Engine diagnostics performed during operation (Hyundai Elantra J1)

Increased content of harmful substances in exhaust gases

Measurements show high concentrations of harmful substances; a rotten egg smell may occur. The appearance of an unpleasant odor is not necessarily a sign of improper combustion.

Perform circuit diagnostics. Check:

• no leaks in vacuum lines;
• cooling system and fan;
• remove carbon deposits using engine cleaner.

If high NOx concentrations are detected during measurements, check for reasons why the fuel mixture is too lean or the combustion temperature is below normal.

If high concentrations of hydrocarbons and CO are detected during measurements or the exhaust has an unpleasant odor, check for reasons why the working mixture is too rich. These include:

• fuel pressure deviation from normal (fuel pump);
• sticking or clogging of the positive crankcase ventilation system valve or clogging of the system hose;
• incorrect installation of spark plugs, spark plug wires or ignition system components;
• incorrect ignition timing;
• incorrect installation of the fuel tank cap.

Self-ignition in cylinders

The engine continues to run after the ignition is turned off, but very unevenly. If the engine runs smoothly, check the ignition switch.

Inspect the spark plugs.

Adjust the ignition timing.

Check the injector for leaks;

Apply 12V to the fuel pump test terminal to turn it on. Increase the pressure in the fuel system;

Inspect the injector and throttle body for fuel leaks.

Backfires

Fuel ignition in the intake manifold or in the exhaust system with a loud noise.

Check:

• ignition coil output voltage;
• ignition order, paying attention to the distributor cap, spark plug wires, their correct installation;
• setting the ignition timing;
• serviceability of spark plugs, spark plug wires and boots.

Check the compression (detection of sticking or loose valves).

Check the valve timing.

Interruptions, failures

A temporary loss of engine sensitivity to pressing the gas pedal can occur at any speed. Usually most noticeable when trying to start moving after stopping. In severe cases, it may lead to engine failure.

Check:

• fuel pressure (fuel pump);
• fuel for the presence of water;
• setting the ignition timing;
• generator output voltage. The generator requires repair if the voltage is below 9 V or above 1.6 V;
• to break the connection line to the ignition system ground.

Skipping Flashes

Constant jolting during engine operation, usually increasing with increasing engine load. The exhaust pipe constantly makes a splashing sound when idling or at low speeds.

Conduct a thorough inspection. If you suspect that misfires at idle or while driving are caused by a malfunction of the ignition system, perform the appropriate checks.



Identify the non-working cylinder. To do this:

• Start the engine. Disconnect the idle air supply system actuator. Using the appropriate tool, disconnect one spark plug wire at a time.
• A drop in engine speed may occur when disconnecting the spark plug wire from each cylinder (at about 50 rpm) followed by uneven engine operation and even stalling. Turn off the engine, connect the idle air supply system actuator.
• If disconnecting a spark plug wire from one or more cylinders does not result in a drop in engine speed or does not result in a significant difference in the rate of drop in engine speed, check the suspected cylinder(s) for spark discharges using a suitable device. If there is a discharge, then unscrew the spark plug from this cylinder and check for cracks, wear, incorrect gap, burnt electrodes, and significant deposits.

Check the spark plug wire resistance (resistance should not exceed 30000 Ohm).

If the previous checks did not produce results, perform the following checks:

• inspect the ignition system for moisture, dust, and burning. Spray the spark plug wires with water mist to detect shorts;
• check the fuel system (clogged fuel filter, water in fuel, low pressure);
• check the compression;
• check that the spark plug wires are installed correctly.

Low fuel efficiency

Fuel economy measured in real-world road tests is significantly lower than expected. In addition, fuel efficiency is significantly lower than what the car previously achieved under the same conditions.

Check:

• thermostat for valve failure (always open) or deviation from a given temperature range;
• fuel pressure.

Please check:

• vacuum hoses for cracks, kinks and loose fittings;
• tire pressure;
• mass of transported goods;
• use of excessively high or frequent accelerations when driving.

