The engine troubles on gas: why it troubles when the pedal is pressed sharply or at idle, what are the reasons for this when switching and reviews about them

Last updated April 2, 2022 at 12:25 pm

Finding the reason for the unstable operation of a car with gas equipment is often possible only with an integrated approach. The problem that causes the engine to stall on gas may be a malfunction of the engine itself.

If interruptions occur after switching to gas fuel, and the car is restored to gasoline immediately or after some time, the search for the source must begin with the gas gas system along the least path of resistance.

Reasons why the engine “troubles”

The engine may throb constantly or from time to time. General signs of engine vibration are as follows: at idle speed, strong uneven vibrations begin to penetrate from the engine compartment into the cabin, the sound of the running engine changes (it “growls”, goes from high “notes” to low ones, and back).

The unit begins to consume more fuel, and its power decreases, and obscene sounds are heard from the exhaust pipe, accompanied by thick white or black smoke. If at least one of these signs is present, it means that the “heart” of your car has problems with one or more cylinders.

If they are not eliminated in time, the consequences can be very disastrous - up to and including a major overhaul of the power unit. Let's characterize the most common reasons why an engine stalls - there are four of them:

late or early ignition of the air-fuel mixture (FA);
uneven entry of fuel into the engine cylinder;
lack or excess of air in the combustion chamber of the cylinder;
drop in compression level.

Reason #1

. If the air-fuel mixture ignites in the cylinder earlier or later than the specified period, then the spark plugs are to blame, which produce too weak a spark, or the formation of a spark occurs untimely. Weak sparking occurs due to the fact that harmful deposits (carbon deposits) accumulate on the spark plug body and its electrodes, which interfere with spark breakdown.

Another reason for a weak spark is the destruction of its insulator.
In the place where the insulator has collapsed, a soot spot forms, which prevents the formation of a normal spark. If there is no spark at all, then there may be several reasons: a worn spark plug cap, a failed high-voltage wire (supplies current to the spark plug), a breakdown of the ignition coils or switch.

The latter phenomenon is quite rare, but it would not be superfluous to check the condition of the switch, which controls the ignition distribution.

Reason #2

. Uneven entry of fuel into the cylinder, when a smaller amount of gasoline or diesel is poured into the combustion chamber, often occurs due to a malfunction of the fuel pump parts (pressure part or pressure reducing valve) or the pressure valve in the fuel supply system.

If more fuel than necessary gets into the cylinder, the problem probably lies in the fuel injectors - they are dirty or out of order.

Finally, another “fuel” reason for engine throttling is a malfunction of the electronic control unit (ECU) of the power unit, which can erroneously increase or decrease the supply of gasoline/diesel to the cylinder.

Reason #3

. Excess air in the cylinder is a sign of depressurization of the air supply system, which includes the air filter, intake pipe hose, throttle pipe and receiver. A lack of this important component of the air-fuel mixture in the cylinder can be caused by a dirty air filter or broken throttle valves.

A malfunction of the mass air flow sensor or throttle position sensor, which the ECU perceives as a request from the engine to add or reduce the amount of air into the combustion chamber, can also cause the engine to trip.

Reason #4

. Low compression or its complete absence is perhaps the most serious reason why an engine misfires. This is the first sign that the pistons or valve in an idle cylinder are burnt out, or the piston rings are completely worn out. This cannot be done without serious repairs to the power unit.

In addition to the common reasons why an engine misfires, there are also secondary ones. They are spoken of when the engine starts to run periodically - “cold” (at idle speed) or “hot” (at medium or high speed).

The most common malfunction here is the valves: when their gap increases at idle speed, the engine trips, which goes away as it warms up (the gap is restored). And vice versa, the gap increases when the engine reaches operating temperatures - that’s when it starts “hot” with all the signs described above.

Diagnostic methods

If all the signs that the engine is malfunctioning are present, it is necessary to diagnose it and determine which cylinder has failed and for what reason. You can carry out the check yourself, or you can take the car to a service station, where its power unit will be subjected to detailed computer diagnostics.

In most cases, you can determine the reason for the engine tripping yourself, but if the cylinder refuses to work, for example, due to low compression, it is better to seek help from an experienced mechanic.

Step 1.

