1. Connect a tachometer and a stroboscope to the engine. Start the engine and warm it up to normal operating temperature.
2. Disconnect the vacuum hose from the distributor and plug it.
3. Adjust engine idle speed according to regulations (see tables of sizes and adjustments at the end of the guide).
4. Using a strobe light, make sure that the pointer on the timing cover is aligned with the point on the crankshaft pulley scale corresponding to 3° (the price of one division of the scale is 5°- see accompanying illustration).
5. If necessary, correct the ignition timing by loosening the fixing bolt and turning the distributor housing accordingly.
6. Upon completion of the adjustment, tighten the distributor mounting bolt and, if necessary, correct the idle speed.
7. Connect the vacuum hose to the distributor and, using a stroboscope, make sure that the pointer has shifted to a point on the pulley scale corresponding to 15°. If such a displacement does not occur, then either the vacuum hose is blocked or the vacuum corrector unit is faulty.
8. Stop the engine and disconnect the diagnostic equipment.