Why the engine does not develop speed: possible causes and solutions

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:42

Reducing the number of engine revolutions significantly affects its power and traction. If suddenly your car has lost its former agility, you should think about diagnosing it, because such symptoms do not bode well.

In this article we will talk about why the engine does not develop speed and what this may be connected with. We will also consider the probable causes of power loss in the power unit and methods for their elimination.

Signs of malfunction

Determining that the engine is not developing the speed it should be developing is not difficult, especially if you have driven a car before and know its native characteristics. Those drivers who have encountered a similar problem in their practice know that a decrease in power is characterized by sluggish acceleration, loss of dynamics, traction, as well as engine overheating and increased fuel consumption. Sometimes these processes are accompanied by blue or even black exhausts.

You press the accelerator pedal and the engine does not rev well? Pay attention to the tachometer. A serviceable motor should instantly respond to an increasethe amount of fuel supplied to the combustion chambers by increasing the number of rotations of the crankshaft. And if this does not happen, you need to urgently look for a malfunction.

Main reasons

There can be many reasons why the engine does not develop speed. Here is a list of the most common ones:

• power unit not warmed up to operating temperature;
• low or, conversely, excessive fuel level in the float chamber;
• Faulty accelerator pump;
• clogging of jets, carburetor channels;
• air leak in intake manifold;
• ignition timing incorrectly set;
• Valided valve timing;
• violated spark plug gaps;
• clogged air or fuel filter;
• malfunction of mass air flow sensors, crankshaft position, throttle position, detonation;
• insufficient compression in cylinders, etc.

As you can see, the list is quite extensive, although it cannot be called complete. Let's consider in more detail the listed malfunctions.

Cold engine

It would be wrong to demand full power from the power unit until its temperature reaches the operating temperature (900C), especially when it comes to a carbureted engine. A cold engine does not rev to its full potential, even with the choke fully closed. Fuel mixture before entering the combustion chambersmust be warmed up. Otherwise, the car will “twitch”, and the engine will stall and detonate. So, if your car is equipped with a carbureted engine, do not rush to leave until it warms up.

Fuel level in float chamber

The fuel level in the float chamber can also affect the operation of the power unit. If it is lower than it should be, the concentration of gasoline in the combustible mixture decreases. Because of this, the engine does not develop power. At an overestimated level, the mixture, on the contrary, is too enriched, but more than the norm enters the combustion chambers. Before entering the cylinders, it does not have time to warm up in the intake manifold, which leads to detonation and loss of speed.

The fuel level is adjusted by bending (bending) the float mounts.

Accelerator pump, channels and carburetor jets

Continuing the theme of the loss of power of the carbureted engine, one cannot but mention the accelerator pump. It is on its serviceability that the response of the power unit to pressing the accelerator pedal depends. Most often, the problem lies in the supply of fuel, and the “spouts” of the sprayer are to blame for this, through which gasoline is supplied in a thin stream. To check the performance of the carburetor accelerator pump, you will need to remove the air filter so that a view of the first chamber opens. Next, you need to open the throttle and hold it for a few seconds. At the same time, a thin (about 1 mm) stream of fuel should escape from the “nose” of the accelerator,directed exactly at the second chamber. If the jet is low-power or curved, this is a sign of clogging of the atomizer, jets, valves of the accelerator pump. This problem is solved by cleaning them.

Air leak in intake manifold

Another reason why the engine does not develop speed may be a banal air leak in the intake manifold of the power unit. Symptoms of such a malfunction are difficult starting of the engine, its “triple”, problems with idling, an increase in fuel consumption and, of course, a loss in the number of revolutions. All this happens due to a sharp depletion of the mixture due to unaccounted for air entering the combustion chambers.

