The situation when engine does not develop speed under loadIt's a car that's going idle, but if you hit the gas or go up, the traction goes off and the motor starts to choke, and it's not just discomfort, it's a direct signal that the power unit is in emergency mode or has a critical malfunction in one of the main life support systems.
The reasons for this behavior can be hidden anywhere: from a banal clogged air filter to serious problems with the air. fuel-frame In this article, we will go into detail about the mechanics of the process, explain why the motor loses power under load, and propose a step-by-step algorithm for finding a malfunction without wasting money on unnecessary parts.
Often drivers ignore the first symptoms, such as jerks during acceleration or increased fuel consumption, believing that the problem will disappear by itself. catalyst Understanding the nature of the problem is the first step to successfully restoring your vehicle to health.
Engine operation principle and nature of power loss
To understand why ICE If you don't pull, you have to remember the basic principle: the engine's power depends on the amount of fuel-air mixture that's burned, the electronics or the mechanical pump must be loaded with more fuel and air, and if one of the components of this chain fails, there's an imbalance. Turnover fall because the combustion energy is not enough to overcome the resistance of the transmission and inertia of the car.
The problem is often that the mixture is not proportionally proportional: if there is little air and a lot of fuel, the mixture is rich, the engine smokes and dies. If it is poor, the engine overheats and loses traction.ECU) try to compensate for these losses by adjusting the angle of ignition, but the reserves of the ECU are not unlimited.
⚠️ Warning: Prolonged operation of an engine with an improperly prepared mixture (especially poor) can cause pistons and valves to burn.
It's important to distinguish between power loss when idling and under load. If the engine roars at a neutral and gains 5000-6000 rpm, and when you go down a hill it barely drags 3000, then the mechanical part of the engine (compression, GRM) is probably intact, the problem lies in the intake, exhaust or fuel supply systems that do not keep up with the needs of the engine at a critical moment.
The main reason for the loss of revs under load is the inability of the intake or fuel supply system to provide the increased need for combustion resources for the engine.
Diagnostics of the fuel system: pressure and performance
The most common reason why the engine stalls or doesn't gain momentum when you push the gas pedal abruptly is because there's a shortage of fuel. The fuel pump can work properly at low speeds, but when the pressure on the ramp rises sharply, it's not enough performance. fuel-filterIt is a corny stuffed with dirt or paraffin (in diesel engines in winter).
Diagnosis should start with checking the pressure in the fuel ramp. You'll need a pressure gauge. You plug it in and compare it to your engine's data-sheet figures. Not only do you look at static pressure, but you also look at how fast it drops after you turn off the ignition. If the pressure drops instantly, it may be malfunctioning. fuel pressure or the pump's return valve.
And don't forget the nozzles. If they're contaminated or have the wrong spray torch, the fuel doesn't burn completely, and this is especially true for direct injection engines, where the requirements for fuel quality and nozzle condition are extremely high, and ultrasound cleaning or replacement can solve the choking problem.
Consider the main symptoms of fuel system malfunctions in the table below:
| Malfunction | A symptom. | Method of verification |
|---|---|---|
| Fuel filter is clogged. | Power drop at high speeds | Visual examination, replacement |
| Weak gas pump. | Failures at sharp acceleration | Pressure measurement in the ramp under load |
| Faulty RDT | Unstable idling, black smoke | Pressure measurement with vacuum tube |
| Dirty nozzles | Trotting, increased flow | Performance balance test |
Problems with air supply and intake tract
The engine is basically an air pump, and if it can't breathe in the right amount of air, no fuel can help it. air-filterIt's banal, but the fact is that a filter clogged with dust or foliage creates a vacuum that simply "strangles" the engine at high revs.
The second important element is the air mass flow sensor (DMRV or MAFIf it's lying and it's understated, the engine's brains will make a poor mixture, and under load the engine will be sluggish. Try to throw off the DMRI chip: if the engine's performance has improved or hasn't changed, the sensor is likely to malfunction and need to be replaced.
When diagnosing DMRV on a heated engine, the voltage on the signal wire when ignition is turned on (the engine is stopped) should be about 0.996 V. If more than 1.05 V, the sensor requires replacement.
It's also worth checking the intake manifold for the sucking of unaccounted air. Cracks in the pipes, worn-out gaskets or vacuum hoses let in excess air after the sensor. This disrupts mixing. listen for characteristic hissing sounds or use a smoke machine to find leaks. This is especially common on high-mileage engines where the plastic dries.
