The situation when you press the gas pedal, the engine begins to roar, the tachometer arrow confidently crawls up, but the car either does not accelerate at all, or accelerates extremely sluggishly, always causes panic. This phenomenon motorists often call the “slipper” transmission, although in fact there can be many reasons, and not all of them are hidden in the gearbox. It is important to understand that at this point, the energy of combustion of fuel is wasted, not transferred to the wheels, which can lead to serious breakdowns if you continue operation.
Ignoring such symptoms is fraught not only to get stuck on the sidelines, but also to get a bill for expensive repairs of units. Critical wear and tear The nodes occur at times when the system is operating in emergency mode. In this article, we will discuss the mechanics of the process in detail, divide problems into groups for mechanical and automatic boxes, and also touch on the issues of engine operation.
The first thing to do when a driver detects such a malfunction is to stop aggressively pressing the gas. Further attempts to “unwind” the engine can finish off the already affected frictions or lead to overheating of the oil. Let’s see where the connection between the motor and the wheels was broken.
⚠️ Warning: If you smell smoke or see smoke coming from under the hood during the drive, stop immediately in a safe place and turn off the engine. Continuing to drive with a slipping transmission can cause fire.
Problems with clutch on the mechanical box
The most common cause of the described problem on cars with ICSW - that's the wear of the clutch disc. The torque transmission mechanism is arranged so that the disc is pressed against the flywheel by the clutch basket. When the friction pads are worn, the friction force drops and the disc begins to slip relative to the flywheel. Visually, it looks like an increase in engine speed without a corresponding increase in the speed of the car.
Diagnosing wear can be quite simple. Try tightening the hand, turning on the third or fourth gear and smoothly release the clutch, adding gas. If the engine does not stop immediately, but begins to “choke” or stalls with a great delay – the clutch requires replacement. Also, the sign is a “heavy” pedal movement or, conversely, too free movement.
However, it is not always the disc itself that is to blame. The problem may lie in the squeezable bearing or in the surface state of the flywheel. If the flywheel has cracked or it has overheated ("lead"), even a new clutch disc will not be able to provide reliable contact. In such cases, a flow or replacement of the flywheel is required.
- 🔺 Erased friction linings of the clutch disc are natural wear.
- 🔺 The hit of oil on the disk due to the crankshaft or primary shaft of the gearbox.
- 🔺 Deformation of the clutch basket petals or weakening of the springs.
- 🔺 Incorrect adjustment of the cable or hydraulic actuator of the clutch disengagement.
⚠️ Attention: Getting oil on the friction clutch linings often requires not only replacing the oede, but also thoroughly washing all parts with a degreaser, otherwise the new clutch will also quickly fail.
Failures of automatic transmission (ACP, CVT, DSG)
Owners of cars with machine-gun face a similar problem at least, but the reasons here lie in the hydraulic transformer or friction packets. In classical hydromechanical automatic transmissions, the pressure of oil is responsible for the transmission of force. If the ATF fluid level is critically low or the pump does not create the right pressure, the frictions do not shrink with sufficient force and begin to slip.
Variants require special attention (CVT). In them, a belt or chain transmits force through cones. If the belt is worn or stretched, it begins to slip down the pulleys. This is accompanied by a characteristic howling sound and a sharp increase in turnovers. Operation of the variator with slipping kills pulleys and belt in a matter of kilometers.
Robotic boxes (art.DSG, PowerShift) are structurally close to the mechanics and their grip wears out as well. However, robots often have the problem of incorrect adaptation or malfunction of the mechatronic. The control unit may simply “not understand” that you need to close the disks tighter, and keeps them in a semi-open state.
Why can't you tow on a machine?
Prolonged slippage in place (for example, getting stuck in snow) leads to instant overheating of oil in the automatic transmission. The hydrotransformer at this point works as a powerful stirrer, heating the liquid to temperatures at which it loses its properties and burns.
Diagnosing automatic boxes is complex and requires a scanner to be connected. Errors can indicate solenoids, pressure sensors, or oil temperature. Often before the pressure drop, the hydroblock is contaminated with friction wear products.
Fuel system and air supply
Sometimes the problem lies not in the transmission, but in the fact that the engine simply cannot develop power, although the speed increases. This happens when the balance of the fuel mixture is disturbed. If too much air or too little fuel is supplied to the cylinders, combustion is inefficient. The car does not pull, creating the illusion of slipping, although the clutch is serviceable.
