Difficult start
The crankshaft turns, but the engine does not start for a long time. Eventually, the engine starts, or it may be that shortly after starting, the engine stalls.
Make a check:
- Fuel for the presence of water impurities.
- pressure in the fuel system.
- Throttle position sensor for sticking; The voltage of the sensor signal measured by the voltmeter must be below 1.25 V.
- Fuel pump relay. Connect a test lamp between pump relay circuit 120 and ground. The lamp should be on for 2 seconds after the ignition is turned on.
Check the fuel pump shut-off valve in the fuel tank. The valve ensures that fuel flows from the fuel line back to the tank after the engine is turned off. The following procedures are required for verification:
- Switch off the ignition.
- Disconnect the fuel line at the filter.
- Remove the fuel tank cap.
- Connect the pump used to test the radiator to the fuel line and pressurize to 103 kPa. If the pressure does not drop within 60 seconds, the check valve is good.
Check the ignition system for:
- Compliance of the output voltage of the ignition system with the norm using a control device.
- No wear on the distributor shaft.
- Absence of short circuits and violations of wire insulation.
- Idling air supply control system.
- Throttle shaft and linkage sticking. When stuck, the signal voltage from the throttle position sensor may be high (which indicates throttle opening), in connection with which, the control unit will not be able to control the operation of the engine at idle. Measure the sensor signal voltage. Closed throttle voltage should be below 1.2.
- Manifold absolute pressure sensor with engine off and ignition on. Compare the measured voltage value of the sensor signal with the voltage measured on the vehicle that was in good condition. The voltage deviation should be no more than 400 mV. For another test option: start the engine and, at idle, disconnect the connector of the manifold absolute pressure sensor. If engine performance improves, replace the sensor and recheck.
- Compressor or A/C relay.
- Refrigerant pressure in the air conditioning system. If the pressure is too high, check for excess refrigerant and for a fault in the pressure switch.
- Cooling fan.
- Compression in the cylinders.
- Battery wires. Wires must be free from contamination and securely fastened. Current leaks can cause the idle air control valve to change position and cause poor engine performance. The valve will not operate if the system voltage is below 9V or above 17.8V.
Check the CO content in the exhaust gases using an appropriate instrument. If the CO content is too low (below 0.3%), the air-fuel mixture is too lean, and the signal voltage of the CO potentiometer will be small (below 0.06 V). As a result, the ECM reduces the amount of fuel supplied to the engine, which leads to difficulties in vehicle handling.
Increased content of harmful substances in exhaust gases
Measurements give high concentrations of harmful substances; There may be a smell of rotten eggs. The appearance of an unpleasant odor is not necessarily a sign of improper combustion. Carry out a thorough inspection. Perform circuit diagnostics.
Check:
- No suction in vacuum lines.
- Cooling system and fan.
- Remove carbon deposits with engine cleaner.
Instructions for use are given on the packaging.
If high NOx concentrations are detected during measurements, check the reasons why the mixture is too lean or the combustion temperature is too high.
If high concentrations of hydrocarbons and CO are detected during measurements, or the exhaust has an unpleasant swing, check the reasons why the working mixture is too rich:
- Deviation of fuel pressure from the norm.
- Blockage or sticking of the valve of the positive crankcase ventilation system or blockage of the hose of the system.
- Incorrect installation of the fuel tank cap.
- Faulty spark plugs, spark plug wires, or ignition system components.
- Incorrect ignition timing.
Self-ignition in cylinders
The engine continues to run after the ignition is turned off, but very unevenly. If the engine is running, check the ignition switch and ignition control.
Check injector for leaks.
Connect a voltage of 12 V to the test terminal of the fuel pump to turn it on; pressurize the fuel system.
Inspect the injector and throttle body for fuel leaks.
Back flashes
Ignition of fuel in the intake manifold or in the exhaust system with a loud sound.
Check:
- The output voltage of the ignition coil.
- Ignition order, paying attention to the distributor cap, spark plug wires. their correct fit.
