OBD II code - misfire on cylinder 8
 

My wife's 2004 Expedition (4.6 liter V8) developed a rough idle and surge/hesitation/stuttering a week ago and I put the code reader on it. It says misfire in cylinder 8. I figured it was a bad plug wire (it really is time to change them), but discovered there are no plug wires on this engine. I found each spark plug has a coil directly connected to it. I figure the coil is bad and I should get a new one, but the problem is there seems to be very little clearance to remove the coil due to the fuel rail being directly above it. Can anyone share the best way to approach this or point me in the right direction for instruction on the procedure. I know - I should go to the parts store and buy the chilton or whoever's repair and maintenance book for her year model, but I really don't want to have to spend the dough for that, although the one I bought for my 98 F150 has been invaluable.

Thanks,
Stacy

Loosen the fuel rail and move it out of the way. You don't have to completely remove it but you can and if you do you may as well go ahead and get new o-rings for the injectors. Whatever you do just be sure the injectors are firmly in place when you bolt it back on! Also since you're under the hood anyway you may want to consider going ahead and changing all the plugs and coils. You can get a set of 8 COP's on ebay for around $100. Alot of us have used them and have had no problems. You'll want to use Motorcraft double platinum plugs. Oh, and use anti-seize on the plug threads....it'll make your next plug change a snap!

Do a search on this forum and you'll find several links to instructions on how to change the plugs, boots, coils, etc. Loosening or removing the fuel rails is not necessary but you will need several extensions and swivels.

How many miles on your expy. I started to have the misfire condition start on mine at about 70,000 miles. The COPS were not bad but all the boots needed to be replaced as well as the sparkplugs (so much for that 100k tuneup interval).

Be careful with the brand of plugs you use (search the forum, the recommendation is Motorcraft). Many people have reported taking the parts to their local garage and having them installed for reasonable prices. As I recall, the boots cost about $6/each at the parts store. You can get COPS and boots as a set on ebay for about $100 as the other poster mentioned (a COP at the parts store is about $40, at the dealer about $80).

A plug and boot change at the dealer is probably going to cost you about $600.

Good luck and let us know how things turn out.

I appreciate the info guys. Will start the search now for lunch. :)

With alittle fenesse you should be able to work the coil & boot out without loosening the fuel rail, Iv'e heard it being done the boot is flexible enough for it.:-X0A6

The problem isn't getting the boot out, it's getting to the screw to release it. I didn't take my fuel rail off but I did loosen it and move the back end a little just to ease the process. I imagine with a little effort I could have squeezed my girl hands back there but I didn't want to bruise my knuckles any more than necessary.

Well. I did my research. I think I will just replace the boots and springs and wait on the cop's until I have to. Seems like the stats show it is more likely that the boot has cracked on cylinder 8. I'll let ya'll know what happens.

Thanks again,
Stacy

Don't forget too, that water will get down into the spark plug holes around the boot - especially in numbers 4 and 8. At 100K mi. I replaced my plugs but started getting misfires on 8 so I went back in and found sitting water. Maybe I did not seat the boot correctly. I cleaned it all up, put lots of dialectric grease around the boot and have not had a problem since (2 years). Oh ya - 137k miles now on the original COPS, boots, and springs. Good luck, whatever you find.

I had to report back that I followed the procedures outlined in the instructions I found in the articles. Thanks for the heads up on that. I performed this little operation a couple of weeks ago and it took me 5 hours. I got to the parts store and they didn't have motorcraft plugs in stock. They only had ACDelco, so I went with those because I didn't want to drive all over town looking for the expensive ones. I used the shopping list outlined in the proceudres and I spent a total of about $110 on everything... and boy was it worth it. The whole procedure was really pretty easy. I just took my time and developed sort of a routine. The back plug wells were wet and I found a lot of rust on the number 8 plug (which was where the OBDII code said the problem was). When I got it put back together, she ran like new. Thanks for all the help here guys. I guess I'm gonna have to get a premium membership here if I keep leaning on ya'll for help. I'm really beginning to find that working on these new vehicles is not the pain it seems to be. With the advent of computers and electronic ignition I just figured a person really can't work on their own cars anymore. I was wrong on that. Thanks again.

Yep, can do! It just takes more than a cheap socket and screwdriver set to do it now. :)

I have a 2001 Ford F150 that has been bucking and missing for about 4 months but never had service engine soon light come on until today. Got it read and it says #3 misfire which I know that is another coil pack. But I would like to change it myself? Is it hard?? Do I have to remove anything? Looks like it might be kinda tight?? I don't know where to find directions on the web! Please help!!!:-wink

You can do it.

I just solved P0303 yesterday that suddenly popped-out, by replacing #3 coil (aka COP - coil on plug) - it's not as hard as #4, or #8 which are directly below the firewall area, but nevertheless is in tight location. For my 5.4 V8, cylinder numbering is as follows:

firewall-area
4 8
3 7
2 6
1 5
front-area

Not sure about 4.6, so double check if your is.

Compressor will be handy, so you can air blow any dust/debris near the COP before removing it so no craps will go into your plug hole (which can potentially end up in your cylinder). The bolt that secure the coil is 7mm - if you're only planning on doing #3, 1/4 socket and some extenders will do the trick. (To do #4 and #8, I ended up getting (not universal) swivel #7, (http://www.sears.com/shc/s/p_10153_12605_00943193000P) and a box 7mm.

I was able to remove the #3 coil without removing the rail, and if you wish to replace that plug, I'm sure you can too without removing said rail. I didn't when I tuned my XP back in '05 and was able to remove all coils and plugs wiht rails on both sides installed.

For plugs, get either MC double plats or Autolite double plats for longevity - you only want to do this once, believe me, lol.

I happen to have a spare coil and a reader, so yesterday's repair was like free and only took an hour tops, only because it was too darn hot yesterday.

Now, I'm trying to research here if the ebay cheap coils are any good - AZ has it for almot $50 each, whereas ebay cost like $10+sh. I'm guessing the dealer price for oem should be upward of $50. I'm comfortable in having a spare COP in the trunk, because we mostly use this beast now for long distance travel

Good luck.

Thank you very much it all helps a lot! I noticed #2 where you screw it down is broke from someone screwing it to tight. Is that a problem? I'm replacing #3 today but I was just curious about that crack next to the screw hole??

Also if you have anymore advice on changing #3 please tell me. My brother will be helping me and we have never done it!

Why does the water get around the plug on cylinder 8, is it a head gasket issue or something, i have to take out the coil pak and blow the water out every so often, and there doesnt' seem to be any rhyme or reason. The plastic engine cover was missing when i bought the vehicle (2002 moutaineer with 4.6L V8)

It drips from the heater hose joint that's right above that COP.