Perform electrical circuit diagnostics.

Check the air filter for contamination.

Check the speedometer calibration.

Check the spark plug wires for cracks, hardening, and proper connection,

Check the ignition timing.

Remove the spark plugs, check for dirt and cracks, wear, gap changes, electrode burnout and significant deposits. Replace if necessary.

Check the compression.

Check the brakes for drag.

Recheck the fuel consumption with the tank filled with fuel.

Check for deposits in the exhaust system.

Uneven operation and engine stalling at idle

The engine runs unevenly at idle. In more serious cases, the vehicle may vibrate. It is also possible to change the rotation frequency (oscillations). In this case, the engine may stop. Deviation from normal rotation speed is possible.

Check:

• setting the ignition timing;
• compliance of the resistance of the sensor coil and contacts with the norm;
• injector for leaks;
• lack of loose connections of the ignition coil;
• no moisture under the distributor cap;
• absence of contamination and cracks in spark plugs, wear, gap changes, electrode burning and significant deposits.

RPM fluctuations and/or popping noises in the muffler

Fluctuations in engine power at a constant throttle opening at idle or when driving are subjectively felt as acceleration and deceleration of the car without changing the position of the gas pedal.



Check:

• setting the ignition timing;
• fuel filter on the fuel line for contamination and deposits;
• fuel pressure;
• generator output voltage (repair is necessary if the voltage is below 9 V or above 16 V).

Check the CO content in the exhaust gases using a suitable device. If the CO content is too low (below 0.3%), the air-fuel mixture is lean. This leads to difficulties in controlling the vehicle.

Remove the spark plugs. Check for contamination and cracks, wear, gap changes, electrode burnout and significant deposits. Also check the condition of the entire ignition system.

Loss of power, engine sluggishness, poor response to pedal input

The power developed by the engine is lower than expected. Complete or almost complete insensitivity of the car to partial pressing of the gas pedal.

Remove the air cleaner and check the degree of contamination of the air filter. Replace if necessary.

Check:

• setting the ignition timing;
• presence of contamination in the fuel filter and deviations of fuel pressure from the norm;
• the condition of the lines connecting the control unit to the engine ground.

Check the exhaust system for obstructions. To do this, do the following:

• with the engine running and at normal temperature, connect the vacuum gauge sensor to any suitable vacuum port in the intake manifold. At 1000 rpm, measure the vacuum:
• slowly increase the speed to 2500 rpm. Measure the vacuum when the speed is stable at 2500 rpm;
• if the vacuum level at 2500 rpm decreases by more than 21 kPa compared to the value measured at 1000 rpm, check the exhaust system for obstructions;
• disconnect the exhaust pipe from the engine and perform the procedures specified in the previous paragraphs. If the vacuum still drops more than 21 kPa, check the valve installation.

Check the generator output voltage. The generator requires repair if the voltage is below 9 V or above 16 V.



Check engine valve timing and compression.

Check the camshaft for wear.

Check the ignition voltage with a suitable device.

Engine detonation

A knocking noise, moderate to loud in intensity, usually increasing with acceleration. A sharp metallic sound that changes when the throttle valve is opened.

Check for overheating. Overheating may be due to:

• low coolant level;
• loosening of the coolant pump belt;
• restricted air or coolant flow through the radiator;
• faulty thermostat;
• faulty electric fan circuit;
• changes in the sensitivity of the coolant temperature sensor.

Check:

• fuel quality, its octane number;
• correct selection of spark plugs according to thermal conditions;
• setting the ignition timing;
• fuel system pressure (is there a fall);
• fuel system;
• correct adjustment of the gear shift system;
• correct selection of engine parts, such as camshaft, head, pistons, etc.

Remove carbon deposits using engine cleaner. Instructions for use are given on the packaging.