Clogged. fuel-filter or a dying gas pump cannot supply the right amount of fuel under pressure when a throttle is opened abruptly. Turnovers grow inertially, but there is no thrust. A similar situation occurs with severe contamination of nozzles or a malfunction of the fuel pressure regulator.
From the air side, a clogged air filter or a faulty mass air flow sensor causes problems (DMRV). If the car’s brains get the wrong amount of air, they make the wrong mix. The engine starts to “trick” or work unstable.
| Symptoms. | Probable cause | Method of verification |
|---|---|---|
| Spread-up jerks | Fuel filter is clogged. | Replacement of the filter |
| Floating speeds | Air suction or DMR | Computer diagnostics |
| It's dead on the move. | pump or pressure regulator | Pressure measurement at the ramp |
| Black smoke from the exhaust | Re-enrichment of the mixture | Candle and lambda check |
Check the condition of the air filter before a thorough engine diagnosis. In 15% of cases, it is the forgotten old filter that causes loss of dynamics and increased fuel consumption.
Problems with the exhaust system and catalyst
Few people realize that the engine can choke from its own exhaust gases. If catalytic converter clogged with combustion products or destroyed, gases cannot freely escape from cylinders. The engine spends a lot of energy pushing the exhaust out instead of turning the wheels.
In this state, the car can accelerate only to a certain speed (for example, 60-80 km / h), after which further acceleration becomes impossible, although the speed continues to grow. Often this is accompanied by a hum from under the bottom and loss of reception at low revs.
Diagnose the clogged catalyst can be by twisting the lambda probe in front of it and starting the engine. If the dynamics improves dramatically, the exhaust system requires intervention. The pressure of the exhaust gases can also be measured with a manometer.
Electronic restrictions and protection regimes
Modern cars are equipped with many safety systems. If the engine control unit (E)EBOU) fixes a critical error, it can put the car in emergency mode (Limp Home Mode). In this mode, the power is artificially limited to reach the service. The surge may increase, but the ECU simply shuts off the fuel supply or throttle.
It is also worth checking the work of the accelerator pedal. In electronic pedals (E-Gas) no cable, the signal is transmitted by a potentiometer. If one of the tracks of the potentiometer has worn off, the computer may not see the full pedal pressing, even if you pressed it into the floor.
☑️ Primary Diagnosis of Power Loss
⚠️ Warning: Resetting errors in emergency mode without eliminating the cause is useless and dangerous. The system will again limit power once the parameters go beyond the permissible limits, which can happen at the time of overtaking.
Diagnosis and elimination methods
The search for faults should begin with the simplest and cheapest. First, check the levels of technical fluids and the condition of the filters. Then we move on to computer diagnostics, which can immediately indicate ignition gaps or sensor problems. Only after eliminating problems with the engine makes sense to climb into the transmission.
For mechanics, adjustment or replacement of the clutch kit is often enough. For machines, the procedure is more complicated: you may need to change the oil, repair the hydraulic unit or complete bulkheading of the box. In the case of variators, sometimes only replacing the entire node helps, since repairing pulleys is economically impractical.
Do not forget about the banal things: check whether the handrail cable is attached to the rear calipers or whether the guide of the brake mechanism is jammed. Constant braking by one of the wheels will create the feeling that the car is not going, although the problem is the brakes.
The main conclusion: the growth of speed without acceleration is always a break in the connection between the engine and the wheels (clutch, automatic transmission) or the inability of the engine to develop power (fuel, air, exhaust).
Can I get to the service if the turnover grows, and the car does not go?
You can only get there if the car is moving at least somehow and you are sure that it is not brakes. However, the distance should be minimal (several kilometers), and the style of driving should be as gentle as possible. If it is an automatic machine or a variator, the risk of finishing the box to the state of “metal shavings” is very high. Better call a tow truck.
Why did the problem persist after the clutch replacement?
There may be several reasons: poor-quality spare parts (a new disc can be defective), a flywheel is not leaked (surface beating), a faulty squeezing bearing or the problem is not at all in the clutch, but in a two-mass flywheel, which requires replacement along with the set.
How often should I change the oil in the automatic transmission to avoid problems?
Manufacturers often write "for the entire life", but the reality is that the oil loses its properties every 60-80 thousand km. Regular partial or complete oil replacement DISTRIBUTION significantly prolongs the life of frictions and hydroblock, preventing slippage.
Does the quality of gasoline affect this problem?
Yes, bad gasoline with low octane or impurities causes detonation. The ECU hears the knock and adjusts the angle of ignition, which causes the power to fall. The car stops pulling, creating the effect of "cotton" acceleration, although the speed can grow.