87 f150 with 300 straight 6. Plugs and wires haven't been changed in probably 10 years. Truck was running ok but i thought it was about time for them and i thought maybe it would help the power and fuel milage a little. Changed the plugs, wires and distributor cap. Now it's missing. Idles fine but when i hit a hill or hard pull it jumps, spits and sputters. Any help??? I'm certainly no mechanic so any advice would be great.

 

From what I can remember about those engines they were pretty good if maintained.
Kinda like everything else.
When you replaced the spark plugs did you set them to the proper gap?
Did you replace the plug wires one by one or did you just pull them out and start from anywhere? Check that the rotor is all the way down on the dist shaft if you removed it .

 

gapped them to .044 per Haynes Manual. Changed the wires one at time to make sure I got the firing sequence correct. I didn't change the rotor just the cap. Thats why I cant figure out what's gone wrong. Everything should be back as it was.

 

Things happen. It might be a good idea to change the fuel filter. If that doesn't help , you might have a coil that is breaking down under load.

 

fuel filteer isnt it, make sure all the wires are right from your hanes manuel then check again, and again, make sure all the plugs are pushed in all the way to.

 

And make sure the wires are all on tight.

 

Is the firing order right (1-5-36-2-4?) I was always and forever screwing that up. Also, as the plugs have just been replaced, pull them back out and check them. Sometimes they are put back on the shelf after being dropped and crack, causing this very problem.

 

Firing order info:

http://www.ford-trucks.com/forums/13...ing-order.html

 

If you haven't solved your problem yet, consider doing this.
Remove the # 1 spark plug,the one closest to the fan.
Remove the distributor cap.
Have someone crank the engine while you observe the direction the rotor turns then keep tapping the start position with the key switch until you feel the pressure coming up from the # 1 plug hole. Stop there and continue turning the engine in the same direction by hand using the alt pulley or whichever one is easiest to turn . Watch for the TDC (top dead center) mark on the crankshaft pulley and line that mark up with the pointer located just behind the pulley. That should get your rotor pointing to # 1 cylinder on the dist cap when in place. Then check to make sure the plug wire at that position goes to #1 cyl.
Continue from there with the firing order given, 153624 going in the same direction on the cap as the rotor turned. You cannot always go by the #1 marked on the cap since someone could have removed the distributor and placed the shaft a few teeth off. with that done as described the engine should start and run fairly well until you can set the timing more precisely with a timing light. If it still runs poorly , As greasemark stated recheck the plugs one or more could have been damaged especially if tightened too much or the socket not being kept straight when tightening the plugs. Last , but not least make sure the wires are pushed all the way down on the plugs and also in the towers of the cap as previously suggested.
If the cap was tightened too much it could have a crack in it that could cause the same symptoms.
If you still have the same problems after all that checking, that you did correctly, let us know.