Air leaking through the throttle valve, what to do? Methods for determining air leakage Air leakage VAZ 2115 injector symptoms.

Any engine internal combustion must work on a mixture of air and fuel, which are tightly regulated by electronics, if it is an injection engine, or mechanics, if it is a carburetor engine. Any imbalance in the proportion of air and fuel leads to incorrect engine operation, a drop in power, and an increase in fuel consumption. Intake manifold air leaks can severely affect engine stability. How to check and determine the malfunction, identify the main symptoms of suction, let's figure it out right now.

Manifold Air Leakage Symptoms: Check and Identify

Clear signs of a cracked hose

Any unauthorized penetration of excess air into the power system leads to a depletion of the working mixture. The optimal balance of fuel and air is violated, as a result of which the engine pounds, idle speed can disappear altogether, while at speeds above 2-3 thousand the engine can work quite tolerably.

Error P0300

In addition, the electronic engine control unit can show a number of errors - P0171, lean mixture, an error may appear P300, talking about misfire in the combustion chamber. Several other errors may occur depending on the engine model.

Nevertheless, the main symptoms of air leakage in the intake manifold are:

• unstable idle speed, the engine shakes, it is impossible to adjust idle;
• the engine may stall in transient modes of operation;
• dips during acceleration;
• high fuel consumption;
• difficult start at any air temperature;
• drop in power, especially at speeds below 2-3 thousand;
• the engine is troit, one or more cylinders do not work in certain modes.

Where can the air be sucked in?

One of these symptoms is enough to talk about air leakage in the intake tract. It can be quite difficult to pinpoint the exact location of the air intake, since the place of attachment and sealing of the intake manifold to the cylinder head is far from the only way to suck in excess oxygen.

Depending on the engine model, there may be several places of suction:

1. Damage or burnout of the gasket the intake manifold is one of the most common places for leaks.

   New intake manifold gaskets

2. Seals for injectors in injection motors.
3. Backlash and leaks in the axles of the throttle valves of carburetor engines.
4. Vacuum brake booster.
5. Connections and hoses that are fixed to the manifold.

   A leaky hose on the manifold caused an air leak

6. Throttle gaskets in injection motors.
7. Valves of the adsorber, plugs on the manifold, leaks in the sensors.
8. Idle controllers of questionable quality may be leaking.

   Leaky idle speed control

9. Bushings.

As you can see, troubles can be expected not only from the gasket of the collector or the collector itself, at the same time there are a number of measures that will help to find the place of breakdown and quickly eliminate the malfunction.

Determine the place of air leak

The most effective way to determine the location of an air leak is visual.

True, for this you have to either find or assemble the simplest smoke generator. Smoke launched into the intake system will instantly show the place of suction with high accuracy. It is clear that not even every service station has a smoke generator, so the simplest device can be assembled by hand.

Do-it-yourself smoke generator

For this, a blowing air gun, a compressor with a receiver and a pack of cigarettes for smoke will come in handy. The pistol is simply connected to an air receiver or compressor, a cigarette is inserted into the nozzle of the pistol, a pressure of about 0.5-0.8 atm is injected, and the smoke under pressure enters the intake manifold.

Homemade smoke generator

The flaw will become noticeable as soon as the smoke finds a place to exit.

Another way to find the place of "suction"

The second method for determining the location of the suction is more time consuming and time consuming. For this it will come in handy flammable liquid(ether, gasoline with a high octane number, liquid for quick start of the engine in a can). To check and determine the place of suction, it is enough to start the engine and spray liquid on the manifold interfaces.

Sometimes the suction is clearly audible by the characteristic whistle or hiss, but this does not happen in all cases. Therefore, it is necessary to methodically spray with liquid the place where the intake manifold meets the block head and all the suspicious connections that we have listed above. As soon as the liquid enters the place of breakdown, it will be sucked into the intake tract and the engine speed will sharply increase for a while.

other methods

There are several more methods for detecting suction. They consist in the accurate measurement of the vacuum in the section from the throttle valve to the combustion chambers, however, the equipment used to implement this method is not always available, and the accuracy of localizing the place of depressurization using this method is minimal.

conclusions

The optimal methods for diagnosing air leaks in the intake manifold on their own are the use of smoke and spraying the manifold, corrugations, throttles with a thin stream of flammable liquid. Successful diagnostics and smooth roads to everyone!

