Thanks ALain,

actually, my car can "drink" gasoline, alcohol or both, mixed. The car´s ECU control the correct amount of fuel.

My car has 4 cylinder and 4 injectors (1 injector for each cylinder). Should I measure the "on-state" for each cylinder ?

I´m counting pulses from the speed sensor using Timer 0 (as a 250ms timer) and Timer 1 as a tick counter.

Can I use the CCP module (to measure the on-state time) without my timers stop working ?

When I built my first digital speedometer/hodometer/termometer for my old opel corsa, I had a perfect signal from my speed sensor : When the car was stoped, I have no pulses. When the car start moving, I had 8 pulses / turn.
But now, I don´t know why, when I start my new opel´s engine, the hall sensor start to send me 2 pulses/sec with the car stoped. When I start moving, it gives me to 10 pulses / Sec.

I have built myself a new speed sensor with a hall-effect sensor inside a rigid plastic capsule. This solution gives me 8 pulses/second (8 small magnets were fixed close to the sensor. It was a really hard work...

I´m still thinking on how to fix the problem on my original speed sensor. As I´m making 4 Timer1 readings / second I will have to work arround this problem envolving the "false" pulses.

Anyway...I did really appreciate your reply ! ! !

Regards !

Sérgio