Check the Vehicle Emission Control Information ( VECI ) decal located in the
front of the engine compartment ( it will show what type of spark plugs to use
and the spark plug gap )
you need to refraise this question as you cannot have a V6 straight engine either you have a V6, or you have a straight 6
its to the rear of engine under the intake manifold
www.motorcraft.com shows (.044 inch ) plug gap on the 1989 F150 300 cubic inch ( 4.9 L ) straight 6 cylinder engine
V8 firewall 4 - 8 3 - 7 2 - 6 1 - 5 front Straight 6 cylinder , 1 to 6 , front to rear
( .054 inch ) for the 5.0 L - V8 engine and ( .044 inch ) for the 5.8 L - V8 engine ( Helpfull )
If the check engine light is flashing with the engine running , that means a spark plug misfire has been detected
.044 inch according to www.motorcraft.com for the 4.9 L ( 300 cubic inch ) straight 6
Check the Vehicle Emission Control Information ( VECI ) decal located in the front of the engine compartment ( it will show the type of spark plugs to use and the spark plug gap )
Which engine?
The spark plug firing order for your 1996 F-150 - 4.9 L - straight six cylinder is : ( 1 - 5 - 3 - 6 - 2 - 4 ) The distributor rotor turns CLOCKWISE The distributor cap is installed with the marked # 1 position facing AWAY from the engine The engine cylinders / spark plugs are numbered 1 through 6 from front to rear
.044 inch ( for your 4.9 liter / 300 cubic inch straight 6 cylinder engine in a 1991 Ford truck , according to motorcraft.com )
I don't know if it's the same as the (1996 ) Ford F-150 straight six but that is ( 6 quarts with engine oil filter change )