If, when you press the gas pedal suddenly, your car engine starts to choke or stalls, in many cases this is a sign of a clear air leak. Excessive air is being supplied to the power unit, which results in a too lean air / fuel mixture. And it does not burn as well as the manufacturer intended. This leads to triplet engine and unstable idling.

The main signs of air leaks

Most often, air leaks from a car engine are manifested by the following symptoms:

• Problems with starting after a long stay (for example, in the morning).
• Decrease in power. On power units with an air flow meter, idle speed falls, and on engines with an absolute pressure sensor (MAP sensor), the speed, on the contrary, increases (diagnostic, misfire and lean mixture also appear).
• Unstable operation at idle - the tachometer needle constantly twitches, and at the "bottom" the engine may stall. In cars with a carburetor engine, the quantity and quality of the mixture is practically impossible to adjust, since the air is supplied in an excess volume.
• Increased fuel consumption - to start and continue driving, the driver is forced to maintain high revs without switching to higher speeds.

Typical air leaks

Of course, each case is individual, but suction usually occurs in such places of the engine:

• throttle assembly gasket;
• connection of the intake manifold with the cylinder head;
• vacuum brake booster;
• adsorber valve;
• a branch pipe connecting the throttle assembly and the air filter housing;
• vacuum hoses, their joints and tees;
• sealing gum for fuel injectors;
• idle speed regulator.

In the case of cars equipped with carburetor motors, it is much easier to find the suction. There are not a lot of electronic devices and sensors, and the additional air usually enters the engine through a vacuum brake booster or one of the elements of the carburetor itself.

Air leaks in the carburetor:

• gasket (suction is easy to detect by the presence of soot);
• choke axles;
• mixture quality adjustment screw;
• a leaky throttle valve connection;
• Damage to economizer diaphragm, throttle damper vacuum diaphragm, or starter diaphragm.

Diesel fuel system air leaks

Typically, the airing of the diesel engine fuel system is caused by damage to the joints of the pipes connecting fuel tank and filter or filter and high pressure fuel pump.

Air leaks in the damaged fuel system are due to the fact that the pressure when supplying diesel fuel from the tank is below atmospheric. Therefore, it is extremely difficult to identify the place of suction.

On the diesel cars, which have been produced in recent years, the penetration of air into the fuel system occurs more often compared to older diesel engines. The reason lies in the different design of the hoses, the service life of which has been significantly reduced. Previously, these elements were made of brass, and now they are made of plastic. Constant vibrations cause wear on the plastic and rubber seals. Most often, owners of cars with a mileage of about 150-200 thousand kilometers encounter such difficulties, and often the suction manifests itself in winter.

The most popular reasons for suction in such cases:

• wear of clamps and hoses;
• damage to the fuel filter seal;
• damage to the seals on the fuel pump cover or drive shaft;
• leaking fuel lines;
• damage to the return fuel line;

Important! Usually the problem is caused by worn out sealing elements. Airing of the fuel supply system can occur on the supply or return line.

Signs of air leakage on a diesel car

Most often, the engine does not want to start after long periods of inactivity. The driver is forced to turn the key in the ignition lock repeatedly using the starter. This is accompanied by the appearance of smoke from the exhaust pipe, which is a sign of normal fuel supply. If the suction is very significant, the engine will not only start poorly in the morning, but also stall while driving.

The reason lies in the fact that the pump cannot operate normally at idle speed, because too much air enters the chamber. At high speeds, the high-speed fuel pump even more or less copes. Such symptoms are not always caused precisely by suction, so we advise you to check the "diagnosis" by installing transparent fuel pipes.

