Possible engine malfunctions (VAZ-2115)

Possible engine malfunctions, their causes and solutions

Cause of malfunction	Method of elimination
The engine won't start
No pressure in the fuel rail:	Please do the following:
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 (EMS)
The engine runs erratically or stalls while driving
Insufficient fuel pressure in the engine fuel line (rail)	Cm. "The engine won't start"
The idle speed control valve is faulty	Replace the idle air control valve
Air leakage through the engine crankcase ventilation hoses and the hose connecting the intake manifold to the brake booster	Tighten the mounting clamps, replace damaged hoses
Clearances between the tappets and camshaft cams are damaged	Adjust the valve clearances
The ignition system is faulty	See section "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 fuel pressure in the engine fuel line (rail)	See malfunction "The engine won't start"
The air filter is dirty	Replace the filter element
The ignition system is faulty	See section "Engine management system"
Clearances between the tappets and camshaft cams are damaged	Adjust the valve clearances
Insufficient compression - below 1 MPa (10 kgf/cm²):	Please do the following:
broken or stuck piston rings	replace the parts
poor valve seating	replace damaged valves, polish seats
excessive wear of cylinders and piston rings clean rings and piston grooves from carbon deposits damaged	replace pistons, bore and hone cylinder block
Increased fuel consumption
Increased resistance to vehicle movement	Check and adjust tire pressure, brake system, and steering wheel alignment
The ignition system is faulty	See section "Engine management system"
Injectors are faulty. Fuel leaks in connections	Cm. "Power supply system". Tighten the pipe connections
Use of low quality fuel	Fill with recommended fuel
Knocking of crankshaft main bearings
Usually a dull, metallic knock. It is detected when the throttle valves are 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
Too early ignition	Adjust the ignition timing
Insufficient oil pressure	See malfunction "Insufficient oil pressure at idle"
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 thrust half rings and crankshaft	Replace the thrust half rings with new ones or with increased thickness, 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 at idle"
Excessive clearance between the crankshaft journals and the bearings	Replace the bearings and grind the journals
Knocking of pistons
The knock is usually muffled and quiet; 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
Knocking of intake and exhaust valves
Excessive valve clearances cause a characteristic knocking noise, usually at regular intervals; its frequency is less than the frequency of any other knock in the engine, since the valves are driven by the camshaft, the rotation frequency of which is half the rotation frequency of the crankshaft
Increased valve clearances	Adjust the gaps
Valve spring failure	Replace the spring
Excessive clearance between valve and guide bushing	Replace worn parts
Camshaft cam wear	Replace the camshaft and adjusting washers
Insufficient oil pressure at idle with a warm engine
Foreign particles entering the oil pressure reducing valve	Clean the valve from foreign particles and burrs, wash the oil pump
Oil pressure reaction valve sticking	Replace the valve
The oil pump gears are worn out	Repair the oil pump
Excessive clearance between the bearings and the main journals of the crankshaft	Grind the journals and replace the bearings
Excessive clearance between journals and camshaft bearing housings	Replace the camshaft or cylinder head with bearing housings
Use of motor oil of the wrong brand and quality	Change the oil to others, recommended by the manufacturer.
Excessive oil pressure on a warm engine
Oil pressure relief valve sticking	Replace the valve
The oil pressure reducing valve spring has a higher rigidity	Replace the spring
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 the cylinders and replace the pistons and rings
Broken piston rings	Replace the rings
Coking of the slots in the oil scraper rings or grooves in the piston grooves due to the use of non-recommended oil	Clean the slots and grooves from carbon deposits, change the engine oil recommended by the manufacturer.
Worn or damaged valve stem seals	Replace the valve stem seals
Increased wear of valve stems or guide bushings	Replace valves, repair cylinder head
Rapid drop of liquid in the expansion tank
The radiator is damaged	Repair or replace the radiator
Damage to hoses or gaskets in pipeline connections, loose clamps	Replace damaged hoses or gaskets, tighten hose clamps
Leaking liquid from a tap or heater radiator	Replace the faucet or radiator
Leaking fluid through the coolant pump seal	Replace the seal
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
Liquid leakage through microcracks in the coolant pump housing, in the cooling jacket outlet pipe, in the thermostat, expansion tank or inlet pipe	Check for leaks; if cracks are found, replace damaged parts; minor leaks can be eliminated by adding a sealant of the NIISS-1 type to the coolant
Deformation of the coolant pump inlet pipe flange	Replace the supply pipe
Low opening pressure of the expansion tank cap valve	Check the plug and replace if necessary