First please note at the time of detonation. If this effect had not previously existed, it can occur after refueling low-quality gasoline, in violation of the adjustment of the ignition or after long periods of operation of the motor at low capacity.
Secondly, check how the engine reacts to load changes. Most often, detonation occurs at low rpm at maximum load in engines with low compression ratio, and at maximum power with the appropriate load rpm in engines with high compression ratio. In the first case, the detonation should dramatically increase as the load increases at low rpm. In the second case, the detonation dramatically increase when moving at submaximal speeds.
Feature momentary detonation from the long-term. If you only heard 3-4 knock, do not pay attention to this phenomenon. In this case, the effect of detonation carries more positive impact on the engine than negative.
Pay attention to the color of exhaust gases. The presence of black or greenish haze points to a recent knock, even if you do not hear the characteristic knocking. This smoke originates from the collapsing of the aluminum piston and said about the critical levels of detonation and need to replace pistons and piston rings.
If the detonation was discovered after another tank of gasoline the respective brand, do not rush to adjust the ignition. The reason for the detonation may be a layer of carbon on parts of the combustion chamber. Ride 20-30 minutes. If detonation persists, start to gradually reduce the ignition timing. After some time, if necessary, continue to reduce the size of the angle to the complete cessation of detonation. If detonation effect will handle it does not work, look for the cause of strange sounds in malfunction of components and mechanisms of the engine.
An effect similar to a detonation may occur when the ignition is turned off. This engine, despite the lack of spark from the spark continues for some time to twitch. In fact, this effect has nothing to do with detonation and is called desalinho. The reasons of this effect associated with the use of low octane fuel and is more typical for new engines, the actual compression ratio which is higher than that recorded in the passport.
Advice 2 : How to check the knock sensor VAZ
On cars VAZ are set two types of knock sensors: one-touch and two-pin. In the diagnosis of this sensor, see the precautions in the repair of this system.
You will need
- - multimeter (tester);
- - Allen wrench
Please note: the car access to the knock sensor complicates the intake module. As a result, remove the knock sensor to the touch. To facilitate the process, remove the splash shield of the engine and remove the sensor, get close to him from the bottom of the car (on a viewing hole or overpass).
For removing the knock sensor Unscrew the Allen key sensor retaining bolt from the cylinder block. Remove the sensor from the mounting studs and remove it from under the intake module. Disconnect the harness connector from the sensor by pressing the locking button.
To test the sensor, connect its findings multimeter included in the mode voltmeter with a measuring range up to 200 mV. For a proper connection, one-touch sensor to the device, the negative lead (black) connect the device with the weight sensor (installation location of the bolt). The positive wire (red) connect signal wire located in the connector of the sensor. Two-pin sensors, connect both pins to the wires of the tester with the correct polarity.
Then with a screwdriver lightly tap on the sensor body, mimicking the detonation. The tester should show voltage spikes size 40-200 mV depending on the force of the concussion. If any malfunction of the sensor reaction to the shock will not. The sensor should be replaced. Remember that in some cases, the devices are not able to detect a weak signal and Vollmer will malfunction the sensor.
Set the tester mode to measure resistance and connect it to the terminals of the sensor. It is desirable that the device had the ability to measure an infinitely large resistance. Defective knock sensor on the car must have very high resistance tending to infinity.
A more accurate test of the knock sensor is only possible on a special stand. Proven sensor install in the reverse order. Mounting bolt tighten to 20-25 Nm.