The situation when the engine of the car stalls when gas is discharged or idling is familiar to many drivers. This is not just discomfort that makes you constantly gassing at traffic lights, but also a direct signal of a serious violation in the operation of the life support systems of the motor. If machineIgnoring the problem can cause the engine to suddenly stop in flow, creating an emergency situation on the road.
Instability of the power unit is most often caused by an imbalance between the amount of incoming air and the fuel supplied. The electronic control unit (ECU) tries to compensate for this imbalance by changing the angle of ignition advance and injection time, but the resources of regulation are not unlimited. As a result, you see floating turns, jitters when moving or a complete stop of the engine immediately after starting.
In this article, we will discuss in detail the mechanical and electronic causes of malfunction. We will consider both classic carburetor systems and modern injector engines with electronic throttle. Understanding the nature of the problem will help you save time on diagnosis in the service or even fix the breakdown yourself using a minimum set of tools.
Problems with air supply and sensors
One of the most common reasons why an engine stalls is a violation of the measurement of the amount of incoming air. Mass air flow sensor (MADR) transmits to the ECU indications, on the basis of which the duration of opening of nozzles is calculated. If the sensor is contaminated or malfunctioning, the mixture becomes either too poor, the engine stalls, or too rich, resulting in black smoke and loss of traction.
In addition, the condition of the throttle is critically important. In modern electronically controlled vehicles (E-Gas) the flap becomes engrossed with a load which prevents it from closing tightly or conversely jams the mechanism. Even a microscopic layer of oily dirt can change the throughput of the idling channel. Cleaning the throttle with a special aerosol often solves the problem without replacing expensive nodes.
Do not forget about the idling regulator (RX). This actuator is a stepping motor that physically opens the channel for air passage bypassing the closed throttle. If the RX rod is overgrown with a load or the engine winding is burned, the machine simply will not be able to maintain minimum speeds after releasing the accelerator pedal.
For accurate diagnosis of the state of the intake system, it is necessary to check the readings of the sensors through a diagnostic scanner. Errors in the memory of the ECU can indicate a specific node that requires attention.
⚠️ Attention: When cleaning the throttle on cars with electronic throttle control, an adaptation (training) procedure is often required through a diagnostic computer. Without this, the revolutions may remain high or the behavior of the gas pedal will become inadequate.
Unrecorded air suction
The tightness of the intake manifold is the foundation of stable engine operation. If excess air gets into the system past the DMRV, the fuel-air mixture becomes too poor. The engine begins to work unstablely, ignition gaps appear, and eventually the engine stalls. Finding the place of the sucker can be difficult, as cracks can be microscopic.
Most often, a leakage violation occurs in the following places:
- 🔹 Cracks in rubber pipes and crankcase ventilation hoses that dry out from time and temperature.
- 🔹 Damage to the nozzle or intake manifold sealing rings.
- 🔹 Depressurization of the gasket under the intake manifold, especially after engine overheating.
- 🔹 Failure of the valve of the crankcase gas recirculation system (PCV), which can jam in the open position.
To detect the sucker, professionals use a smoke generator. The device pumps smoke into the intake manifold with the engine shut down, and the leakage places become visible to the naked eye. In garage conditions, you can use the method of spraying suspicious places with a carburetor cleaner (for example, Carb Cleaner) on the running engine. If the revolutions change, then the liquid got into the cylinder through the crack, temporarily enriching the mixture.
Ignoring the air sucker leads not only to a stalled motor, but also to the burning of valves due to impoverishment of the mixture and an increase in the combustion temperature. This also leads to increased fuel consumption as the ECU tries to compensate for the poor mixture by increasing the injection time.
Use a long medical tube to listen to the hissing of air by ear in the intake manifold area. This is an old but effective method of finding large suctions.
Fuel system and mixture quality
If the air is in good shape, the problem may be fuel. The pressure in the fuel ramp must be strictly defined. If fuel-pump worn or clogged fuel filter, pressure drops, and the engine does not have enough strength to maintain idling, especially under load (air conditioning, steering).
A frequent cause is contamination of the nozzles themselves. The sprayer of the nozzle eventually becomes covered with resins, which worsens the spray torch. The fuel does not burn completely, the engine is trembling and may stall. Regular use of quality additives or ultrasonic cleaning of nozzles helps restore performance.
Also worth mentioning is the fuel pressure regulator (RDT). If its membrane is damaged, gasoline can directly enter the intake manifold through a vacuum hose, enriching the mixture, or the pressure in the ramp may not hold after the ignition is turned off, making it difficult to restart.