Determine the problem cylinder. We check the operation of the cylinders with the engine running, so all safety measures must be observed. We turn on the ignition, open the hood, listen to the engine. We remember what sound it works with. We begin to disconnect the high-voltage wires going to the spark plugs one by one.

When the working cylinder is turned off, the engine begins to rev with double force. If you disconnect the spark plug on the non-working cylinder, the behavior of the engine will not change. Another way is to not touch the high-voltage wires, but one by one turn off the chips that control the supply of fuel from the injectors to the cylinders.

If one of the chips is turned off, the operation of the engine will not change - this is how we detect a malfunctioning cylinder.

Step 2.

We check the condition of the high-voltage wire and spark plug. We disconnect the high-voltage wire and carefully inspect it. If we notice damage to the insulating layer, it means that the cause of the malfunction is in the wire.

It would also be useful to check the integrity of the current-carrying core - if it is broken or burnt out, then a breakdown or internal resistance occurs (we measure it with a multimeter, check it with normal readings), which interferes with the normal supply of current to the spark plug.

Gas fuel filtration

A gas-powered car may fail due to untimely replacement of gas filter elements or their poor quality. This is usually accompanied by a loss of throttle response when the gas is pressed sharply.

It is advisable to change coarse and fine filters in the interval of 8-10 thousand mileage. Depends on:

operating conditions
gas quality
flow tube material (copper oxidizes)

Copper oxides in a coarse gas filter

In addition, sometimes the filter mesh of the multivalve intake tube becomes clogged. To clean it, you will need to dismantle the cylinder valve block. When installing HBO, the mesh is often simply not installed.

Why does the engine run rough on gas, but runs smoothly on gasoline?

The problem when the engine stalls is familiar to many motorists and, most often, each of you knows where you need to “dig” to understand the cause of this breakdown. However, in the case of gas equipment, not everything is so simple, and sometimes in order to understand why the engine is running on gas, you have to suffer for a very long time in search of a probable cause.

The main problem is that the design of gas equipment is not known to everyone; in addition, the search process is complicated by the fear of the gas itself, which, as you know, is a flammable substance. In this article I will try to understand the problem when the engine runs rough on gas , but works fine on gasoline.

The engine runs fine on gas, but runs fine on gasoline - reasons

The easiest and most correct way to look for the reason why the engine is shaking on gas is to connect a diagnostic scanner. With its help, you can find out exactly the cause of the malfunction based on the error recorded in the ECU. However, if there is no scanner or you do not have the opportunity to visit the gas workers, you can try to find the cause of the breakdown at random.

1. Check gas filters. If you have replaced gas filters a long time ago, it would be a good idea to check their condition and replace them if necessary.

2. If replacing gas filters does not lead to anything, we continue our search. Check the condition of the spark plugs; often the engine stalls and stalls on gas precisely because of problems with the spark plugs.

3. BB wires. High-voltage wires can cause tripping, but in this case, most likely, the engine will run unevenly on gasoline.

4. Gas reducer. If the gas reducer is configured incorrectly or is very dirty, it is quite possible that this kind of trouble will occur (idle speed floats, jerks while running on gas, engine roughness ).

Clean the gas reducer, replace filters and, if necessary, replace worn rubber gaskets, this will require a repair belt. kit for the corresponding gearbox.

In some cases, it may be necessary to completely replace the gas reducer.

5. Gas injectors. A problem with injectors can often manifest itself in the form of tripping. Due to malfunctions of the injectors, ignition of the gas mixture occurs intermittently, as a result, gas consumption increases, the engine suffers, and detonation is also possible.

A common problem with injectors is the so-called “non-holding”. You can check this on a diagnostic stand or at home, having some experience.

Symptoms of malfunctions and solutions

As soon as the first signs of malfunctions of the 4th generation gas equipment appear, you should sound the alarm, find out the cause and carry out repairs. Each brand of HBO has its own weaknesses. For example, a table of faults of the 4th generation alpha gas equipment helps car service technicians in their work.

There are not so many characteristic symptoms of breakdowns, and the solutions are not complicated if you understand the essence of the problem from the beginning.

The engine does not switch from gasoline to gas

If a gas car switches to gasoline, or there is no automatic switch to gas at all, there are several reasons:

Malfunction of the temperature sensor, which is located in the gas reducer.
Insufficient heating of the gearbox (possible reasons: low level of coolant in the system, air lock, freezing of coolant at low negative air temperatures).