How to find air leaks in the diesel engine fuel system

Air can enter the system through the connection, fuel tank, or tubing. The search is done quite simply - by applying pressure or by elimination. In the first case, it is necessary to apply pressure to the fuel tank, after which you will hear a characteristic hiss at the place of suction, or you will see drops of fuel. The second method is to check the elements of the fuel system one by one, ensuring that fuel is supplied from the tank, not the tank. First, we connect to the fuel pump and move on.

Intake manifold air leaks

If air enters the engine that the air flow meter or MAP sensor cannot “see”, a too lean mixture of fuel and air will form. This problem is caused by air leaks in the intake tract.

Main reasons:

• overheating of the motor (affects the condition of the gaskets);
• external interference;
• damage to gaskets as a result of improper use of the carbcliner.

Very often, difficulties can arise if the seal between the intake manifold and the cylinder head is damaged, since it is not easy to visually detect such a leak.

Finding a choke in the manifold

On gasoline engines, excess air may end up in the manifold due to depressurization of the air ducts, wear of the sealing rubber of the fuel injectors, or damage to the hoses leading to the vacuum brake booster.

In order to find air leaks, different methods are used:

1. Shut off the air supply. It is necessary to disconnect the pipe from the filter housing and start the engine. After that, cover the branch pipe with your hand - if there is no suction, the engine will stall. If the engine continues to run and you hear hiss, there is definitely a suction.
2. Pinching the hoses. It is necessary to start the engine and after a certain time try to hear hiss. If it was not possible to find the place of damage to the tightness, it is necessary in turn to pinch the hoses that are connected to the receiver. If you pinch and release the hose and it affects performance power unit, look for a problem in this zone.
3. Compressed air. The intake system of the idle engine must be treated with soapy water, then shut off the air supply from the filter and pump air through one of the pipes.
4. Spraying with a combustible mixture. To find the place where air is leaking into the engine, such means as gasoline, WD-40 or a carburetor cleaner are used. With the help of the selected product, it is necessary to spray all the joints. When the fluid is in the place of suction, you will notice changes in the engine's operation (rpm should rise or fall). It is better to use a medical syringe for spraying.

Using this method, check the following places: the pipe between the valve cover and the idle speed regulator, the pipe between the MAF sensor and the IAC, the intake manifold and throttle body connection, the manifold and cylinder head connection, injector seals, all hoses in the clamping areas.

1. Smoke generator. Not all motorists have such a device, and therefore it is usually used in car repair shops. You can buy a ready-made solution or make it yourself (there are enough instructions and videos on the Internet). The bottom line is that you need to ensure the supply of smoke through any hose to the intake manifold. Smoke will seep in problem areas.

Reading 6 min.

For a car to drive well, it must be well looked after. DPDZ is a device in a car that changes the angular position of the throttle valve. But do the same if your car has air leaks through the throttle column.

The throttle position sensor is used to detect the speed and degree of opening of the throttle valve. The throttle position sensor, or as it is abbreviated as TPS, is a device that was originally designed to convert the angular position of the throttle valve into a DC voltage. This sensor is considered one of the sensors in all electronic engine management systems of a fuel injection vehicle. After receiving a signal from the throttle position sensor, the controller monitors the angle by which the throttle valve is deflected. Based on the information received from the throttle sensor, the electronic control unit selects the fuel transfer mode.

In this article, we will try to answer the following frequently asked questions:

• Air leaks through the so-called throttle valve;
• Throttle valve malfunction signs;
• How to remove oil in the throttle valve?;
• What to do if after cleaning the throttle body the revs have risen?
• Cleaning and adjusting the throttle valve.

Throttle valve malfunctions and methods of their elimination

Before discussing the diagnosis and symptoms of a throttle position sensor, let's talk about the significance of the sensor. The throttle position sensor plays a huge role in the control of the car's engine, because thanks to its readings, the control unit calculates the fuel proportions, as well as corrects the ignition timing. In the event of a breakdown of this sensor, the driver is immediately notified of the error via the control unit. An error notification appears on the dashboard, namely, you will see a light bulb - “Chek”. Please note that the error that occurs only indicates a malfunction in the throttle position sensor circuit, but cannot localize it. That is, if the sensor settings are violated, the unit will not be able to recognize the error.