- Setting the ignition timing.
- Serviceability of spark plugs, candle wires and covers.
Check compression (detection of stuck or loose valves).
Check valve timing.
Check the operation of the valve levers.
Interruptions, failures, twitching
A short-term loss of engine sensitivity to pressing the gas pedal can occur at any speed. Usually most strongly manifested when trying to start moving after stopping. In severe cases, it can lead to engine shutdown.
Carry out a thorough inspection.
Check:
- Fuel pressure.
- Fuel for the presence of water.
- Throttle position sensor stuck.
- Setting the ignition timing.
- Generator output voltage. The alternator requires repair if the voltage is below 9V or above 16V.
- To break the line connecting to the mass of the ignition system.
Skip flashes
Constant jolts during engine operation, usually increasing with increasing engine load. The exhaust pipe constantly makes splashing sounds at idle or at low speeds.
Conduct a thorough inspection. If it is suspected that misfiring at idle and while driving is caused by a malfunction of the ignition system, perform the appropriate checks.
Determine the idle cylinder:
- Start the engine. Disconnect the idle air supply actuator. Using an appropriate tool, disconnect one spark plug wire at a time.
- Possible drop in speed when disconnecting the spark plug wire from each cylinder (about 50 rpm) with subsequent uneven operation of the engine and even a stop. Turn off the engine, connect the idle air supply actuator.
- If there is no drop in speed when the spark plug wire is disconnected from one or more cylinders, or there is no significant difference in the degree of drop in speed, then the suspect cylinder (cylinders) check for spark discharges with an appropriate device. If there is a discharge, then unscrew the spark plug from this cylinder and check for the presence of: cracks, wear, incorrect clearance, burning of the electrodes, significant deposits.
Check spark plug resistance (resistance must not exceed 30,000 ohms).
If the previous checks have failed, perform the following checks:
- Inspection of the ignition system for moisture, dust, cracks, burns, etc. Spray spark plug passages with water mist to check for short circuits.
- Fuel system check (clogged fuel filter, presence of water in fuel, low pressure).
- Compression check.
- Checking the installation of valve timing.
- Remove the valve rocker covers, check for bent tappets. worn rocker arms, broken or deformed valve springs, worn cams. Make repairs if necessary.
Poor fuel efficiency
Fuel economy, measured in real road test conditions, is significantly lower than expected. In addition, fuel efficiency is significantly lower compared to that. that this car had before in the same conditions.
Check:
- Thermostat for valve failure (permanently open) or deviation from the specified temperature range.
- Fuel pressure.
Familiarize yourself with the owner's driving style.
Make a check:
- Vacuum hoses for cracks, kinks and loose fittings.
- Tire pressure.
- Masses of transported goods (overload loops).
- Applications when driving with too large or frequent accelerations.
Perform circuit diagnostics.
Check the air filter for dirt.
Check speedometer calibration.
Check spark plug wires for cracks, hardening, correct connection.
Check ignition timing.
Unscrew the spark plugs, check for dirt and cracks, wear, changes in gap, burnt electrodes and significant deposits. Replace if necessary.
Check compression.
Check the operation of the torque converter clutch.
Check brakes for sticking.
Re-check the fuel consumption with the fuel tank full.
Check for deposits in the exhaust system.
Irregular operation and engine stops at idle
The engine runs unevenly at idle. In more serious cases, the vehicle may vibrate. It is also possible to change the speed (fluctuations). This does not prevent the engine from stopping. Deviation from normal speed is possible.
Check:
- Setting the ignition timing.
- Mode switch circuit "Parking", "Neutral".
- Leak injector.
- Correspondence of the resistance of the sensor coil and contacts to the norm.
- No loose ignition coil connections.
- No moisture under the distributor cap.
- No dirt or cracks in spark plugs, no wear, no gap changes. burning of electrodes and significant deposits.
Speed fluctuations and (or) pops in muffler
Fluctuations in engine power at a constant degree of throttle opening at idle or while driving. It is subjectively felt as acceleration and deceleration of the car without a change in the position of the gas pedal.