Most often, depressurization of the system occurs due to wear of the intake manifold gasket. It is rather difficult to determine that the injection engine does not develop speed precisely because of air leakage, just as it is not easy to find the place of depressurization itself. It is better to entrust it to specialists. But there are some things you can try to do yourself. You can, for example, take a syringe with a needle, fill it with gasoline (or solarium for diesel units) and treat with fuel the junction of the manifold with the engine around the perimeter. If the gasket between them has become unusable, then gasoline will be sucked into the combustion chambers along with air. If, after starting the engine, you notice positive changes in its operation, you can be sure that the reason lies precisely in the suction.

Wrong angleignition timing

It often happens that unlucky car owners, wondering why the engine does not develop speed, forget about the moment of ignition, although it is he who plays the most important role in the operation of the power unit. Timely ignition of the fuel mixture in the combustion chambers depends on it. If the ignition timing is set incorrectly, you will never, by any means and methods, achieve the coordinated operation of all engine systems and mechanisms.

In injection power units, the corresponding sensors are responsible for the correct moment. Their job is to collect information and transmit it to an electronic control unit, which in turn adjusts the angle. There are no such sensors in carbureted engines, so the ignition is set manually by scrolling the top of the ignition distributor.

Setting the correct angle on your own and without special equipment is not easy, although it is possible. At service stations, a special stroboscope is used for this, with the help of which a specialist determines the position of the mark on the crankshaft at a certain position of the distributor.

Violation of valve timing

Variation of the valve timing usually occurs when the timing belt breaks or when it is replaced. If you make a mistake in the form of a shift of at least one "tooth" between the gears of the crankshaft and the gas distribution mechanism, you will get a real problem in the form of unstable engine operation, increased fuel consumption, colored exhaust and other troubles.

In order not to get into a similar situation,work on replacing the timing belt and repairing all elements associated with it should be carried out at service stations. Well, if this is not possible, then it is necessary to carefully check and double-check the correspondence of the marks on the timing gears, crankshaft and flywheel.

Gaps between electrodes

Another reason why the engine revs slowly or not at all may be the wrong gap between the spark plug electrodes. I had a normal car with a normally working engine, but you didn’t like something, and you decided to change the candles, but you didn’t read the manufacturer’s recommendations. An error in the gap of one tenth or one hundredth of a millimeter will certainly make negative adjustments to the operation of the engine. Depending on its increase or decrease, this may be difficult starting, loss of traction, power loss, excessive fuel consumption, etc.

When it comes to clearances, two-stroke engines cannot be ignored. For them, candles are one of the most important elements that ensure the stable operation of the motor. So, if the two-stroke engine does not rev up, the first step is to check the condition of the electrodes and the gap is within the recommended values.

Clogged air and fuel filters

Needless to say once again that filters need to be changed every 7-10 thousand kilometers, and in special operating conditions twice as often. Contamination of these elements causes difficulties in supplying fuel or air to the manifold andcauses the engine to malfunction. The lack of normal fuel pressure in the fuel line causes a depletion of the combustible mixture, and if problems arise with the air supply, it is re-enriched. In both the first and second cases, the engine "suffocates", heats up excessively, loses power, speed, consumes more fuel.

Such a malfunction is eliminated by replacing the filter elements.

Sensor failure

Compared to the carburetor, the injection engine wins due to the fact that its operation is controlled by electronics, and if any problems arise, the driver will know about them by an error signal on the control panel. He will only have to connect the tester and read the code to determine which of the nodes is out of order. This happens thanks to electronic sensors that control the operation of the main systems and mechanisms. But they are not eternal either.

If any of them refuses to work, the engine goes into emergency mode. Due to the fact that the electronic unit ceases to receive the necessary information, the operation of the power unit becomes unstable.

Insufficient compression

And finally, the most unpleasant malfunction that leads to a decrease in speed and loss of engine power is insufficient compression. It is a consequence of the wear of parts of the piston group or the occurrence (coking) of the piston rings. As a result, the pressure in the combustion chambers decreases, and part of the energy from the combustion of the combustible mixtureis simply lost.

Compression is measured with a compression gauge. Its normal performance, depending on the type of engine, can vary from 10 to 14 kg/cm2. Having found a similar problem, you should think about overhauling the engine.