To eliminate a breakdown, each driver needs to know the elementary signs of a malfunction. Many drivers, when faced with such a problem, decide to clean or replace the throttle valve, but after that the revs may rise. In order to return the previous rpm, you need to adjust the throttle, and we will tell you exactly how to do this a little later.

The electrical engine management system detects failures related to wire breaks or short circuits. There may be some signs of malfunction in the ignition and power supply system. Also, due to a breakdown, air leaks through the so-called throttle valve may occur or the speed may rise. Turnovers have certain outward signs, but the error codes are not marked in the memory of the electrical unit. Consider the main signs of breakdowns:

• Slight difficulty in starting the engine;
• Dips or jerks are felt during the operation of the engine;
• Small enough power;
• Frequent occurrence of detonation;
• Failing, holding and twitching;
• Engine operation with slight interruptions;
• Increased fuel consumption;
• A specific gasoline smell arises in the exhaust system during gasoline processing;
• Instability during the operation of the engine, and during operation on a cold run it stops;
• Sometimes the fuel mixture ignites spontaneously;
• Some pops are heard in the intake manifold or muffler.

If you find any of the above malfunctions, but the self-diagnosis system does not determine the breakdown code from the throttle position sensor, you do not need to jump to conclusions and change it. In this case, the malfunctions you find may be caused by completely different reasons.

Now let's talk about how to diagnose air leaks through the throttle. Before correcting the reasons for the air leak, familiarize yourself with the consequences. Naturally, after avoiding problems with air leaks, unpleasant consequences may arise, namely, the speed will increase. In order to determine if air is leaking at all and its reasons, check the following places:

• Throttle valve and its axis;
• Cold start nozzle;
• Corrugation behind the throttle position sensor;
• The inlet of the crankcase cleaner located on the corrugation;
• Throttle body and corrugation connection;
• Nozzle rings;
• Conclusions through which gasoline vapors escape;
• The tube of the vacuum brake booster.

How to check the places where air leaks can occur?

• Use diesel fuel to spill the nozzles;
• Disconnect the mass air flow sensor from the air filter housing and cover it with your hand. After that, the corrugation should shrink a little and, at best, due to the fact that the air suction has stopped, the engine will stall;
• Disconnect everything except the throttle valve and close it with your hand. After that, due to the fact that the air suction has stopped, the engine should also stall;
• Spray places where air is leaking with a carbcliner.

Cleaning and adjusting the throttle valve

We figured out how to diagnose air leakage and now we will discuss the consequences that may arise. Once there, and more often than not, air is leaking, I cleaned the throttle valve, but after that the revs rose. And this is a fairly popular problem! Quite often, drivers have the following question: I cleaned the throttle valve, and after that the revs increased greatly. What to do?.

So, after you have a question like “I cleaned it up, what should I do next? My turnovers have risen! " don't worry. The reason your turnover went up is most likely due to improper regulation. Checking and regulation must be started by turning on the ignition. If the light does not light up, then go directly to the throttle position sensor itself. Here, using a multimeter, it is necessary to check the minus. Pierce the wires one by one and look for mass, but do not turn on the ignition. In the same way, you can make sure that the power supply chain is in good working order; for this, pierce the wiring one by one. Then we move on to performing the following basic tasks:

• Make sure the idle contacts open;
• Check the condition of the tracks that carry current and the film resistor.

On the throttle position sensor connector, find the idle contact and place the multimeter probe on it, and then move it. If the sensor is correctly adjusted while driving, the voltage will immediately begin to change from zero to the supply voltage. The coating of the variable film resistor has a strong influence on the smooth functioning of the throttle position sensor, and this is very important for the correct perception of the data by the engine control unit. Place the dipstick on the last wiring and slowly move the throttle. After that, the voltage should rise slowly without any jumps or dips.

Regulation algorithm:

• Remove the corrugated tube and check the condition of the throttle valve;
• Using a cotton wool soaked in gasoline, wipe the intake manifold and flap;
• Unscrew the stop screw of the damper to the end and release it sharply;
• Adjust the pressing of the screw and then click the flap. After stopping biting of the damper, check the screw with a nut;
• Place a multimeter probe on the idle contact and between the stop screw and the shutter;
• Turn the sensor body until the voltage starts to change and the damper opens;
• Secure the screws.

