Any internal combustion engine, namely the one installed under the hood of your car, does not run on gasoline, gas or diesel fuel, but their mixture with ordinary air. After all, even from the physics course in high school, many remember that their combustion without oxygen access instantly stops. Whereas if there is a lot of one of these components, or, conversely, a little, the motor will work unstable, intermittently, not providing sufficient power / thrust, or even stall.
What is a lean mixture
It's very simple, a lean mixture is a fuel-air mixture in which there is not enough fuel. As a rule, the classic, correct figure for the ratio of gasoline to air is 1 to 14, a lean mixture is already 15-17 liters of air per liter of fuel, and a lean mixture is 17 or more liters of air. But this is only for use on roads located on the plain: in the mountains, where the air is thin, these figures will be different.
Signs and reasons for the formation of a lean mixture
At the same time, it is very easy to diagnose it:
- The most the simplest and most obvious - the car stalls when driving. And not only when driving uphill, when this can be attributed to an incorrectly selected gear, but when driving on straight, flat roads. However, this is only when the mixture is really lean.
- Another situation is when the car twitches while driving. Especially if you are driving not in a fully loaded, but empty car on a flat road. Although in this situation it is impossible to say unequivocally that a poor air-fuel mixture is an indispensable reason. You may need to check other vehicle systems such as the exhaust system.
- Another sign - when driving, the car “shoots”. Although more and more often in new cars this is not due to a lean mixture, but to a malfunction in the exhaust system, this symptom is obvious. Especially when the unstable exhaust does not appear from time to time, but constantly, since with single pops the situation is the opposite: the mixture is too rich, and the remnants of gasoline, not burnt out in the engine, burn out in the muffler, ignited by a hot pipe.
- The color of spark plug carbon can also tell a lot about the composition of the mixture. If it is:
- brown, then everything is fine, there is an optimal amount of air-gasoline in the mixture;
- white, or, alternatively, light, then there is a lot of air in the mixture, and it is poor;
- black candles - excess gasoline that does not burn out completely;
If there are signs of a lean mixture, this diagnosis can be confirmed in several ways:
- If the machine is equipped with an on-board computer, the "Check Engine" indicator on the dashboard will light up and P0171 will appear in the error list.
- By contacting a specialized workshop, you can test the operation of the engine using a gas analyzer sensor, which is installed in the exhaust pipe.
- Finally, you can use the simplest wired or Bluetooth OBD scanner, which costs only a few dollars on Aliexpress, a smartphone and the corresponding software.
Look for the cause of the lean mixture based on the diagnostic results and errors that appear with P0171. Typical reasons are:
- Problems with sensors ( DMRV, TPS, DBP, oxygen sensor ). Incorrect sensor information usually results in an incorrect fuel / air mixture.
- Problems with EGR valve. The valve can allow more exhaust gases to flow into the engine than necessary.
- Problems with timing. Incorrectly aligned marks or tensioner problems can also lead to this problem.
- Problems with the fuel supply (faulty fuel pump, clogged fuel filter or injectors).
- Excess air supply through a crack in the hose or a loose connection in the air supply system.
See also : Symptoms of spark plugs.
Potential Effects of a Lean Mix
Prolonged operation of a vehicle engine running in a lean mixture can cause:
- Burnout of the valve cover / valves themselves. At idle, the engine stalls, and the driver is forced to constantly maintain elevated. The effect of this is predictable: repairs that will cost a pretty penny.
- Excessive load on the cooling system. Due to the lean mixture , the temperature of the engine will always be higher than normal, so the wear of the cooling system elements will be premature.
- Increased fuel consumption. Especially if you are used to driving to the fullest, then when driving you will have to constantly switch one or two gears down, which will definitely affect the frequent visits to the gas station.
Therefore, if you find that your car is running on a lean air-fuel mixture, then do not delay the repair, but go to the service as soon as possible. Moreover, repairs can be quite penny, for example, it is not uncommon to get by with a simple cleaning of the throttle valve.
See also : Why the car starts and stalls after a few seconds.