Increased oil consumption

Increased oil consumption may be caused by one of the following reasons:

• leakage in the lubrication system. Tighten threaded connections and/or replace gaskets and seals if necessary;
• incorrect determination of the oil level using the oil dipstick. When determining the oil level, place the vehicle on a level surface and wait for some time for the oil to drain into the crankcase.
• idle speed too low. If the engine idle speed is not controlled by the electrical unit, adjust the idle speed as required;
• worn out oil pump. Replace the oil pump;
• dirty oil filter. Replace the oil filter;
• the mesh filter on the oil pump inlet pipe has become loose or clogged. Clean and rinse the mesh filter.
• incorrect oil viscosity or thin oil;
• long periods of driving at high speeds or with a trailer usually results in increased oil consumption;
• malfunction in the forced crankcase ventilation system;
• wear of valve stem seals and/or valve guides;
• poorly ground, worn or broken piston rings. Allow the new piston rings to bed in for some time. Replace broken or worn piston rings if necessary;
• incorrect piston installation or incorrect size.

Low oil pressure

Low oil pressure can be caused by the following reasons:

• excessive clearance in the crankshaft bearings. Replace bearings if necessary;
• cracks, pores or plugs in the cylinder block channels. Repair or replace the unit;
• absence or incorrect installation of the lubrication system plug. Install plugs or replace if necessary;
• idle speed too low. Adjust idle speed as required.

Noise in the valve timing mechanism

Noise in the valve train may be caused by any of the following reasons:

• low oil pressure. Eliminate the cause;
• valve spring failures, valve sticking;
• worn, dirty or faulty valve lifters. Clean from dirt, check and replace if necessary;
• worn or defective timing shaft. Replace the shaft.

Knocking in a cold engine, lasting two to three minutes and/or increasing with increasing load

• The flywheel is touching the casing. Adjust the casing installation.
• Increased clearance between pistons and cylinders. Ream the block cylinders and hone to the repair size. Replace the piston. Piston knocking on a cold engine usually disappears after the engine warms up. The knocking of pistons of a cold engine, which disappears after 1-2 minutes, is acceptable.
• Bent connecting rod.

A loud knocking noise from a warm engine that occurs under load

• Pulley hub failure. Replace if necessary.
• The belt is too tight. Replace or adjust tension.
• The exhaust pipe touches the road surface. Secure the exhaust pipe.
• Crack in the flywheel.
• Increased clearance in main bearings. Replace if necessary. Increased clearance in connecting rod bearings. Replace if necessary.

A light knock from a warm engine

• Detonation. Check fuel quality. Check the ignition setting.
• Exhaust manifold leak. Tighten bolts and/or replace gasket.
• Increased clearances of connecting rod bearings. Replace bearings if necessary.

Knocking noises when starting the engine, lasting only a few minutes

• Oil of the wrong viscosity. Fill with oil of a viscosity that corresponds to the operating conditions.
• Increased axial clearance of the crankshaft. Replace the thrust bearing (half rings).
• Excessive clearance in main bearings. Replace worn parts.

Knocking noises on a warm engine at idle

• Poor belt tension or wear. Tighten and/or replace if necessary.
• Generator bearing. Replace if necessary.
• Gas distribution mechanism. Replace parts if necessary.
• The viscosity of the engine oil does not meet the requirements. Fill with oil with a viscosity corresponding to the season of vehicle operation,
• Too much clearance in the piston pin. Replace the piston pin and piston.
• Incorrect connecting rod adjustment. Check clearances and replace connecting rod if necessary.
• Insufficient clearance between cylinders and piston. Hone the cylinder and fit a new piston.
• The piston pin is offset from the axis in the other direction. Install the piston correctly.

The engine gets very hot

• Leakage in the engine cooling system. Check the expansion tank, hoses and radiator.
• The belt is slipping or damaged. Replace the belt if necessary.
• Thermostat stuck in closed position. Check and replace if necessary.
• Leaking cylinder head gasket. Check and correct if necessary.
• The electric radiator fan does not work.