miss fire F150 4.6 1997

[6arrows]

My son has a 1997 F150 4.6 windsor 133thousand with a miss fire Changed the plugs they were shot also new wires still a miss fire. there is two coil packs up front they are motocraft im not sure if they are 1997 or have been change. a small store up here says to pull 2 coil wires off and if no spark jumping back and fourth there bad well i did that and on both coils i saw no jumping spark. should i just buy 2 new coil pks. thanks for the help

[Jeremy airjer W]

Is the check engine light on?

When you pulled he wires off did you completely remove them from the coil or did you hold them about a half inch away from the coil so you could see if there was spark jumping from the coil the the wire?

[6arrows]

yes check engine light on code p307 cylinder missfire only code. when i take one wire off at time and hold half inch away i see a spark. But if i take two wires off at a time and keep out of way no spark jumping back and fourth on coil? Thank for help

[6arrows]

The wires on it are autolight could that be the problem

[Jeremy airjer W]

What about if you pull the number 7 plug wire off of the plug. Can you hear a really solid snap of spark?

[Jeremy airjer W]

I should also ask can you physically feel the misfire?

If so and you have good spark than maybe its time to check compression in that cylinder. If compression is good I would do an injector balance test to make sure that injector is working.

[Scott K]

Old school spark test, hold the plug wire at the end with your right hand, left hand on the top of the metal engine. If you just swear, you have weak spark, if you jump, hit your head on the hood, and smack your elbow on the hood, then swear, it is good spark.

This works best if done in front of friends, and when possible, one of them with a video camera

[Jeremy airjer W]

Do not try this if you are over 65, have a heart condition, or talking cialis!

[Scott K]

[6arrows]

Jermey you can feel it a little bit at iddle but when you get up past 2nd gear it runs pretty well. when doing a compression test do i just take out number 7 plug and put gauge in cylinder num 7 and spin truck over. do you think i should change them coil packs im thinking they might be factory coil packs? thank for info also

[Jeremy airjer W]

I think it would be good to do a couple of tests to see if you can narrow down the possibilities befo you start replacing more expensive parts.

You are correct on the compression test. Remember to disable the ignition or fuel system to keep the car from starting. Hold the throttle wide open. Allow the engine to crank over three full revolutions. Keep everything uniform (if you check a cylinder with the plugs in all the other cylinders replace the plug in the cylinder you checked before checking the next cylinder.

An adjustable gad spark tester might shed some light on the subject.

[6arrows]

Sorry for long delay Jeremy iv been trying to hunt and work on this thing compression checked out good. I did find that the egr tube going to manifold is broke off fixing that today.With a spark tester should i pull off spark plug wires one at a time and check spark.If no spark can i use it to check spark on the packs also. would i put tester right in plug on coilpack Thank you for your information.

[6arrows]

And if it does come back to being coil packs should i get the more expensive ones from a store or can i get the cheaper ones off line?

[Jeremy airjer W]

With a spark tester should i pull off spark plug wires one at a time and check spark.If no spark can i use it to check spark on the packs also. would i put tester right in plug on coilpack Thank you for your information.

Yup.