God, what a bummer. Look, that's either because it's not connected to the correct wire or because the clock isn't designed for four-cylinder engines.
Normally, in four-cylinder engines, there are two sparks per crankshaft revolution, except for DIS electronic ignitions which operate with wasted spark. This means two sparks fire simultaneously in cylinders 1 and 4, and another two in the next half revolution in cylinders 2 and 3.
These systems are characterized by having two square black ignition coils on the left side of the cylinder head (e.g., Opel Astra F 1.4)
instead of the traditional distributor, which has a separate ignition coil bolted to the chassis and connected by the high-voltage wire and the power and ground wires.
In the case of DIS ignition, each coil has a four-pin connector that receives HALF THE PULSES OF THE ENGINE (that's why it has two coils).
If your tachometer doesn't have pulse calibration, you'd have to buy one that does or one suitable for an eight-cylinder engine. (You'd have to look at tuning or racing parts, or buy it online from the USA.)
In any case, I'd have to see the car to be 100% sure about what I've told you.
Best regards.
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Sep 14, 2025