RE: 2003 Ford Expedition 5.4L - Eddie Bauer
105,000 miles

Another coil pack going bad or bad gas?

Starting Monday afternoon, after I filled up at Costco, I thought I noticed a slight "knock" in my engine after driving about 10 miles, before shutdown for the day. Then, yesterday (Tuesday) drove the family to the local YMCA. The knocks and misfires really were very consistent and noticeable from the fist engine start to the last engine shutdown of the day.

We only drove about 8 miles round trip, but, on the way home from the Y, I decided to fill up (half a tank to full), with "quality" gas at a Shell to see what my happen. We drove three miles home. The knocks and misses continued, but still, no check engine light came on the dash. After getting the family home from the Y, an hour later, I drove the Expedition to a local gym to play basketball. Misfires and knocks continued until Tuesday night's shutdown after return from the gym (about 6 more miles round trip driving). Still, no check engine light came on.

Now, today, Wednesday, my wife drove to the store a few miles. She called and said there is no knocking nor misfiring at all! It has "magically" gone away. I have any appt later this afternoon at my shop, but I wonder if it is an intermittent coil pack, if they still can find it relatively easily with all packs temporarily behaving and no check engine light.

Ironically, we had very similar symptoms two weeks ago, except the knocking/misfiring did not just go away on its own. At that time, the check engine light came on solid, relatively quickly, within just a few miles of driving after the knocking/misfires commenced at that episode. I took it to my local shop at that time. They replaced coil pack on #8. All was well for about two weeks, until Monday.

I did have all the plugs and the PCV valve replaced in December at 100,000 miles as the maintenance guide calls out to do. The vehicle ran perfectly well from then through March, until the coil pack #8 episode two weeks ago. So, with this current episode, as with the coil pack #8 replacement two weeks ago, I see it has highly unlikely any plugs are to blame.

All remaining coil packs except for #8 are the original.

.... Thanks for any tips.

 

You should still scan it for codes. A pending code can be there and the CEL will still be off.

 

ok thanks, I hope there are at least some pending codes.

 

Was it rainy or damp on the days your truck was misfiring? My '01 had chronic misfires in bad weather. I replaced the COP boots and generously coated the insides with dielectric grease. Problem did not recur.

 

Yes! Tuesday was very sticky and rainy! The weather is 25 degrees cooler, sunny, and not a cloud in the sky today.

Are the COP boots the same thing as the coil packs themselves?

Thanks for the tip.

 

Your truck has coil over plug (COP) ignition. "Coil Pack" is a distributorless ignition term that has stuck around. It refers to a group of ignition coils physically connected together with one coil provided per cylinder- used to be "Ignition coils 1&2" and "Ignition coils 3&4". COP means you have one coil sitting on each individual spark plug. Almost universally nowadays, guys who say "coil pack" mean COP. The boot is the replaceable rubber insulator attached to the COP.

From your OP I infer that you have the original COP boots still connected to original COPs. Your misfires could be due to (likely) failing COP boots or a bad COP itself (possibly). The rainy day misfires that I experienced with the 4.6L in my truck did not always show a CEL or even a misfire code.

There is a TON of information regarding COP recommendations that can be accessed using the board search feature.

 

I have posted this several times in other threads and for those who are on this regularly, pls dismiss.

To answer Todd's question, you can see what the boot is and how it deteriorates.

These COP's either work or don't. These boots will help to create an intermittent effect when moisture is more prevalent as noted above.

Boots can be purchased pretty inexpensively, although, we seen COP's pretty cheap, lately as a set online.

 

I had issues similar to yours in my 98 Expy. Not knowing when the last spark plug change was, I opted to replace the COP and spark plugs. I started with the three hardest ones to get to and sure enough, after swapping them with new ones, the Expy ran perfect!

I noticed on one of the COP's (passengers side against firewall), The spark plug well had dirt, sand and wetness in it. Looks like rain runoff was dripping down the windshield, into the cowl and eventually onto the engine where is was some how seeping into the plug well. Anywho, if the COP boot is old, worn, what ever...the dampness will cause her to run rough.

Just my 2 pennies.

 

That's the cylinder that collects coolant in the spark plug well when the coolant hose over it leaks. Just had this issue on my 4.6L

 

When you buy a new COP also known as a "coil pack" does a new boot also come with the coil pack or does the boot have to be purchased in addition to the coil pack?

Is there a way for the shop to check condition of each boot of all 8 coil packs (I have a 5.4L), without having to pull out each coil pack?

.. Taking my Expedition in to the shop again today, because the engine knocking has resumed, but, this time the engine light has come on.

Get this, when I started this thread, I took the Expedition in to the shop in mid April, the next day after I started the thread. Recall that no engine light came on for then. The next day, the day I took to the shop in mid April, the knocking had stopped! The shop found no pending codes, and, even used a spray bottle to "mist" water on the coil packs while running the engine and could not get the slightest knock!

 

The boots and springs come with the new COP. The boot and spring are also available as a separate kit.

Only if they have x-ray vision.

 

Just got it back, today it was cylinder #3 coil pack (and boot) replaced.

Back in late March it was cylinder #8.

 

You can never tell when they will go bad. I just change them as necessary. Replaced 2 of 8 in 317k.

 

Yes, that's what I have decided to do, and probably why the Ford maintenance manual doesn't say to replace them all at once at 100,000 miles like the plugs.

I think time is an equally important factor. My Expedition "only" has 108,000 miles, but, that's over 11 years. I think time is a factor because moisture and corrosion can eventually wear electrical stuff.

How old is your Expedition with 317,000 miles?

 

As noted in my signature, it's a 1999. The boots crack over time and short out against the plug hole wall, giving you the impression that the COP is bad when most of the time, replacing the boot will resolve.

Good luck.