Read more about the problem of not switching from gasoline to gas here.

Excessive gas consumption

In order to understand whether there is excessive gas consumption, you should calculate what consumption is optimal for your car. In the article about gas consumption by Lanos and Sens cars, we described in detail how to calculate gas consumption rates in summer and winter.

Increased gas consumption can be caused by several factors, namely:
Worn, dirty or incorrectly calibrated gas injectors.
Clogged or dirty air filter.
Problems with the gearbox (not warming up enough, physical wear, requires adjustment).
The oxygen sensor does not work.

The car runs on gas

In the life of every motorist there is a situation when the engine misfires, often this means a banal problem with the spark plug or a couple of other well-known breakdowns. But when it comes to the LPG system, sometimes it can be quite problematic to understand why the engine stalls on gas, but works fine on gasoline, and in this case one cannot do without an integrated approach and analysis of the situation. The car runs on gas for various reasons, but often, even a knowledgeable person is afraid to get into the gas installation and understand the problem, entrusting the troubleshooting to specialists.

In most cases, such caution when working with a gas system is justified, because gas is a flammable substance, and any leakage can result in serious problems. But if there is no opportunity to contact specialists, and the car stalls and stalls when running on gas, you can try to figure out the problem yourself.

Finding out the reasons

Let's try to highlight several reasons why your iron friend struggles on gas. To determine the cause, it is best to use a computer (laptop), connecting it through a special diagnostic cable to the electronic control unit of the gas system, if we are talking about the fourth generation of gas equipment and higher. If your car has a 2nd generation HBO or there is no way to connect a laptop, you will have to look for the reason the old fashioned way, eliminating step by step the weak points of the system.

HBO filters

First of all, you should check the gas filters; this advice is especially relevant if you have not done annual maintenance on your gas installation, and the car has been running on gas recently. We described in detail how to replace the LPG filter, drain the condensate and perform a complete maintenance of the system in this article.

Candles

The second weak point is the spark plugs. It is necessary to check the gap on the spark plugs, it should be the same on all spark plugs and be within the range of 0.7 -0.9. If scale is visible on a spark plug, this is a clear sign that it is “broken,” and the LPG system is not working on gas.

It is also worth noting that there are special spark plugs on sale that are designed specifically for engines that run on gas, it would be wise to purchase them.

Gearbox

One of the most common problems with an engine running on gas is contamination or incorrect adjustment of the system's gas reducer.

But in this case, the problem of a gas-powered car will include floating idle speeds, and jerks or loss of power when the engine is running on a gas installation. To begin with, try limiting yourself to cleaning the gearbox and replacing the filter in it (if there is one, of course).

If this does not help, you should take a closer look at the repair. kit that will fit your gearbox, and replace the used rubber gaskets in it.

Injectors

A fairly common problem that a car runs on gas but not on gasoline is gas injectors. There can be many reasons for the malfunction of injectors, ranging from their contamination and sticking to simple wear and tear of the design of one of them.

To determine that the injectors are to blame for unstable engine operation on gas, the easiest way is to place them on a special diagnostic stand.
The second option is to temporarily replace the injectors with a set that is known to work.

Sticky and dirty injectors can be washed, but worn ones will have to be replaced. To be fair, it is worth noting that quite often technicians at service stations, in case of wear of the injectors, suggest using a repair belt. kit, not new injectors. However, given that the price of rem.

kit fluctuates within 50% of the price of new injectors, and considering the cost of work to replace worn-out elements, agreeing to such an offer or buying new parts is not an easy choice.

You should also remember the fact that serviced injectors should be serviced at least once every 30,000 km. Maintenance consists of replacing damper rings and other worn elements. Remember that after replacing the injectors, a specialist must calibrate them and configure the system while the car is moving.

Wires

The last of the most common reasons is wear of high-voltage wires, but in this case the machine will not only run on gas, but also when running on gasoline.

Air leak

Leaky or loose gas system connections can cause air leaks, which in turn will lead to loss of power and unstable engine operation.

In conclusion, I would like to note that we have identified only the most common reasons that a car stalls on gas, in reality there are many more reasons, and if you were unable to identify the fault yourself, you should contact a qualified technician who will carry out diagnostics and accurately determine and will fix the problem.

Why does a car with 4th generation LPG start to stall when switching to gas?