Audi A4, S4

since 2000 release

Repair and operation of the car

Checks of a control system of ignition and injection

Address also to the Section Diagnostics of Malfunctions.

Components of a control system are very reliable. Malfunctions are, as a rule, connected with unreliability or pollution of contacts. Breakdowns of high-voltage wires most often arise because of pollution, humidity or damage of isolation, but not because of malfunction a component of system. Before drawing a conclusion on malfunction of any component, check its conducting.

To check operability of a high-voltage wire, having removed it from a candle and having approached to an engine surface (watching existence of a spark), it is impossible. You risk not only to receive blow current, but also to damage the control unit or the coil of ignition. If the engine works unstably, never remove tips of wires from candles for definition of the faulty.

The checks described below should be carried out if malfunction is obvious (refusal of a starter, admissions of ignition, etc.). Some malfunctions are less obvious and can not be shown because the control system of the engine switched in the emergency operation ignoring signals of separate sensors and using. Malfunctions of this sort are shown in increase of fuel consumption, instability of turns of idling, loss of power, a detonation, etc. If you found similar symptoms, address on HUNDRED.

The engine is not started

Keep in mind that at failure of the anti-theft device you will not be able to start the engine. Switch-off the device (address to the Head Governing bodies and methods of safe operation).

If the engine is not turned at inclusion of a starter or turned very slowly, check a starter and the battery. Attach the voltmeter to plugs of the battery and measure tension at an engine crankshaft provorachivaniye by a starter. Do not include a starter more, than for 10 seconds. If the voltmeter shows 9.5 Volts and less, be convinced of serviceability of the accumulator, a starter and system of charging (address to the Section of System of charging and start).

If at inclusion of a starter the engine rotates with a usual speed, but is not started, check all high-voltage components of system of ignition.

Following instructions of the manufacturer, connect a stroboscope and turn the engine crankshaft a starter. If the lamp on a stroboscope lights up, tension arrives on spark plugs. Be convinced of serviceability of candles. If the lamp is not lit, check high-voltage wires (address to the Section Check and replacement of spark plugs. Check of a condition of high-voltage wires).

If the spark is not present, be convinced of serviceability of the coil of ignition (or replace the coil on obviously serviceable or check resistance of windings). If malfunction is not found, look for it in other place. If after replacement of the coil the engine started being started — malfunction is found. Do not hurry to throw out the coil and to buy the new. Be convinced of reliability of accession of conducting to the coil (the engine could not be started because of the oxidized contact).

If the coil as it should be, it is faulty, possibly, the powerful buffer output cascade which is an engine control unit component, one of sensors of a control system of the engine or the accompanying knot. In this case in memory of the control unit the malfunction code which can be considered from memory has to be written down.

Codes of malfunctions can be considered by means of the special equipment.

Admissions of ignition

Most often unreliable contact of conducting with plugs of the coil of ignition or any sensor is the reason of admissions of ignition.

Switch off ignition and be convinced of reliability of connection of all sockets of system of ignition.

Check high-voltage wires. Be convinced that they are reliably fixed in points of promezhutochnykhkrepleniye and do not adjoin to metal parts of the engine. If the wire concerns metal and it damaged isolation, during the operation of the engine the spark will be given not on a candle, and on weight. At detection even insignificant damage of isolation at least of one wire replace all set.

It is possible to be convinced of full operability of wires, having temporarily replaced them with the obviously serviceable.

When replacing wires change them on one. It you will avoid risk of the wrong connection. Do not damage a wire at installation.

If high-voltage wires are completely serviceable, most likely, the coil of ignition or any spark plug is the reason of emergence of admissions of ignition. Establish a new set of candles (address to the Section Check and replacement of spark plugs. Check of a condition of high-voltage wires) or check the coil. The faulty or dirty sensor of position of the crankshaft can be the cause of emergence of admissions of ignition (address to the Section Functioning of a Control System and Injection of the Petrol Engine).

If check of above-mentioned knots did not lead to improvement of operation of the engine, consider codes of malfunctions from memory of the control unit (address to the Section Controller of Interface of the Personal Computer with onboard system of self-diagnostics of OBD II under protocols of the SAE standards (PWM and VPW) and ISO 9141-2 and Specifications).