Possible engine malfunctions, their causes and methods of elimination (VAZ-21011)

Cause	Method of elimination
The engine does not start
No fuel in carburetor:
– fuel lines or filters of the carburetor and fuel pump are clogged	– flush and blow out the fuel tank, fuel lines and filters
- the fuel pump is faulty	– check the operation of the pump and replace damaged parts
The ignition system is faulty	Cm. subsection 5.4
The carburetor air damper remains closed during the first flashes in the cylinders	Fix the leak in the carburetor starter
Engine runs rough or stalls at idle
Engine idle speed adjustment is out of adjustment	Adjust idle speed
Air leakage through a damaged drainage tube	Replace the drain tube
Air leakage through gaskets in the connections of the intake manifold to the carburetor or to the cylinder head	Tighten the mounting nuts or replace the gaskets
The clearances between the levers and the camshaft cams are damaged	Adjust the gaps
The carburetor is faulty:
- the jets or channels of the carburetor are clogged	– blow out the jets and channels with compressed air
- water in the carburetor	- remove water from the carburetor, drain sediment from the fuel tank
– the tightness of the diaphragm of the starting device is broken	replace the diaphragm
The ignition system is faulty	Cm. subsection 5.4
The engine does not develop full power and does not have sufficient throttle response
Incomplete opening of the carburetor throttle valves	Adjust the throttle actuators
The air filter is dirty	Replace the filter element
The ignition system is faulty	Cm. subsection 5.4
The fuel pump is faulty	Check the pump operation and replace damaged parts
The carburetor is faulty:
– the accelerator pump is faulty	– check the pump performance, replace damaged parts
- the main jets are clogged	– blow out the jets with compressed air
– the air damper is not fully open	– adjust the damper drive
– the fuel level in the float chamber does not correspond to the norm	– adjust the float setting
The clearances between the levers and the camshaft cams are damaged	Adjust the gaps
Insufficient compression - below 1 MPa (10 kgf/cm²):
- the cylinder head gasket is broken	- 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 seat fit	– replace damaged valves, polish seats
- excessive wear of cylinders and piston rings	– replace pistons, bore and hone cylinders
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
Too early ignition	Adjust the ignition timing
Insufficient oil pressure	Cm. below
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 thicker ones
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 valve is opened sharply. The place of knocking is easy to determine by disconnecting the spark plugs one by one
Insufficient oil pressure	Cm. below
Excessive clearance between the crankshaft journals and the bearings	Replace the bearings and grind the journals
Knocking of pistons
This knock is usually muffled and quiet: it is caused by the piston "beating" in the cylinder. It is best heard at low crankshaft speeds 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
Operating with increased valve clearances causes a characteristic knocking sound, usually at regular intervals; its frequency is lower than 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 clearances between the levers and camshaft cams	Adjust the gaps
Valve spring failure	Replace the spring
Excessive clearance between valve stem and valve guide	Replace worn parts
Camshaft cam wear	Replace the camshaft and valve levers
Unscrewing the locknut of the adjusting bolt	Adjust the clearance between the lever and the camshaft cam, tighten the lock nut
Excessive camshaft drive chain noise
From the general engine noise, the noise of the camshaft drive chain stands out when gaps appear between the engagement elements and is clearly audible at low crankshaft rotation speeds.
The chain has become loose due to wear	Tighten the chain
Chain tensioner shoe or guide shoe failure	Replace the tensioner shoe or guide
Chain tensioner plunger rod sticking	Eliminate the jam
Insufficient oil pressure at idle with a warm engine
Foreign particles entering the oil pump pressure relief valve	Clean the valve from foreign particles and burrs, wash the oil pump
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
Oil pressure relief valve sticking	Replace the valve
Use of motor oil of the wrong brand and quality	Replace the oil with another one recommended in subsection 14.3
Excessive oil pressure on a warm engine
Oil pump pressure relief valve sticking	Replace the valve
Increased oil consumption
Oil leaking through engine seals	Tighten the fasteners or replace the gaskets and seals
Wear of piston rings and pistons 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 in the piston grooves	Clean the slots and grooves from carbon deposits
Worn or damaged valve stem seals	Replace the valve stem seals
Increased wear of valve stems or guide bushings	Replace valves, repair cylinder head
Increased fuel consumption
The air damper is not fully open	Adjust the damper drive
Increased vehicle drag	Check and adjust tire pressure, brake system, wheel alignment
Incorrect ignition timing	Adjust the ignition timing
The vacuum regulator of the ignition distributor is faulty	Replace the vacuum regulator or distributor
High fuel level in carburetor:
– the needle valve or its gasket is not sealed properly	– check for foreign particles between the needle and the valve seat, replace the valve or gasket if necessary
- sticking or friction preventing normal movement of the float, float leakage	– check and replace the float if necessary
The carburetor air jets are clogged	Clean the jets
Engine overheating
Weak tension of the pump and generator drive belt	Adjust the belt tension
Insufficient amount of fluid in the cooling system	Add coolant to the cooling system
Incorrect ignition timing	Adjust the ignition timing
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
Faulty radiator plug valve (opening pressure less than 0.05 MPa (0.5 kgf/cm²)	Replace the plug
Coolant pump is faulty	Check the pump operation, replace it or repair it
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	Replace damaged hoses or gaskets
Leaking liquid from the heater tap	Replace the faucet
The hose clamps are loose	Tighten the clamps
Leaking fluid through the coolant pump seal	Replace the seal
The radiator cap or gasket is damaged	Replace the plug
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
Leakage of fluid through microcracks in the housing or cover of the coolant pump, 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