Air leaks in the car leads to a depletion of the fuel mixture, which, once it gets into the cylinders, ignites badly. For this reason, there is not only a loss of engine power, but also a periodic shutdown of its operation. This is especially evident when trying to start the car in the morning, when starting off - the engine chokes, does not gain momentum.

We are looking for air leaks

Since structurally injection and carburetor engine differ, especially their fuel and air systems, then we will consider the possible places of air leakage separately.

Injection cars:

1. Vacuum booster and its hoses;
2. Idle speed regulator (if any) in the area of ​​the sensors;
3. Intake manifold gasket;
4. Adsorber purge valve;
5. Throttle assembly gasket;
6. Nozzles (through O-rings);
7. Branch pipe between the throttle assembly and the air filter.
8. Crankcase ventilation system branch pipes.
9. Receiver studs.

Carburetor:

Items 1, 3 above are also characteristic of carburetor engines. Further more attention should be paid to the carburetor, since it is there that most often sucks air, namely:

Symptoms

It is important to understand that a strong depletion of the fuel mixture will cause a corresponding error on the instrument panel (injector) - this will indicate a large air leak, which will exclude the stable operation of the engine.

A slight depletion of the mixture will become one of the reasons for floating idle speed, which the ECU will somehow still be able to correct.

Symptoms of air leaks are not difficult to distinguish from any other, these are:

1. Difficult starting of the engine;
2. Increased fuel consumption;
3. Floating idle turns leading to a stop of the motor;
4. Decrease in power.

It is worth explaining a little here.

As for item 2 - when air is leaking, you have to drive in a lower gear more time, while the gas pedal must be squeezed almost to the floor, keeping the increased speed.

According to claim 3 - idle speed is poorly kept, and at 900-1000 rpm the car can stall. Many owners of carburetor cars immediately try to remedy the situation with the help of the quality screw and the amount of the fuel mixture, but as a rule, this does not help, since the excess air does not go through the idle channel, but, for example, a gasket under the carburetor.

According to claim 4, in addition to air leakage, other reasons can also lead to a drop in power, it all depends on which systems are structurally implemented in the engine.

Reduced idle speed is typical for MAF systems, where a mass air flow sensor (mass flow sensor) is installed in the intake tract - errors in its operation are possible.

In systems with an absolute pressure sensor (with a MAP sensor), errors in the lambda probe, misfires, and again a lean mixture can lead to a drop in power.

Many car owners make the mistake of changing the IAC or DFID when floating idlers. You don't need to do this. First, diagnose the engine for possible air leaks in the following ways.

We identify air leakage in the intake manifold

The essence of the problem lies in the fact that in engines with the above systems, excess air enters the combustion chamber.

It is already sucked in after the mass air flow sensor / MAP (absolute pressure sensor). As a result of this, the ECU receives data that is at odds with the real ones and from this the motor does not work correctly.

One of the problem areas is the gasket between the intake manifold and the cylinder head. Here air leakage can be minimal, it is difficult to visually identify minor damage and therefore not everyone pays attention to this place.

But seals in the form of gaskets, sealant can also pass in other places, the reason for this may be:

1. Decrease in their elasticity due to overheating or long service life;
2. Frequent use of cleaning agents for throttle assemblies, carburetors. These agents gradually soften the seals, which contributes to air leakage.
3. Mechanical impact on the gaskets if they are incorrectly replaced.

Air leaks in the manifold

Typical manifold air leaks are:

1. Microcracks in air ducts;
2. Loose connections;
3. Through the hoses of the vacuum brake booster;
4. Through the seals of the fuel injectors.

It is through these places that excess air, which is not taken into account by the mass air flow sensor, enters the combustion chamber.

We are looking for air leaks

There are many methods for finding places for air leaks, we will tell you about the most effective ones:

1. Forced shut-off of air supply to the engine.
2. The use of a smoke generator;
3. Compressed air;
4. Clamping hoses;
5. Wetting of probable places of suction with gasoline, carburetor cleaner, HP 40 or other flammable liquids.

