The situation when the engine suddenly stops at traffic lights or when gas is discharged is familiar to many drivers. This is not just an irritant that creates discomfort when maneuvering in a dense flow, but also a direct signal of a serious violation in the work. fuel-supply or ignition. If the car stops idling, it means that the electronics or mechanics cannot ensure stable combustion of the fuel-air mixture with minimal load on the shaft.
Ignoring this problem often leads to the fact that the car begins to stall even in motion when changing gears or braking, which creates an emergency situation on the road. In most cases, idle-stage This is due to the imbalance between the amount of incoming air and fuel supplied. The computer tries to compensate for the imbalance by changing the angle of ignition advance or the position of the throttle valve, but if the regulators' resource is exhausted or there is a mechanical malfunction, the revolutions fall to zero.
Diagnostics of such a malfunction requires a consistent approach, since there can be many reasons: from banal pollution to the failure of expensive sensors. Modern injection engines They are extremely sensitive to the purity of air channels and the condition of electrical contacts, so the search for a cause often begins with a visual inspection and computer diagnostics.
The main reasons for the unstable operation of the engine at idling
The fundamental reason for the car deafness on singles lies in the violation of the proportion of the mixture. The internal combustion engine can only work when the ratio of gasoline to air is in a strictly defined range. If too much air (poor mixture) or not enough (rich mixture) enters the cylinders, ignition becomes impossible at low crankshaft revs.
The most common culprit is becoming suction. This occurs when cracks appear in the intake system, through which atmospheric air is drawn into the collector, bypassing the mass air flow sensor (MMRV). The electronic control unit (ECU) does not βseeβ this additional volume and delivers a standard amount of fuel, as a result, the mixture is diluted, and the engine stalls.
The second common group of problems are malfunctions in the throttle control system. In modern cars with electronic throttle (E-Gas), the valve is controlled by an electric motor according to ECU signals. If the mechanism jams or the throttle position sensor (TRP) transmits incorrect data, the computer cannot properly open the channel to maintain the revs.
β οΈ Note: If the car stalls immediately after launch and no longer starts, do not try to spin the starter indefinitely. This can fill the spark plugs or drain the battery. Check for spark and pressure in the fuel ramp.
The impact of fuel quality should also be considered. Low octane number or the presence of water in gasoline can cause detonation and ignition skips, which is especially noticeable at idle, when the spark energy is minimal. Unstable pressure In the fuel ramp, caused by a dying gas pump or a clogged filter, also leads to a drop in revolutions.
Failures in air supply and sensor systems
The air intake system is the "light" of the engine, and any failure in its operation instantly affects the stability of the engine. The key element here is idler Or the idle control valve. This stepper motor, which mechanically opens the channel bypassing the closed throttle, ensuring the start and operation of the engine without pressing the gas pedal.
Over time, oily soak from crankcase gases accumulates on the rod of the RXX and in the channels of the throttle node. This coar narrows the passage section of the channel, and the valve simply does not have enough stroke to let the right amount of air through. As a result, the speed drops, and the engine stalls. Cleaning the knot often solves the problem, but if the stepper motor has exhausted its life, it will have to be replaced.
The mass air flow sensor (MMRV) plays a critical role in the formation of the mixture. If his readings are incorrect due to contamination of the filament or failure, the ECU will prepare the mixture with the wrong composition. Dirty DMRV often shows less air flow than it actually is, which leads to the re-enrichment of the mixture and the resulting flounder.
- π Check the integrity of the air filter corrugated β any crack after the sensor creates a suction.
- π¨ Purging the idle channel with a carburetor cleaner can temporarily restore the valve.
- π Disabling the DMRV on the go (for inspection) sometimes helps to identify its malfunction if the nature of the engine changes.
Particular attention should be paid to the crankcase gas ventilation (PCV). If the PCV valve jams in the open position, an excess amount of crankcase gases enter the intake manifold, which also violates the composition of the mixture. In some models of cars, for example, with TSI engines or EcoboostThe PCV valve membrane can break, creating a huge air suction, causing the machine to stall.
Problems with fuel system and ignition
If the air is all right, the problem may lie in the supply of fuel or the moment of spark formation. For stable idling, a certain pressure in the fuel ramp is required. If fuel-pump intermittently works (interrupted) or the fine filter is clogged with dirt, the pressure drops, and the injectors cannot spray the desired dose of gasoline.
The nozzles also need attention. Over time, they can coke and the spray torch becomes incorrect. Drops of fuel do not have time to evaporate and settle on the walls of the intake manifold, not getting into the cylinder at the right time. This is especially true for direct injection engines where the requirements for spray quality are extremely high.
In the ignition system, candles often become the cause of deafness. If the gap on the electrodes is too large or the soda prevents the formation of a spark, at low revs (when the voltage in the onboard network is minimal) breakdown does not occur. Ignition skips In one or more cylinders, the engine starts to triple and stall.
β οΈ Note: When replacing spark plugs, be sure to check the gap and the kalyl number. Installation of candles with an inappropriate potassium number can lead to kalyl ignition and destruction of the piston group.
Ignition coils and high-voltage wires can also break through the mass, especially in wet weather. Microcracks in the insulation of the coil allow current to go to the engine body, bypassing the candle. Diagnostics of this node often require replacement of elements alternately to identify defective.