Another hidden enemy is the throttle, which can interfere with proper closure or opening, and can disrupt the channel's patency at shallow opening angles. Regular cleaning of the knot with adaptation through a diagnostic scanner often returns the car to its frolic.
Emission system and catalyst
One of the most insidious reasons why a car doesn’t go is a clogged catalyst or particulate filter.DPF/FAP) The combustion products must be free to exit the cylinders. If the exhaust tract is blocked, there is high back pressure. The piston group simply cannot push the gases out, and no new batch of the mixture enters the cylinders.
You can diagnose this problem by twisting the lambda probe in front of the catalyst and starting the engine. If thrust comes, then the exhaust path is free. If not, the problem is elsewhere. Also, the clogged catalyst is the whistling sound from under the bottom when you try to accelerate sharply and the smell of rotten eggs.
⚠️ Attention: Unflashing the catalyst without flashing the ECU (Euro-2) will cause the Check Engine lamp to burn constantly and the engine to malfunction.
On diesel cars with a particulate filter, the problem may be the regeneration system, if the car is only operated at short distances, the filter does not have time to burn soot and clogs, in which case forced regeneration through service software or a replacement of the filter is required.
Why is the catalyst clogged?
The catalyst often fails due to the ingestion of unburned fuel (with faulty candles or injectors) or the use of leaded gasoline. The ceramic base is melted and converted into a monolith, completely covering the exhaust.
Electronics, sensors and ignition advance angle
The modern engine is completely dependent on the readings of the sensors. DPC The snags fail when you're heating or vibrating, and the sparks can disappear when you're loading, and the camshaft position sensors also act, and these sensors often don't immediately light up on the dashboard, but they do affect the engine.
The knock sensor is another important player. If there's a malfunction or a big knock in the engine, the ECU goes into emergency mode, locking the angle of the ignition as much as possible. The car becomes "vegetable", the flow increases, and the dynamics drops. Checking is done through the oscilloscope or by replacing the sensor.
It is also worth mentioning the system. EGR If the EGR valve is jammed in the open position, the engine is constantly pressed by its own exhaust gases. On idles, this may not be noticeable, but under load, the oxygen content in the intake drops to critical values, and the engine stops pulling.
☑️ Primary electronic diagnostics
Mechanical malfunctions of the engine and transmission
The mechanics are not to be discounted. The reduction of compression in one or more cylinders due to the lagging rings or the failure of the valve will lead to loss of power. The engine will work unevenly, and under the load the lapses will become obvious. The measurement of compression is a mandatory procedure if other methods have not worked.
And it may not be the engine, it may be the transmission. GDT (hydrotransformer) on the automatic or the clutch on the mechanics will create the illusion of a weak motor. The turn is growing, the car is not accelerating. Check the oil level in the automatic transmission and the state of the clutch.
The timing phases are another critical parameter: if the timing belt jumps on the tooth or stretches, the phases will go wrong. The engine will work, but it is extremely inefficient. On modern phase-rotor engines (Phase-rotor engines).VVT-i, VANOS) problems with the oil pressure or phase rotor solenoids also cause loss of traction at certain speeds.
If the compression is normal, the fuel pressure is fine, and the catalyst is not clogged - look for a problem in the jumping of the timing belt or the failure of the phase rotors.
Frequently Asked Questions (FAQ)
Why does the engine stop when you press the gas pedal sharply?
This is often a sign of a poor mixture at the time of acceleration, and the culprit may be a dying gas pump that can not raise the pressure, or a heavily contaminated fuel filter, and it may also be possible to suck air in the intake manifold.
Could the lambda probe be the cause of power loss?
Yes, if the lambda probe is lying to a rich mixture, the ECU will try to deplete the mixture, which will lead to failures. If the probe dies completely, the ECU will switch to the emergency table, which will also limit power and increase consumption.
How to quickly check if the catalyst is clogged without removing?
The easiest way is to unscrew the first lambda probe (to the catalyst) and try to drive through, and if the dynamics improve, then the catalyst creates resistance, and you can also measure the pressure of the exhaust gases with a manometer through the lambda hole.
Does the quality of spark plugs affect traction under load?
Old candles with a large gap or a high load can give a slight spark, the single spark will break, and under load (when the pressure in the cylinder is high) will break the insulator or spark will break the stream, causing tripping and loss of power.