Overlapping air

The essence of the first method is to disconnect the pipe from the air filter and close it. This will check if air passes through the seals in front of or behind the flow meter.

Algorithm of actions:

1. We unscrew the air duct in the area of ​​the air filter;
2. We start the car;
3. We close the hole in any possible way.

If after the flow meter (mass air flow sensor) the branch pipe is strongly compressed (residual air is sucked in), and the motor stalls, this is normal. And if the engine continues, albeit intermittently, to work, then by the hiss, which is likely to occur, it is possible to determine the place of air intake.

The disadvantage of this method is that when the engine is running and the corrugation is blocked, the oil can be drawn into the throttle unit through the oil through the reflectors. This is especially dangerous on motors with high mileage or after overhaul.

Smoke generator suction test

Many will notice that checking the air leakage by the smoke generator is done at the service station and not everyone has such a device in the garage. But who prevents you from making a smoke generator yourself with your own handles, because in reality, there is nothing complicated here.

Prepare:

1. 12V car compressor or conventional pump.
2. Food container with a volume of at least a liter. Please note that the container must have a tight lid, preferably a silicone one.
3. Two tubeless nipples. One should have a spool through which the pressure from the compressor will be supplied, in the second - unscrew the spool, since smoky air will be supplied to the system through it.
4. 2-3 cigarettes.

Make holes at the same level on both sides of the container and insert the tubeless nipples into them. A sealant can be used to seal.

Connect the hose to the nipple without a spool. The hose can be taken from the return flow of the purge valve.

Further procedure:

1. Disconnect the flow meter inlet from the air filter and close it in any way possible.
2. Disconnect the crankcase ventilation hose and plug it. Connect the hose from the container instead.
3. Insert the smoked cigarette with a filter into the nipple without a spool and close the lid tightly.
4. Connect the compressor to the first teat and turn it on.

The injected air will create pressure, the whiter cigarette smoke will begin to spread through the system and where there is a suction it will start to come out.

Another variation of the smoke generator.

We pinch the hoses

In this case, you need to be careful, since air leakage is detected when the car is running.

The essence of the method is that at the first stage the places of air hissing are detected by ear, and at the second stage, when the hoses of the vacuum amplifier, the fuel pressure regulator and others going to the intake manifold are pinched and released, the engine operation is monitored.

If there are any changes in its work during the above described manipulations, then a specific area will be checked in depth.

Spraying method

This method must be used with caution so as not to burn the car because you will have to use flammable liquids (gasoline, carburetor cleaners, etc.). Do not warm up the engine too much and use open fire.

The essence of the method is as follows - combustible vapors, for example, from gasoline, must enter the system through the supposed place of air leakage. As a result, the mixture will be enriched and the engine operating mode will change.

To accomplish your plan, fill the syringe with a combustible mixture and start the car. Gently spray liquid with a syringe in places where the likelihood of air leaks is greatest, and these are:

1. All branch pipes and their connections from the air filter to the valve cover;
2. Injector gaskets and between the block head and the intake manifold;
3. At the junction of the choke pipe and the receiver.

An increase in engine speed will indicate that a flammable liquid enters the system through this place, which means it sucks in air here.

Second spraying method

In this case, not a combustible mixture is used, but a soapy solution with a spray. Any detergent diluted with water can be used.

To implement the method you need:

1. 12V car compressor (foot or hand pump) with adapter for inflating mattresses (usually included).
2. Spray bottle with detergent.
3. Cellophane bag.
4. Rubber nipple of suitable diameter and length of 1.5 meters.

Procedure:

We turn on the compressor. It will be noticeable how the corrugation of the air supply is swollen.

Then listen carefully where the hiss is coming from. We moisten all possible places of suction with a soapy solution. Pay attention to the nipples for connecting the branch pipes of the vacuum brake boosters, ventilation ducts, and the sealing gum of the injectors.

In places where air is sucked in, bubbling of a soap solution will be observed.

