Possible engine malfunctions, their causes and remedies
Cause of malfunction | Remedy |
Engine won't start | |
No fuel pressure in the rail: | |
clogged fuel lines | Flush and blow out the fuel tank and fuel lines |
fuel pump faulty | Replace pump |
clogged fuel filter | Replace filter |
faulty fuel pressure regulator | Check the regulator, replace the faulty one |
Faulty ignition system | See Engine management system |
Engine runs erratically or stalls at idle | |
Insufficient pressure in the fuel rail | See fault «Engine won't start» |
Faulty idle speed controller | Replace idle speed control |
Air leakage through the crankcase ventilation hose and the hose connecting the intake pipe to the vacuum brake booster | Tighten the fastening clamps, replace damaged hoses |
Faulty ignition system | See Engine management system |
The engine does not develop full power and is not throttled enough | |
Incomplete throttle opening | Adjust throttle actuator |
Faulty throttle position sensor | Replace sensor |
Insufficient pressure in the fuel rail | See fault «Engine won't start» |
Air filter dirty | Replace filter element |
Faulty ignition system | See Engine management system |
Insufficient compression - below 1 MPa (10 kgf/cm2): | |
blown cylinder head gasket | Replace gasket |
burnt pistons, breakage or occurrence of piston rings | Clean the rings and grooves of the pistons from carbon deposits, replace the damaged rings and the piston |
poor fit of valves to the seats | Replace damaged valves, grind seats |
excessive wear of cylinders and piston rings | Replace pistons, bore and honing cylinders |
Insufficient oil pressure in a warm engine | |
Using the wrong brand of oil | Change oil to recommended |
Thinning or foaming of oil due to fuel or coolant entering the oil sump | Eliminate the cause of fuel or coolant intrusion. Change oil |
Contamination of the working cavity or wear of the oil pump parts | Flush or repair the oil pump |
Clogged oil filter | Change oil filter |
Loose or clogged oil pickup | Fix the oil receiver, wash its filter |
Increased clearance between main and connecting rod bearing shells and crankshaft journals | Sand the necks and replace the liners |
Cracks, pores in the walls of the oil channels of the cylinder block or clogging of the oil lines | Repair the cylinder block. If it is impossible to eliminate the defect, replace the unit |
Loose installation of oil channel plugs or their absence | Restore the tightness of the plugs, install the missing plugs |
Knocking crankshaft bearings | |
Usually a dull tone, metallic. Detected when the throttle is suddenly opened at idle. Its frequency increases with an increase in the frequency of rotation of the crankshaft. Excessive axial clearance of the crankshaft causes a sharper knock with uneven intervals, especially noticeable with a smooth increase and decrease in the crankshaft speed | |
Insufficient oil pressure | See fault «Insufficient oil pressure in a warm engine» |
Loose flywheel bolts | Tighten the bolts to the recommended torque |
Increased clearance between journals and main bearing shells | Sand the necks and replace the liners |
Increased clearance between the thrust flanges of the middle main bearing shells and the crankshaft | Replace the middle main bearing shells with new ones, check the clearance |
Knocking rod bearings | |
Usually the knock of the connecting rod bearings is sharper than the knock of the main bearings. It is heard at idle speed of the engine with a sharp opening of the throttle valves. The place of knocking is easy to determine by turning off the spark plugs one by one | |
Insufficient oil pressure | See fault «Insufficient oil pressure in a warm engine» |
Excessive clearance between crankshaft journals and bearings | Replace bushings and grind necks |
The knock of pistons | |
The knock is usually not sonorous, muffled; called «beating» piston in the cylinder. It is best heard at low engine speeds and under load | |
Increased clearance between pistons and cylinders | Replace pistons, bore and honing cylinders |
Excessive clearance between piston rings and piston grooves | Replace rings or pistons with rings |
Piston installed incorrectly (Piston pin bore offset towards left side of engine) | Install the correct piston |
Increased noise of the gas distribution mechanism | |
Reduced oil pressure in the lubrication system | See fault «Insufficient oil pressure in a warm engine» |
Valve spring failure | Replace spring |
Excessive clearance between valve stem and guide bushing due to wear | Install the next oversize valve by reversing the valve guide hole accordingly |
Camshaft lobes wear | Replace camshaft |
Loose fastening of parts driven by the camshaft | Check and tighten fasteners if necessary |
Knocking on a cold engine, audible for two to three minutes after starting and increasing with increasing engine speed | |
Increased clearance between pistons and cylinders | Piston knocking that disappears after the engine warms up is not a sign of a malfunction. With constant knocking, replace the pistons, bore and honing the cylinders |
Intermittent knocking immediately after starting the engine | |
Using the wrong brand of oil (with reduced viscosity) | Change oil to recommended |
Increased axial clearance of the crankshaft | Replace middle main bearing shells |
Increased clearance in the front main bearing | Replace front main bearing shells |
Knocking in a warm engine at idle | |
Loose or worn accessory drive belt | Adjust belt tension or replace |
Noise of parts of the gas distribution mechanism | See fault «Increased noise of the gas distribution mechanism» |
Using the wrong brand of oil | Change oil to recommended |
Increased clearances between piston pins and bores in piston bosses | Replace pistons and pins |
Increased clearances between the connecting rod journals of the crankshaft and liners | Replace bushings and grind necks |
The axes of the upper and lower connecting rod heads are not parallel | Replace connecting rod |
Piston installed incorrectly (Piston pin bore offset towards left side of engine) | Install the correct piston |
Strong knocking in a warm engine with an increase in the crankshaft speed | |
Vibration damper or pulley hub failure | Replace damaged parts |
Accessory drive belt is too tight or cracked or broken | Adjust belt tension, replace damaged belt |
Loose flywheel | Tighten the flywheel mounting bolts to the required torque |
Excessive increase in clearances between the shells of the connecting rod and main bearings of the crankshaft | Regrind the necks to repair size and replace the liners |
Increased engine vibration | |
Crankshaft imbalance | Remove and balance the crankshaft |
Unequal compression values in the cylinders | See Cylinder compression check |
Powertrain suspension pads severely worn or hardened | Change your pillows |
Loose vibration damper or pulleys | Tighten fasteners |
Engine knock noises when under load | |
Using low octane gasoline | Fill with gasoline with the correct octane rating |
Faulty electronic engine control unit | Replace Block |
Increased oil consumption | |
Oil leakage through engine seals | Tighten fasteners or replace gaskets and seals |
Clogged crankcase ventilation system | Flush the parts of the crankcase ventilation system |
Worn piston rings or engine cylinders | Rebore cylinders, replace pistons and rings |
Breakage of piston rings | Replace rings |
Coking of oil scraper rings or grooves in the 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 |
Worn or damaged valve stem seals | Replace valve stem seals |
Increased wear on valve stems or guide bushings | Replace valves, rebuild 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 soiled | Clean the outer surface of the radiator with a jet of water |
Faulty thermostat | Replace thermostat |
Faulty cooling fan | Check the fan motor, the sensor for turning it on and the relay, replace the faulty components |
Expansion tank plug valve defective (permanently open, causing the system to be at atmospheric pressure) | Replace expansion tank cap |
Using low octane gasoline | Fill with gasoline with the correct octane rating |
Rapid drop in fluid level in expansion tank | |
Damaged radiator | Repair or replace radiator |
Damage to hoses or gaskets in pipe connections, loose clamps | Replace damaged hoses or gaskets, tighten hose clamps |
Fluid leakage through the water pump seal | Repair water pump |
Damaged cylinder head gasket | Replace 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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