IGNITION COIL/WIRING/ECU AILMENTS

摘要

This Focus employs a 'wasted spark' ignition system, in which cylinders 1 and 4 are paired, as are cylinders 2 and 3. Since the cylinders are paired in this way, a problem with one cylinder in the pair also affects the 'opposite' cylinder with which it is connected via the coil. It can happen that the car randomly loses 50% of normal power (the misfiring is VERY noticeable), and at the same time the management warning lamp will flash. A fault code will be stored, relating to 'Coil Primary Circuit'. In normal operation, the coil is switched by the ECU, but the ECU can be at fault in not triggering the coil as designed. Alternatively, the coil itself can fail. Dean recalls that the first-generation Focus models were particularly prone to ECU failures, causing the symptoms described, and also notes that later models under review are not immune. He advises that it is always wise to renew the coil at the same time as the ECU is repaired or changed.