Features of checking on carburetor engines

As we said above, the first thing you need to pay attention to on such engines if you suspect air leaks is the carburetor.

Check if all fuel goes through idle. To do this, start the car and disconnect the supply wire from the solenoid valve.

If the engine stalls, then the situation is simplified, since the valve is working. Remove it and unscrew the idle jet. Check the diameter of the orifice of the jet, it should be 0.40 - 0.45 mm (see the specifications of your carburetor). If the diameter of the nozzle is larger than according to TU, then replace it.

Start the engine and try to set XX by unscrewing the EMC. If this cannot be done and it is felt that the engine does not have enough fuel, it means that air is being sucked in somewhere.

Pay attention to possible bending of the carburetor flange. To check whether air is sucking under it or not, pour water under it.

If the engine starts to stall, then the problem is bending. In this case, we do not use a flammable liquid, it is so dangerous. See the video from Nail Poroshin for all the details.

Diesel engine

V diesel engine diesel fuel enters the cylinders bypassing two fuel subsystems - low and high pressure. As a rule, it is in the area of ​​low pressure that air is sucked in.

This can happen through many joints of pipelines, connections of elements of the fuel system, including the injection pump.

The problem is aggravated by another point. To reduce the cost of production of diesel cars on modern models, instead of traditional brass pipes, they use plastic products that wear out much faster.

Aggressive environment, vibrations, temperature drops - all this negatively affects their performance. This also applies to seals. As a rule, all this begins to manifest itself after 120-150 thousand km. mileage.

Often, an obvious leakage of diesel fuel when the engine is not running can indicate a problem area.

But when the car is running, when fuel is pumped from the tank, a pressure is created in the system that is below atmospheric pressure and therefore it is problematic to immediately identify air leakage.

Signs

The bottom line is that a mixture of diesel fuel with air getting into the injection pump when the engine is started does not allow it to perform its functions 100%, i.e. overloads it with a large amount of air in the fuel chamber.

When the car is already running, the fuel enriched with air foams and increases in volume. Therefore, at high speeds, the injection pump does not have time to pass it through itself.

As a result, when you try to start a diesel car in the morning, you have to oil it with a starter for a long time, while a small smoke from the exhaust pipe will be observed. And when driving, standing at traffic lights, the engine may stall due to insufficient supply of diesel fuel in the cylinders.

Causes

Reasons for air leaks in diesel cars:

1. Wear of rubber seals including fuel filters;
2. Loosening of clamps;
3. Damage to the fuel tank;
4. Wear and tear of hoses;
5. Damage in the return line;
6. Worn seals in the fuel pump cover, shaft drive, fuel lever shaft.

We are looking for problem areas

The easiest and most effective way to find air leaks is to pressurize the tank. Leakage of diesel fuel, hissing air will indicate problem areas.

In modern electronically controlled internal combustion engines, the amount of air entering the cylinders is strictly taken into account by special sensors. But when the air flow finds an alternative path through a loose connection of parts, the normal operation of the power unit is disrupted due to a significant depletion of the combustible mixture. Determining air leakage in the intake manifold or other places is not an easy task, the symptoms that appear are too similar to many other problems. Nevertheless, the problem of diagnosing this malfunction is quite solvable.

Signs and causes of suction

When a leak develops in the engine allowing additional air to pass through, the following symptoms are observed:

1. The first sign is "floating" idle speed. The engine draws in excess air, and the control unit, which analyzes the composition of the exhaust gases using a lambda probe, tries to correctly prepare the fuel mixture. But the mass air flow sensor (or DBP) does not take into account a part of the inflow, therefore the rpm is unstable (about the signs of a sensor malfunction).
2. The share of fuel in the combustible mixture decreases, hence the difficult start of the power unit "cold" when enrichment is necessary.
3. Due to the depletion of the mixture, engine power is lost - the car is harder to get under way and accelerate.
4. As the driver begins to press harder on the gas pedal and forcibly increase the revs, the fuel consumption increases.