Check:
- Setting the ignition timing.
- Fuel filter on the fuel line for dirt and deposits.
- Fuel pressure.
- Generator output voltage. Repair is needed if the voltage is below 9V or above 16V.
- The operation of the torque converter clutch (if available).
Check the CO content in the exhaust gases using a suitable instrument. If the CO content is too low (below 0.3%), the air-fuel mixture is too lean, resulting in a small signal voltage of the CO potentiometer (below 0.06 V). As a result, the ECM reduces the amount of fuel supplied to the engine, which leads to difficulties in vehicle handling.
Unscrew the spark plugs. Check for dirt and cracks, wear, gap changes, electrode burning and significant deposits. Also check the condition of the entire ignition system.
Loss of power, engine inertia, poor response to pressing the gas pedal
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.
Compare the behavior of the tested vehicle with the behavior of a similar vehicle. Make sure the complaint is justified.
Remove the air cleaner and check the degree of contamination of the air filter. Replace if necessary.
Check:
- Setting the ignition timing.
- Contaminants in the fuel filter, contaminants in the fuel and abnormal fuel pressure.
- The state of the lines connecting the control unit to the engine ground.
Check the exhaust system for obstructions:
- With the engine running and operating at normal temperature, connect a vacuum gauge gauge to any suitable vacuum port in the intake manifold.
- At a speed of 1,000 rpm, measure the vacuum.
- Slowly increase the speed to 2500 rpm. Measure the vacuum at a stable speed level of 2500 rpm.
- If the vacuum level at 2500 rpm drops by more than 21 kPa against the value measured at 1000 rpm. the exhaust system should be checked for interference.
- Disconnect the exhaust pipe from the engine and carry out the procedures indicated in the previous paragraphs. If the vacuum still drops more than 21 kPa, check the valve setting.
Check generator output voltage. The alternator requires repair if the voltage is below 9V or above 16V.
Check engine valve setting and compression.
Check the camshaft for wear.
Check the operation of the torque converter (if there).
Check the ignition voltage with a suitable device.
Detonation in the engine
Knocking, intensity from moderate to large. usually increasing with acceleration. Sharp metallic sound that changes when the throttle is opened.
Check if there is overheating.
- Low coolant level.
- Loose coolant pump belt.
- Restricted air or coolant flow through radiator.
- Faulty or incorrectly adjusted thermostat.
- Broken electric fan circuit.
- Changing the sensitivity of the coolant temperature sensor.
Check:
- Fuel quality, its octane number.
- The correct selection of spark plugs according to the thermal regime.
- Setting the ignition timing.
- Fuel system pressure (is there a fall).
- fuel system.
- Correct adjustment of the gearshift system.
- The operation of the torque converter clutch (if there).
- The correct selection of engine parts, such as the camshaft. heads, pistons, etc.
- Oil supply to the combustion chamber (is there an excess).
Remove carbon deposits with engine cleaner. Instructions for use are given on the packaging.
Increased oil consumption
Increased oil consumption can be caused by one of the following reasons.
Leakage of the lubrication system. Tighten screw connections and/or replace, if necessary, gaskets and seals.
Incorrect oil level readings with the dipstick. When checking the oil level, park the vehicle on a level surface and allow sufficient time for the oil to drain into the sump.
Too low idle speed. If the engine idle speed is not controlled by the electronic unit, adjust the idle speed as required and.
The type of installed pressure sensor does not match. Faulty pressure sensor.
Incorrect type of pressure gauge installed. Faulty manometer. Replace pressure gauge.
Incorrect oil viscosity or diluted oil. Top up with season-specific oil, or replace oil that is diluted due to moisture or unburned fuel mixture.
Worn or dirty oil pump. Replace oil pump.
Dirty oil filter. Replace oil filter.
Unscrewed or clogged mesh filter on the oil pump intake pipe. Clean and/or wash the strainer.
The side hole in the oil pump intake pipe is clogged. Replace tube.
