causes very poor gas mileage
yes
If it is malfunctioning it can affect fuel mileage.
yes
YES YESYESYESYESYESYESYES
poor gas mileage
Yes.Yes.
almost any malfunction in your car can cause a drop in gas mileage (including the cam sensor) any time when your engine has to try harder to do what it is meant to do or is confused, and has to guess, due to a bad sensor it can cause poor mileage, and even further damage to your vehicle ex: a bad cam sensor can also make starting your car take longer possibly damaging your starter.
Check ingine light and your gas mileage get worse.
bad gas mileage
Bad idle, hesitation on acceleration, DEcreased performance and gas mileage.
did it change for the better or worse? if it changed for the better it could of been bad.