The car jerks on the gas

Installing LPG (gas equipment) on a gasoline car has become a normal practice for Russian motorists. After the rise in gasoline prices and horror stories about further price increases in the near future, motorists have to think about methods of saving. At the time of writing this review, on average, 95-grade gasoline costs about 48 rubles, and propane costs 22 rubles. Considering the fact that gas consumption is only 10% more than gasoline, there are obvious savings. Of course, there will be opponents of HBO who will argue that you will never pay for the installation, and the engine will wear out faster. But taxi cars with 400,000 km on the meter and gas have been proving the opposite since day one. Today we will not discuss the advantages and disadvantages of gas equipment for cars, but will talk about one of the disadvantages - unstable engine operation. Very often, car owners experience the car jerking on the gas at low speeds or at idle.

This problem is often related to the gas equipment itself, but sometimes it depends on other factors that will also have to be dealt with. Gas on the car will not always cause jerking. Very often, incomprehensible behavior of a car appears due to other factors that the motorist does not take into account. But in other situations, the culprit still turns out to be gas that is incorrectly configured or installed poorly. Today we will try to sort out this issue, and also give some recommendations on what to do in such a situation. Many people believe that jerking when driving on gas is normal. But in fact, this is a rather comprehensive indicator of one of the possible breakdowns. Often, to diagnose a specific breakdown, you will have to travel to several stations to obtain a combined expert opinion.

A trivial reason - poor quality gas or the need for maintenance

Gas equipment of the 4th generation is considered the most common today; they are trying to install it on cars with an injection system. The system contains several filters. Some manufacturers install a coarse filter in the area where the tank is installed. Also installed in the engine compartment is a small filter element for coarse cleaning, as well as a fine gas filter. They need to be changed once every 20-30 thousand kilometers or every 2-3 years. If maintenance has not been done for too long, the filters are clogged, which will cause a decrease in fuel pressure in the system.

Regarding gas quality, it is worth remembering the following:

bad gas is sold today at every second gas station, in Russia problems with fuel quality have not gone away, and this also applies to autogas, so you should carefully choose a gas station;
cheap and dirty gas quickly clogs filters, they lose capacity and actively reduce the quality of vehicle operation, as they do not perform their functions normally;
poor fuel burns worse than required by a gas installation, which also causes unpleasant features in the operation of the car, power is lost, and the quality of the car’s performance deteriorates;
consumption increases, since the driver has to constantly press the pedal in order to drive normally; under normal conditions, traction on gas and gasoline is almost the same, if there are no other breakdowns;
at low and idle speeds the car does not understand what to do, the computer either increases or decreases the speed, trying to balance between stopping the engine and an emergency situation.

You can fill up bad gas even at a very good gas station. No one is immune from troubles that can happen with fuel. It is worth choosing one station where propane is not too cheap and also suits you in terms of quality. It is at this gas station that you should refuel in the future. Experiments with the quality of gasoline may pass without a trace, but you will immediately feel the quality of gas in your car and experience the most unpleasant emotions in operation. This is important to remember when choosing a gas station.

The car jerks on the gas - what could be the reason?

Sensors - look towards electronics

The second reason for a car jerking on gas is the sensor system. In the 4th generation, several sensors are installed that transmit information to the ECU or to its own computer. The set may differ in different generations and modifications. For example, there is a gas mixture pressure sensor that controls the operation of the gearbox and supplies the mixture to the injectors. It is this that often causes problems with the car twitching at idle or low speeds. This sensor is also called a MAP sensor; it often fails.

The problem algorithm develops as follows:

one of the parts of the MAP sensor burns out, which is responsible for measuring the gas pressure in the system, and also measures the temperature in more modern installations, which is also important for normal operation;
further operation on gas becomes arbitrary, the speed can float or stop in any position, despite the optimal travel mode and good gas filling;
the next stage - the sensor misses the readings of the mixture temperature, which causes the supply of fuel to the injectors that is not heated to the optimal temperature, this also causes combustion problems;
the pressure on the injectors drops to critical values, and sometimes the supply is cut off altogether, this leads to an emergency switch to gasoline and errors in the gas system sensor system;
This damages the sensor even more, the operating parameters of gas-cylinder equipment become unclear, and you have to drive on gasoline until visiting a service station.

