Engine Controls - Basic Diagnostic Procedures: Diagnosis BMW Z3 E36 рестайлинг

VISUAL INSPECTION

Visually inspect all electrical wiring, looking for chafed, stretched, cut or pinched wiring. Ensure electrical connectors fit tightly and are not corroded. Ensure vacuum hoses are properly routed and are not pinched or cut. Inspect air induction system for possible vacuum leaks.

Oscilloscope Pattern Diagnostics

1. Evaluate sparking period and ignition voltage peaks at idle. Voltage peak No. 1 indicates normal combustion period. Voltage peak No. 2 indicates normal ignition voltage peak. Ignition system is okay. (Scheme 1)
2. If scope indicates a long sparking period (voltage peak No. 1) with ignition voltage (voltage peak No. 2), low compression is present. If sparking period is fluctuating, spark plug is fouled. (Scheme 2)
3. A short sparking period (voltage peak No. 1) with high ignition voltage peak (voltage peak No. 2) or a constant but short sparking period, indicates a defective ignition lead. (Scheme 3)
4. During evaluation of ignition voltage peaks and attenuation process at idle, if scope indicates a beginning of attenuation process with normal peaks upwards and downwards (voltage peak No. 1), or attenuation process is greatly shortened (voltage peak No. 2), ignition coil is defective. If there is an absence of initial downwards attenuation (voltage peak No. 3), ignition coil is defective. (Scheme 4)
5. During evaluation of sparking voltage at idle, normal combustion period is indicated by voltage peak No. 1. Normal attenuations to sparking voltage line is indicated by voltage peak No. 2. Ignition coil is okay. (Scheme 5) If shorter sparking period is indicated (voltage peak No. 1) or attenuation to sparking voltage line is only slight (voltage peak No. 2), ignition coil is defective. (Scheme 6) If sparking period is much shorter (voltage peak No. 1) or attenuation to sparking voltage line is absent (voltage peak No. 2), ignition coil is defective. (Scheme 7) If there is no sparking voltage line, ignition coil is defective. (Scheme 8)
6. During evaluation of combustion voltage line at a raised engine speed, voltage peak No. 1 indicates normal combustion period. Voltage peak No. 2 indicates normal attenuations to sparking voltage line. Ignition coil is okay. (Scheme 9) A shorter sparking period (voltage peak No. 1) and if attenuations to sparking voltage line is only slight (voltage peak No. 2), then ignition coil is defective. (Scheme 10) If combustion period (voltage peak No. 1) is normal or attenuations to sparking voltage line are absent (voltage peak No. 2), ignition coil is defective. (Scheme 11)

Scheme 1

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Scheme 6

Scheme 7

Scheme 8

Scheme 9

Scheme 10

Scheme 11

Oscilloscope Pattern Diagnostics (Various Coil Manufacturers)

If vehicle is equipped with Bremi, Beru, May and Christe or Bosch coil, evaluate ignition voltage peaks and decay characteristics at idle speed. (Scheme 12) To evaluate combustion voltage characteristics at increased engine speeds of approximately 2500 RPM (Scheme 13)- (Scheme 16).

Scheme 12

Scheme 13

Scheme 14

Scheme 15

Scheme 16

Scheme 17

Scheme 18

Scheme 19

Scheme 20

1. For evaluation of sparking period at idle, voltage peak No. 1 indicates normal ignition voltage peak. Spark plug is okay. If ignition voltage peak (voltage peak No. 2) is low, electrode gap is small. If ignition voltage peak (voltage peak No. 3) is high, electrode gap is too large. (Scheme 17)
2. For normal combustion and spark plug (Scheme 18) If combustion period is long, electrode gap is small. (Scheme 19) If spark period is short, electrode gap is large. (Scheme 20)

See also:
• RELAYS
• WIRING DIAGRAMS
• ON-VEHICLE ADJUSTMENTS