Cam sensor...

its for fueling, basicly to give an accurate position and timing for when to squirt the fuel

somebody will be along soon to give a link and a better explention

Interesting that one...happened to my girlfriends focus too. Does anyone know why it fails since nothing moves in it. Is it reduced sensitivity, faulty wiring caused because its on the engine and the engine moves or what?

Worst thing was it was intermittant sometimes the car would start and run Ok and the next it would just turn over but not fire.

M...

Indeed- the CPS is there to correctly time the sequential mode injection. With no signal present, the ECU will run in batch fire mode where all injectors operate together- twice per engine revolution.

In sequential mode injectors fire singlely just before the induction stroke on each cylinder upto 4500rpm and / or 80% throttle.

After this they switch to dual sequential and fire twice per stroke per cylinder, once on the exhaust stroke, and once just as the intake valve opens and draws air / fuel into the cylinder. This is mainly to ensure enough fuel is present to meet demand.

(this is correct for most Ford EEC5 ecu's.)

Tim..