loud, but muffled; is caused by the piston "beating" in the cylinder. It is best heard at low crankshaft speed and under load | |
| Increased clearance between pistons and cylinders | Replace pistons, bore and hone cylinders |
| Excessive clearance between piston rings and piston grooves | Replace rings or pistons with rings |
| The piston is installed incorrectly (the piston pin hole is offset towards the left side of the engine) | Install the piston correctly |
| Increased noise from the valve timing mechanism | |
| Low oil pressure in the lubrication system | See fault "Insufficient oil pressure in warm engine" |
| Valve spring failure | Replace the spring |
| Excessive clearance between the valve stem and the guide bushing caused by wear | Install the valve of the next repair size, reaming the hole of its guide bushing accordingly |
| Camshaft cam wear | Replace the camshaft |
| Loosening of parts driven by the camshaft | Check and tighten the fasteners if necessary |
| A knock on a cold engine, audible for two to three minutes after starting and increasing in intensity as the crankshaft speed increases | |
| Increased clearance between pistons and cylinders | Piston knocking that disappears after the engine warms up is not a sign of a malfunction. If the knocking is constant, replace the pistons, bore and hone the cylinders |
| Brief knocking sounds immediately after starting the engine | |
| Using the wrong grade of oil (with reduced viscosity) | Replace the oil with the recommended one |
| Increased crankshaft axial clearance | Replace the center main bearing shells |
| Increased clearance in the front main bearing | Replace the front main bearing shells |
| Knocking in a warm engine at idle speed | |
| Loose or worn accessory drive belt | Adjust the belt tension or replace it |
| Noise from the timing mechanism parts | See fault "Increased noise of the valve timing mechanism" |
| Using the wrong grade of oil | Replace the oil with the recommended one |
| Increased clearances between piston pins and piston boss holes | Replace pistons and pins |
| Increased clearances between the crankshaft journals and the bearings | Replace the bearings and grind the journals |
| The axes of the upper and lower connecting rod heads are not parallel | Replace the connecting rod |
| The piston is installed incorrectly (the piston pin hole is offset towards the left side of the engine) | Install the piston correctly |
| Loud knocking in a warm engine when the crankshaft speed increases | |
| Torsional vibration damper or pulley hub failure | Replace damaged parts |
| The accessory drive belt is over-tightened or has cracks or breaks | Adjust the belt tension, replace the damaged belt |
| The flywheel mount is loose | Tighten the flywheel mounting bolts to the specified torque |
| Excessive increase in clearances between the connecting rod and main bearing shells of the crankshaft | Regrind the journals to the repair size and replace the liners |
| Increased engine vibration | |
| Crankshaft imbalance | Remove and balance the crankshaft |
| Uneven compression values in cylinders | Cm. Checking the compression in the cylinders |
| The powertrain suspension mounts are severely worn or hardened | Replace the pillows |
| The vibration damper or pulleys are loose | Tighten the fasteners |
| Engine detonation knocks when operating under load | |
| Using low octane gasoline | Fill with gasoline of the appropriate octane rating |
| The electronic engine control unit is faulty | Replace the block |
| Increased oil consumption | |
| Oil leaking through engine seals | Tighten the fasteners or replace the gaskets and seals |
| The crankcase ventilation system is clogged | Flush the crankcase ventilation system components |
| Wear of piston rings or engine cylinders | Rebore cylinders, replace pistons and rings |
| Broken piston rings | Replace the rings |
| Coking of oil scraper rings or grooves in piston grooves due to the use of non-recommended oil | Clean the rings and grooves from carbon deposits, replace the engine oil with the recommended one |
| Worn or damaged valve stem seals | Replace the valve stem seals |
| Increased wear of valve stems or guide bushings | Replace valves, repair cylinder head |
| Engine overheating | |
| Insufficient amount of fluid in the cooling system | Add coolant to the cooling system |
| The outer surface of the radiator is heavily contaminated | Clean the outer surface of the radiator with a jet of water |
| Thermostat is faulty | Replace Thermostat |
| The electric fan of the cooling system is faulty | Check the fan motor, its switch and relay, replace faulty units |
| The expansion tank cap valve is faulty (is constantly open, which is why the system is under atmospheric pressure) | Replace the expansion tank cap |
| Using low octane gasoline | Fill with gasoline of the appropriate octane rating |
| Rapid drop in fluid level in expansion tank | |
| The radiator is damaged | Repair the radiator or replace it |
| Damage to hoses or gaskets in pipeline connections, loose clamps | Replace damaged hoses or gaskets, tighten hose clamps |
| Fluid leaking through water pump seal | Repair the water pump |
| The cylinder head gasket is damaged | Replace the gasket |
| Fluid leakage through microcracks in the block or cylinder head | Check the tightness of the block and cylinder head; if cracks are found, replace damaged parts |
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