☑️ Diagnostics of the fuel system
Ignition system and electrician
An unstable spark is another factor that causes the car to not keep pace. If high-voltage wires, ignition coils or candles are worn out, ignition gaps occur. At idle speeds, this is especially noticeable: the engine begins to vibrate and stalls.
Particular attention should be paid to the state of candles. Load on the electrodes, an incorrect gap or failure of one of the elements lead to the fact that the cylinder stops working. In modern systems Common Rail or direct injection requirements for the quality of the spark is even higher.
Problems can also be found in the wiring. Oxidized contacts, worn harnesses or bad "mass" of the engine can work wonders: the machine works perfectly, then deafens for no apparent reason. Diagnostics of electricians require multimeter and circuitry of the electric equipment of a particular car.
Below is a table of symptoms and possible causes in the ignition system:
| Symptoms. | Possible cause | Method of verification |
|---|---|---|
| The engine is idling. | Coil or candle malfunction | Turning off the cylinders |
| Deafening under load | High-voltage wires break | Visual inspection in the dark |
| Hard launch and stall | Weak battery charge | Voltage measurement of the onboard network |
| Floating around chaotically | DPCV malfunction (crankshaft sensor) | Computer diagnostics |
⚠️ Attention: When replacing spark plugs on engines with an aluminum head of the cylinder block, strictly observe the tightening moment. The pull can lead to a break of the thread, and the underweight - to the burnout of the candle and damage to the head of the block.
Mechanical malfunctions of the engine
If all systems are working properly, but the machine continues to stall, the reason may be the mechanics. Compression in cylinders is the pressure that is created by the piston when the mixture is compressed. If the compression is low due to wear of piston rings, burn-out of valves or breakdown of the gasket of the GBC, the engine will not be able to operate steadily at low revs.
Gas distribution phases also play a key role. If the belt or GRM chain is stretched, or the labels are incorrectly displayed (even on one tooth), the valves will open at the wrong time. This leads to loss of power and unstable operation. On phase-rotor engines (VVT-i, VTEC, VANOS) failure of phase control solenoids also causes rotational rotations to float.
The opening of the EGR (exhaust gas recirculation) valve causes the exhaust gases to be continuously injected. At idling, this "strangles" the engine, since too much inert gas and little oxygen enter the cylinders.
How to check compression without a device?
There is a popular method of "hearing". Turn all the candles out except one. Insert a tight rubber cone into the candle hole or just press your finger (caution!). Scroll the starter. If the engine spits and creates a tangible pressure, the cylinder is probably alive. Only the compressometer will give accurate data.
Specifics of work on cold and hot engine
The behavior of the engine immediately after start-up and after warming up can be radically different. If the car stops only "cold", most often it is the fault coolant temperature sensor (TTP). If it transmits incorrect data that the engine has already warmed up, the ECU will not enrich the mixture and increase the speed necessary for stable operation of the cold engine.
When the problem manifests itself "hot", the heat expansion effect comes into play. Heated parts increase in size, gaps decrease. Can jam the idle regulator or the throttle position sensor (DPD). Also on the hot can manifest problems with the gas pump, which is overheated by hot fuel in the tank.
It is important to distinguish these conditions in the diagnosis. Write down at what temperature the engine fails. This will significantly narrow the search for the master.
Accurate diagnosis requires an analysis of the engine in different temperature regimes. The problem of "cold" and "hot" often has different roots.
Frequently Asked Questions (FAQ)
Why does the car stop when it brakes?
This is a classic symptom of a malfunction of the idling regulator (RXX) or air sucker. When braking the engine, the throttle is closed, and air must flow through the bypass channel. If the channel is contaminated or the RX does not work, the engine will die from lack of air.
Can a car die because of bad gasoline?
Yes, low octane or water in the fuel cause detonation and unstable combustion. The ECU tries to adjust the angle of ignition, but if the fuel is very bad, the engine may stall, especially under load or idling.
How do I know if the throttle position sensor has died?
The main signs: jerks during acceleration, floating idling turns, a caught-up Check Engine indicator. When diagnosing the scanner, the sensor readings should change smoothly from 0% to 100% when the pedal is pressed. Horse racing or "dead zones" indicate a malfunction.
Should I wash the injector myself?
Self-washing through the fuel ramp is possible, but requires caution and special equipment. Aggressive fluids can damage rubber seals or wash the protective film off the fuel pump. It is better to entrust this to professionals or use soft additives in the tank prophylactically.
What to do if the car stops and does not start?
Check for spark and pressure in the fuel ramp. If there is a spark and gasoline arrives, most likely the problem is compression or synchronization of sensors (DPKV, DPRV). In an emergency situation, you can try to blow the intake manifold with compressed air or check the safety locks of the gas pump.