If the ignition timing setting has been violated, check and, if necessary, adjust the ignition timing (see Checking the ignition timing).
To adjust the ignition timing for a specific fuel composition, an octane corrector scale is applied to the ignition distributor housing.
With a chisel on the tide of the block, we mark the middle of the scale - the zero position of the octane corrector.
With the engine warmed up to operating temperature, moving in IV gear at a constant speed of 50 km / h, sharply press the pedal «gas». If, at the same time, detonation (it sounds like the sound of valves) appears for a short time, 1–3 s – the ignition timing is correct. With prolonged detonation, the ignition timing is reduced by 1/2 division of the octane corrector scale, and in its absence, we increase it. We re-check in motion and, if necessary, continue the adjustment.