How to check the pressure of fuel without a pressure gauge?
You can squeeze the reverse hose of the fuel ramp on the working engine (if the design allows). If the revs start to rise, the pump is working, but the pressure in the system was low due to leaks or a regulator. However, this method is rough and does not give exact figures.
Effects of temperature sensors and ECUs
The electronic engine control unit makes decisions based on the readings of many sensors. One of the most important is coolant temperature sensor (TTP). If it is faulty and shows the ECU that the engine is already warmed up (although it is actually cold), the computer will not enrich the mixture and boost its speed to warm up. As a result, the cold engine will stop immediately after start-up.
Conversely, if the sensor shows a strong frost with a warmed-up engine, the mixture will be overenriched, which will lead to black soak on candles and unstable operation. Errors in the readings of the CTD are often not displayed on the dashboard as a οΏ½οΏ½Check Engineβ, since the sensor is formally serviceable, but lies in the readings.
Also worth mentioning is the lambda probe (oxygen sensor). Although it comes into operation after warming up, its incorrect data can knock down the algorithms for correcting fuel supply in long-line memory. If lambda probe βlazyβ or has an incorrect characteristic, the ECU may incorrectly adjust the mixture at idle.
| Symptoms. | Probable cause | Method of verification |
|---|---|---|
| He's cold on the ground. | RX, air suction. | Diagnosis by scanner, temperature check |
| He's gonna die hot. | DMRV, gas pump overheating, DPDV | Fuel pressure measurement, DMRV check |
| Floating speed | Air pump, RX, EGR | Smoke machine suction, throttle cleaning |
| Deafness when braking | Vacuum amplifier, automatic transmission | Checking vacuum hoses, diagnostics of the box |
Diagnosis: Finding air sucker and errors
The search for malfunctions should begin with computer diagnostics. Even if the light bulb Check Engine does not burn, in the memory of the ECU can be stored pending errors (waiting for confirmation) or the values of fuel supply corrections. High air correction values (e.g. +15% and above) directly indicate that the computer is trying to compensate for the poor mixture, which is typical for a sucker.
To search for air suckers, professionals use a smoke machine. Smoke is fed into the intake manifold with the engine silenced, and the smoke exit points become visible to the naked eye. At home, you can use the method of spraying the connections with a carburetor cleaner or brake fluid on the working engine. If the revolutions change when liquid hits a specific joint, then there is leakiness.
It is important to check the condition of the intake manifold gaskets. On used engines, rubber seals bluff and crack, letting air through. It is also worth examining the sealing rings of nozzles. In old cars with a carburetor or mono-injection, the causes can be purely mechanical: wear of the diaphragm, needle jagging.
βοΈ Checklist of primary diagnostics
Remediation and prevention
Resolving the problem depends on the cause found. If it is a matter of pollution, quality will help. throttle-washing and the idle regulator. It is important to use special cleaners that do not damage the rubber seals and molybdenum coating (if any) on the damper. After cleaning, many cars require a procedure to adapt the throttle through a diagnostic scanner or special manipulation of the pedals.
If an air suction is detected, damaged pipes or gaskets should be replaced. The use of a sealant in the intake system is allowed only in extreme cases and only a special heat-resistant type designed to contact gasoline and oil. Normal silicone will quickly collapse.
Prevention of such problems includes regular replacement of the air filter, use of quality fuel and periodic cleaning of the injector. It is also recommended to check the condition of candles and coils every 60-80 thousand kilometers, without waiting for their complete failure.
β οΈ Note: After cleaning the throttle on some cars (for example, Nissan, BMW, VAG) be sure to do a reset adaptation. Without this, the revolutions may remain high or the behavior of the gas pedal will become inadequate.
Use only a quality carburetor cleaner marked "Safe for sensors" (safe for sensors) to avoid damaging the sensitive elements of the DMRV or the coating of the valve.
90% of idling problems are solved by cleaning the throttle, replacing candles or eliminating air suction. Donβt be in a hurry to change expensive sensors without carefully checking for simple reasons.
Frequently Asked Questions (FAQ)
Why does the car stop on blanks when it is warmed up?
This often indicates a malfunction of the throttle position sensor (DPD) or lambda probe. It is also possible that when heated, parts expand and the gap in the place of the air sucker increases, or the gas pump overheats and productivity drops.
Could low oil levels be the cause of deafness?
There is no direct connection, but if the oil emergency pressure sensor works, the ECU can emergency shut down the engine to protect against liner turns. Also, at a critically low level of oil, air can be sucked through the crankcase ventilation system.
How to distinguish a generator from other causes?
If the car stalls because of the generator, then before that the battery lamp usually lights up, the headlights dim, and the engine works unevenly due to the lack of voltage on the ignition coils. Check the voltage at the battery terminals with the engine running - it should be 13.5-14.5 Volts.
Why does the automatic transmission machine stop when switching to D or R?
When switching gear, the load on the engine increases sharply. If the idle regulator is dirty or there is an air sucker, the engine does not have time to add revolutions to compensate for the load and stalls. Also, the cause may be a faulty sensor of the position of the brake pedal.