There are several reasons why the tightness of the connections is broken and the engine sucks in air:

• deformation of adjacent planes (for example, the intake manifold to the cylinder head) as a result of overheating;
• too frequent use of automotive cleaning chemicals that can soften gaskets and sealants;
• leaky hoses or clamps on the vacuum take-off pipes in the engine.

On diesel engines, air is sometimes drawn in by the fuel pump through leaks in the line from the tank. In carburetors, the air flow path opens through worn axles and worn out dampers.

Where can air penetrate?

To check for engine leaks, you need to understand where to look. On motors equipped with an injector, air can be sucked in in the following places:

• a gasket on the cylinder head flange where the intake manifold is attached;
• body of the vacuum brake booster;
• vacuum take-off hose for the amplifier;
• throttle gasket;
• through nozzles with weak sealing rings;
• on the idle speed regulator flange;
• through the stuck valve of the canister - adsorber.

Worn carburettors, whose landing flange has buckled from high temperatures, often let air flow at the junction with the manifold. The second "sore point" is the throttle valves of both chambers, which become oval as a result of wear. Leakage occurs through the side gaps and causes a spontaneous outflow of gasoline from the main diffuser, which causes the engine to spin up to 2000 rpm at idle speed.

The weak link in a diesel engine is the fuel line from the tank to the high pressure pump. Plastic pipes and clamps lose their tightness over time and the pump, which creates a vacuum in the area, draws air through invisible cracks. It passes through the pipeline and is fed through the nozzles into the combustion chambers. The main problem is finding the problem: the leaking connections do not leak, since the outside pressure is higher than the inside one.

Fault detection methods

As a rule, the possibility of air penetration through a loose connection is remembered last, when other problems are excluded - failure of sensors, regulators, and so on. Meanwhile, there is a simple way to find air leaks - with the engine running, slowly close the throttle valve with your palm. If the motor does not stall, then a gap has appeared in the area after the mass air flow sensor, into which an additional flow seeps.

Note. Hearing a whistle or hiss at the place of the suction is not an easy task, since the noise of a running motor interferes. Therefore, this diagnostic method is not suitable.

1. Start the engine and wait for the idle speed to stabilize.
2. Push at several points the rubber tube leading from the power unit to the amplifier housing.
3. If the operation of the engine does not change, then there is no suction in this section. An increase in crankshaft speed will indicate a malfunction.

Check all hoses that take vacuum from the motor in the same way. If the crankshaft speed changes when squeezing and then releasing the pipes, look for a loose clamp or a crack in the hose.

The compressor will help to find air leaks through the throttle valve, manifold and other engine parts. A delivery hose with an adapter is screwed in in place of any spark plug, then the crankshaft turns to a position where the intake valve of this cylinder is open. Injecting air at a pressure of 4–6 bar, treat all joints with soapy water - bubbles will immediately appear at the problem point.

1. Draw up a syringe with a volume of 20 cm 3 gasoline.
2. Start the engine and wait for the idle speed to level out slightly.
3. Gently spray petrol on suspicious spots by squeezing fuel directly onto the gaskets.
4. If the suction goes through the intake manifold, then the pistons will suck in the spilled gasoline along with the air and the speed will increase noticeably. Be careful not to spill fuel on the electrical wiring.

The watering method works equally well for checking the manifold, nozzle seals, and throttle gasket. But it will not work to check the carburetor flaps with a syringe, since you cannot get close to them. To make sure that there is a working out and the formation of side slots, the unit will have to be removed and the walls of the chambers are cleaned of soot.

The line supplying diesel fuel to the injection pump of a diesel engine is more difficult to check. The method with the use of a compressor and soap suds is suitable here, but not every garage has such equipment. We'll have to go along the joints of the entire tube and diagnose the suction by the elimination method. Pour over connections diesel fuel meaningless - the effect will be insignificant and you will not hear changes in the operation of the motor.

One of the newest diagnostic methods involves the use of a special device - a smoke generator. The connection is made, as is the case with the compressor, to the spark plug hole of any cylinder. After starting the smoke generator, it is easy to find the point of air penetration. It is recommended to use a halogen lamp to better see the rising plumes of smoke.