But the MAP sensor is not the only electronic part that causes such unpleasant operating features of the car. There are also a number of other sensors, the set of which greatly depends on the manufacturer and modification of the LPG systems. If you have a low-cost setup, you can simply replace the sensor kit. If the cost of automation is high, it’s worth going for diagnostics and finding out which parts are causing problems in your car’s system. This way you will save money on buying unnecessary parts.

Why does the car jerk on the gas? Causes and solutions to the problem

It often happens that a car equipped with LPG suddenly begins to work unstably under load: jerking while driving , as if the fuel was at the bottom. At the same time, the gas cylinder is full. And it’s good if you didn’t manage to get far from the gas man, but usually this happens at the most inopportune moment - when driving up a hill, for example. By switching to gasoline, the problem may disappear.

Practice shows that in 8 cases out of ten, the car jerks on the gas not at all because of the gas, but because of problems in the electrical part. The reasons are as follows:

Spark plug;
High voltage wires;
Ignition coils (ignition module).

Moreover, a defect in the electrical part may not appear when running on gasoline, or at idle speed on gas. The thing is that gas does not ignite as easily as gasoline, so the gas-air mixture requires more spark. Hence the increased requirements for the serviceability of electrical equipment and vehicle equipment.

The existence of spark plugs that are recommended for installation in a car with gas equipment is not marketing, but a necessity. They differ not only in clearance, but sometimes also in design. It's not difficult to change them.

As for the armored wires, it is not always possible to detect their malfunction in the usual way - by observing the operation of the engine in the dark, with the hood open, therefore, if the wires are “stale”, then they should also be changed.

The remaining 2 cases out of 10, why the car jerks while driving , are due to a malfunction of the gas equipment itself, and to errors in the ECU firmware. ECU settings and incorrect injector calibration manifest themselves immediately, and if there has been no external interference, then they are the last thing to blame. If necessary, you can “upload” new firmware, but it is better to entrust calibration to specialists.

But defects in gas equipment usually appear over time as a result of operation. They are mainly associated with air leakage, which occurs:

At connections of all gas distribution;
Along the body of the hoses themselves, as a result of drying out or chafing;
At the place where the “clap” is installed;
By a gearbox gasket damaged as a result of regular freezing.

To detect a malfunction, you need to “wash” all connections and suspicious places. If necessary, replace hoses and update connections.

Gas pressure - testing all theories of change

The problem of pressure on injectors does not only plague gasoline fuel supply systems. In gas equipment there is also the possibility of encountering such a nuisance. The thing is that pressure is built up in the gearbox, which tends to fail regularly. The gearbox can be repaired, but to do this you need to carry out diagnostics, buy a repair kit of spare parts and entrust the car to a specialist. It’s better not to do anything with your own hands in HBO systems. This may cause problems later on.

So, gas pressure changes for various reasons:

clogged filters - we have already discussed this problem, but it is worth mentioning it again in the context of talking about pressure on the injectors; cleaners should be changed in a timely manner;
a non-working MAP sensor or other pressure sensor installed in your LPG system, you just need to replace it, some sensors can be repaired by replacing the electronic measurement system;
the gas temperature sensor has broken down, which signals the possibility of switching to gas when warming up, and is also responsible for optimal heating of the gas mixture in the reducer before supplying it to the system;
the injectors are clogged, but this is only possible if the pressure is measured at the outlet; the pressure is usually measured by connecting a pressure gauge at the inlet of the injector assembly;
If there are kinks in the tubes and other problems, you should examine the condition of the parts and connections in the LPG system to make sure there are no trivial problems with the gas supply to the injection system.

As you can see, there can be a lot of reasons. Sometimes the reason lies in the gas installation control unit or emulator, which is designed to use the standard ECU as a gas unit. Everything is quite simple - you need to connect computer diagnostics of the equipment and check the condition of the sensors. This can be done at a special service, so as not to waste your own efforts and not look for expensive equipment. It’s easier to turn to specialists, but you need to choose specialists specifically for gas installations.

Didn't you see the entrance?

To detect a breakdown, it is necessary to supply a smoke mixture under pressure into the system. And soon the inlet location will clearly reveal itself. You can normally “wash” all questionable surfaces and connections the old fashioned way. The “wounded” node will have to be updated.