Oil viscosity out of specification. Use SAE rated oil for appropriate operating temperatures.
Driving at high speeds or towing a trailer for long periods of time usually results in increased oil consumption.
Malfunction in the forced crankcase ventilation system.
Worn slinger caps and/or valve guides or missing slinger valves. Rebore guide bushings and install larger valves and/or new valve stem seals.
Poorly lapped, worn or broken piston rings. Let the new piston rings rub in for a while. If necessary, replace broken or worn piston rings.
Incorrect piston installation or incorrect size.
Low oil pressure
Low oil pressure can be caused by the following reasons:
- Excess bearing clearance. Replace bearing. if necessary.
- Cracks, pores, million plugs in the channels of the cylinder block. Repair or replace the unit.
- Missing or incorrectly installed lubrication plugs. Install plugs or replace if necessary.
Noise in the gas distribution mechanism
Noise in the gas distribution mechanism can be caused by any of the following reasons:
- Low oil pressure. Remove the cause.
- Loose valve levers. Check and repair if necessary.
- Worn lever and/or valve lifter.
- Breakage of valve springs, jamming of valves.
- Worn, dirty or defective valve lifters. Remove dirt, check and replace if necessary.
- Worn or defective timing shaft. Replace shaft.
- Worn valve guides.
Knocking in a cold engine that lasts two to three minutes and/or gets worse with increasing load
The flywheel touches the casing. Adjust the cover setting.
Unscrewed or broken balancer or drive pulley.
Increased clearance between pistons and cylinders Bore the cylinder and honing to size. Replace piston. The knock of pistons on a cold engine usually disappears after lapping. The knock of the pistons of a cold engine, which disappears after 1.5 minutes, is acceptable. Bent rod.
Strong knocking of a warm engine that occurs under load
Breakage of balancer or pulley hub. Replace if necessary.
Loosening automatic transmission bolts.
Accessory drive belts too tight. Replace or adjust tension.
The exhaust pipe touches the road surface. Attach the exhaust pipe.
Crack in the flywheel.
Increased clearance in main bearings. Replace if necessary.
Increased clearance in connecting rod bearings. Replace if necessary.
Slight warm engine noise
Detonation. Check fuel quality.
Also check the ignition installation.
Loosening automatic transmission bolts.
Exhaust manifold leakage. Tighten bolts and/or replace gasket.
Increased clearances of connecting rod bearings. Replace bearings if necessary.
Knocking when starting the engine, lasting only a few minutes
Oil of the wrong viscosity. Fill with oil. the viscosity of which corresponds to the operating conditions. When the engine is not running, some valves will be in the open position. Spring pressure on the hydraulic valve clearance adjustment mechanism will bleed off the hydrostatic pressure. Repair is required only when the problem persists.
Increased axial clearance of the crankshaft - replace the thrust bearing.
Excessive clearance in the front main bearing. Replace worn parts.
Knocking on a warm engine at idle
Poor tension or worn drive belts. Tighten and/or replace if necessary.
A/C compressor or generator bearing. Replace if necessary.
Gas distribution mechanism. Replace parts if necessary.
The viscosity of the engine oil does not meet the requirements. Fill in oil with a viscosity corresponding to the season of operation of the car.
Piston pin clearance too large. Replace piston pin and piston.
Crank adjustment. Check clearances and replace connecting rod if necessary.
Insufficient clearance between cylinder and piston. Honed the cylinder and fit a new piston.
The counterweight of the crankshaft has unscrewed. Tighten and/or replace worn parts.
The piston pin is offset from the axis to the other side. Install the piston correctly.
The engine gets very hot
Leaks in the engine cooling system, leaks in the transmission oil cooling system. Check for leaks and, if any, repair. Check expansion tank, hose and radiator filler cap.
The drive belt is slipping or damaged. Replace belt or tensioner if necessary.
Thermostat stuck in closed position. Check and replace if necessary.
Electric fan operation.
Leaking through the cylinder head gasket. Check and repair if necessary.
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