cylinder 4 misfire mystery/possibilities

[randyj68]

Hello.....hoping to get some input. I bought a 98 expedition the other day.. has some miles on it but is clean and ran like a champ, 4x4 worked great and so on. On the way home it started skipping/missing. Just before getting home the check engine light comes on and the scanner shows a cylinder 4 misfire. Plug wires look almost new....can only assume the plugs are fairly new. I took the ground cable off today, checked the connection with the wires to the plugs and wires to coil along with the fuel injector plugs. Hooked the ground cable back up started it and its still skipping/missing. Took off around the neighborhood and it actually smoothed out.....engine light not on. Any suggestions

 

[FordandPolaris]

I would guess that if anything, the plugs are new and the coils are old. I have had multiple bad misfire conditions across three different Expeditions in my family appear. We have both the 5.4 and 4.6, and every time a new coil and spark plug has made it go away. I would start with that and then trouble shoot from there. Cylinder 4 is the one in the very back on the passenger side unfortunately.

Just to save on guess work, the small bolt is a 7mm and the spark plugs are 5/8. Buy some swivels and extensions if you don't already own some...

 

[richinspirit]

Not sure if this would apply to you, but the very inexpensive COP boot that seals the spark-plug well from water and debris can begin to leak and allow that spark-plug well to gather water/gunk.

This was a very inexpensive fix for a previous modular (nickname for the 4.6/5.4 in these Expeditions) motor misfire I had. Cost me $5 back in the day and some dielectric grease to clean the COP->plug connection but cured an intermittent misfire condition.

 

[Bedrck47]

which engine does the 98 have 4.6 or 5.4

 

[FordandPolaris]

Both... Not to insult you but if you're unsure which motor is in your truck, changing the closest spark plug to the firewall might be worth the couple hundred bucks at the mechanic...

 

[Bedrck47]

FordandPolaris Not to insult you but I know what engines are in the 98
My question was directed to the OP as he didn't mention what engine was in his 98
And as we both know the 4.6 and 5.4 uses different ign. coils the 5.4 has COP's where is the 4.6 doesn't

 

[FordandPolaris]

Sorry glazed over the usernames while reading and thought the OP was asking that. Carry on.

 

[Bedrck47]

Lol

 

[randyj68]

Its the 4.6....

 

[FordandPolaris]

Can you see coolant or anything in the valley? I have heard that the intakes on the early 4.6's were made of plastic and tended to crack. Also check coolant hoses in that area for leaks.

Double check that the wires are going to the correct cylinders as well

 

[stamp11127]

Randy please add your Expy info(year - engine - trim) to your signature so that future questions / replies are tailored to the correct year.
This can be done under the user control panel towards the top left of the screen. If you need any help please ask.

 

[Bedrck47]

agree with FordandPolaris
check that the correct wires are going to the correct coils
the coil packs on the 4.6 fire two cyls at the same time and if the wires are crossed it will cause a misfire.

 

[Bedrck47]

randy read this

Part 1 -How to Test the 2 Coil Packs (Ford 4.6L, 5.4L)

 

[randyj68]

I dont see any coolant leaks. The wires look new..when I checked the connection with the wire at the coil it had dielectric grease. There's a minor exhaust leak but I was thinking that would throw a lean code. Just a little confused why it would clear up a little while then start back

 

[FordandPolaris]

Well all I can suggest is replacing at least the plug, then try trading the wires around to see if the problem moves to another cylinder (to clear the wire as the cause), and if those produce no results, the fuel injector would be next.

A crack in the porcelain of a plug can allow it to jump to the block and cause a misfire, really hard to know until you pull out that plug.

 

[randyj68]

The prior owner apparently tuned up the truck, they broke the spark plug for cylinder 4....alls good so far, hopefully nothing major will pop up. Thanks for the responses

 

[spud]

Ya Jinxed my ride, lol #3 out of the blue starts misfiring on me tossing up a P030 code on the reader. Plugs and wires are less than 4K on them (does not mean one could have gone bad) This miss went away for a bit then came back on after a small road trip was doing good, pulled into a parking lot and it started jumping and sputtering again and then service engine light came on blinking. So fun time to see what is its issue.

 

[FordandPolaris]

Ya Jinxed my ride, lol #3 out of the blue starts misfiring on me tossing up a P030 code on the reader. Plugs and wires are less than 4K on them (does not mean one could have gone bad) This miss went away for a bit then came back on after a small road trip was doing good, pulled into a parking lot and it started jumping and sputtering again and then service engine light came on blinking. So fun time to see what is its issue.

Start with the spark plug! Haha. Good luck with the fix, 3 isn't too bad to get to.