The same thing that causes them on on all cars.. faulty spark plug/wire. Sometimes you might get a bad coil pack. cross your fingers and hope it's not the case as they get costly..
yes
All Crown Vics are V8s
2 ( 1 camshaft for each cylinder head )
the gas line from the tank might have trash in it the gas line from the tank might have trash in it
FUseable link or corrisio on the wires
Gets clogged
This may not be the answer you're willing to hear, but the problem could be from a blown head gasket. I had the same problem on my 85 Crown Vic after hitting on it a little bit too hard after it sat for about three years. A blown head gasket would be my best guess in this situation. In that case, the entire engine will have to be disassembled and rebuilt from the cylinder heads UP.
try changing the spark plugs
you have to replace your spark plug wires there is a coil on each wire for each cylinder.
FIREWALL 4 - 8 3 - 7 2 - 6 1 - 5 FRONT
Cylinder 8 is driver's side, closest to the rear of the vehicle. You can find this stuff for free at Autozone.com under specifications, firing order.
It could be the relay