Excess air can also enter in a “legal” way, through the air filter. To reduce it, a bushing is placed in the supply hose. When returning to gasoline, the bushing is removed. By the way, without monitoring the antifreeze level, when it decreases, the gearbox circuit mainly suffers. As a result, the gas does not have time to evaporate and remains in a liquid state.

So it turns out that our car is our car. And only we are responsible for its maintenance. Either we do it ourselves or we insist that the master correct his oversights efficiently.

Other reasons not related to HBO

If your car starts to jerk at low speeds and the idle speed starts to float, first switch to gasoline. Try driving a few kilometers on gasoline and see if the problem goes away. If everything remains the same, then the problems are definitely not with gas equipment. If the twitching has passed, then the cause must be sought in the HBO systems. There are several common situations that can be called classic for gasoline cars, and they do not depend on the presence and operation of a gas installation.

These situations are as follows:

gearbox - it is quite possible that twitching at certain speeds or at a specific speed is due to a malfunction in the gearbox; this can only be checked by diagnostics;
clutch - very often the culprit for problems with jerking at the start or jerking of the car during acceleration is a worn basket, a faulty release bearing, this is a standard situation;
throttle position sensor (TPS) - these parts break quite often, and the breakdown disables normal computer engine control, so problems develop;
idle speed valve (sensor) is another device that, if broken, can cause jerking while driving, malfunction of the idle speed in the car, constant floating speed;
The absolute pressure sensor (MAP) is also one of the electronic systems that causes twitching and other troubles when it breaks down; the ECU does not receive the necessary signals about air pressure.

As you can see, most problems in this case are related to sensors and electronics. These are natural breakdowns in our conditions, where when repairing and restoring cars, buyers actively save money and use cheap Chinese electronics parts. Such sensors quickly break down and do not perform their tasks. Therefore, you should think seriously before purchasing low-quality automation parts, which in the near future will require even greater investments in repairs and replacement of equipment.

We suggest watching a video on the topic of jerking a car on gas:

The problem is in HBO

If all of the above options have been checked, and when you sharply press the gas pedal, the car jerks while driving as before, then you should look for the problem in incorrectly configured or failed gas equipment. Basically, the problem with gas equipment lies in unregulated air leaks, which results in jerking of the car. To identify such a malfunction, you should take a closer look at:

Connections of all gas elements. Due to long-term operation, depressurization of the connecting elements of the system is possible.
Lines and rubber hoses that may dry out due to active use.
"Anti-clap." You need to carefully check the cotton elastic and the installation location.

You can identify the location of air leaks by “washing” all of the above system elements. If a defect is detected, the hoses or connecting elements should be replaced, and then the tightness of the system should be checked again.

It would be a good idea to make an appointment with an experienced diagnostician, who, by connecting the car to a computer, will identify problems with the ECU settings, calibrate and clean the injectors, and also identify other possible problems.

One of the possible options for the fact that the car jerks when you press the gas pedal while running on gas may be that maintenance of the LPG system was not carried out in a timely manner. We recommend that you undergo maintenance at least once every 10,000 km, and in the case of 2nd generation gas equipment, drain the condensate from the gearbox and change the gas filter 2 times a year.

Don’t wait until your car refuses to move at all; the first time you notice that the car is jerking on the gas, try to solve the problem as soon as possible and do not put it off so as not to aggravate the situation.

Source

Let's sum it up

Modern cars require high-quality fuel and good maintenance. If these factors of their operation are violated, problems with technical capabilities appear, the machines begin to show a variety of problems and, in general, do not want to serve. When the car jerks when driving on gas, it is not recommended to continue using the car. We need to find the reasons why transport behaves so inappropriately. After searching for the reasons, it will be possible to completely restore the HBO system and return it to normal operation. But this is only possible after a full diagnosis.

It is recommended to undergo a complete maintenance of the gas installation once every 3 years, including replacing all filters, checking sensors, setting and calibrating injectors, and overhauling the gearbox. Also in this process, the technician will search for air leaks, which may be the cause of various problems in the vehicle system with LPG. You should carefully consider the process of repairing and restoring gas equipment. Otherwise, operating the equipment will be impossible, and you will spend more and more money on gas due to increasing consumption. Have you ever experienced your car jerking at low speeds?

