I am working on a motorcycle diagnostic tool. Everything works fine except for the fact that when the engine is turned on, in some motorcycles spikes start appearing all over the circuit, and the device LCD malfunctions. How can I filter this noise before it reaches the device's powersupply?
Here are two samples of the noise that I am receiving using an oscilloscope The peak voltage is probably higher and can't be seen due to oscilloscope limits:
I used an LC filter on the input of the power supply. It was fine when I simulated the circuit, but when I tested it on the device it made no difference.
simulate this circuit – Schematic created using CircuitLab
I also used 5V TVS diodes in the circuit, after the device regulator but I'm getting the same noise all over the circuit. Any advice on how to remove the spark plug noise?