Sometimes owners of a car equipped with HBO begin to notice unstable operation of their car at idle or under load. During movement, strange jerks appear, and the power leaves much to be desired. Why does it happen that the car jerks on the gas, how to avoid such a state of the iron friend, and what could be the reason for the jerks while driving, we will talk in today’s article.

Jerks of a car with 4th generation gas equipment when accelerating at low speeds

After installing the 4th generation HBO, operating the car, in addition to saving money, adds hassle to the driver in the form of system malfunctions. One of them is twitching at low speeds at the beginning of movement.

If the car jerks when driving on gas, but after switching to standard fuel the engine operation returns to normal, finding the cause may require special knowledge and equipment. However, self-repair is also possible; often the problem of jerking lies on the surface.

Mechanics

Over-depletion of fuel assemblies due to unaccounted air in many cases is the cause of jerks. Find out more about how to find and fix air leaks with your own hands here.

Injectors

If, after checking the electrical system, the car still starts to jerk when you press the gas pedal, the first thing you should do is inspect the fuel supply hoses to the injectors. Their length and size must be the same (max. 25cm). Bends, fractures, cracks, and gas leaks are excluded.

Let's move from simple to more complex. For further diagnostics, you will need a cord and a 4th generation HBO setup program.

First, you need to check the functionality of the electromagnetic coils of the injectors by turning them off one by one. Perhaps some coils are working intermittently. Injectors may also function with uneven fuel supply (inconsistent), reasons:

Also, shocks may appear during acceleration at low speeds (up to 2500 rpm) or a sharp start, due to the increased opening time of the injectors.

To avoid twitching when releasing the gas to idle and further accelerating, turning off auto-adaptation at the adjustment stage will help. For some cars it is simply useless.

Reducer-evaporator

Incorrect selection of the gearbox for the engine power or its malfunction, for example, destruction of the membrane (a rich mixture is obtained), will also cause failures, especially under load at high speeds.

To detect a diaphragm rupture, it is necessary to remove the vacuum hose from the suction manifold side and check it for gas leaks. In this case, the machine must run on gas fuel.

Quite often, the car jerks on gas if the evaporator does not heat up due to an incorrect connection. Setting the gearbox according to fuel pressure also affects the jerking of the car in motion.

Timely draining and washing of the evaporator reducer from condensate will help get rid of “kicks”, but this is a condition for 2nd generation LPG reducers.

Main causes of malfunctions

Below we will highlight the main reasons for the malfunction of the 4th generation LPG, which are quite common, but first of all, before looking for the reasons in the gas installation, you should make sure that the car runs stably on gasoline.

The reasons for unstable LPG operation are not always related to gas; first, pay attention to such vehicle components as spark plugs and high-voltage wires. Quite often, these elements influence incorrect operation and lead to the fact that a car equipped with a 4th generation gas system stalls or loses power.

Engine speed fluctuates on HBO

There are several reasons why the engine does not idle when running on LPG:

The first thing you need to do is eliminate the electrical component (spark plugs and high-voltage wires);
If you have not changed gas filters for more than 10,000 km, you should replace them.

Closing on the go

It jerks when it’s hot, which means no one is watching the resistance of the explosive wires and spark plugs when moving. Normally, the resistance of armored wires is up to 15 kOhm, spark plugs are up to 6.8 kOhm. The higher the resistance, the stronger it jerks, the sooner the closing coil will break. By the way, the resistance of spark plugs is increasingly burning out, and due to an increase in breakdown voltage, an interturn short circuit occurs in the coil. Every third person drives with it on gasoline, and they experience a mini-slip, sometimes with a twitch. On gas, this is immediately evident, because the combustion period is less than 1 ms and the first LPG in power mode will certainly have a pop, and the fourth one will fail and jerk.

The most important measure that significantly influences fuel consumption, efficiency and stability of gas engines is the ignition timing, which marks the time of ignition of the gas-air mixture. This indicator is based on a multi-level relationship with temperature, load and at what speed the engine is best tuned.

Incorrect adjustment of the advance angle often leads to gas detonation, followed by jerking, and the car jerks. This significantly reduces both power and resource, which engine could be more interesting.