This sucks.

My truck idles like an old 7.3. i did the plugs about 5k miles ago. I keep up with maintenance fairly well. pickup has a little bit over 130k miles on it. Within the last week the miss has started getting noticeable. I crawled under the hood and checked the cops to make sure there wasnt any damage i could see. How do i go about checking the cops and/or fixing it? I havent had any codes thrown.

btw, i have a 4.6 and used motorcraft plugs.

heres a pic for ****s and giggles.

thanks guys.

 

Are you sure you torqued all the plugs?

 

Yes they are all tight, but you have scared me. Im gonna make sure they are torqued tomorrow.

 

Did you use Motorcraft plugs? Did you grease the cop boots before putting them back on?

 

did you attach the thing-a-ma-jig to the whatchamacallit?

Just playin', hope you get it resolved.

 

I have a feeling your COP's are starting to burn up. My wife's Mustang kept burning up COP's after it hit 100k. It seemed I was replacing one every month. It would run like crap and never throw a code for the check engine light. However, we had a hand held tuner and it would show me the code for " misfire on cyl X". I would replace that cop, clear the code and it ran great until another Cylinder's COP bit the dust.


At idle we would also smell an unusual amount of unburnt fuel ( but we also had no cat's on her car).

 

I wouldnt mind just replacing the cops. it had a slight miss before the plugs, still has the same ones. seems like after i replaced the plugs it idled fine for a little bit. after a few weeks it started to get a rough idle again.

 

Sorry for the longer than necessary post on this subject. - COP Coil Over Plug Diagnosis and Replacement
I have had a 1999 Ford F150 Supercab Lariat since 2004. Bought it used in 2004 with about 100,000 miles on it. I love this truck - drives like a dream - until one or two of the Coil-Over-Plugs (COPs) starts making
it run like dog crap. Had the truck for about a year until it started the bumping and hesitating up hills or under loads - then it was happening all the time. I have about 190,000 miles on my Ford F150 today.
This/these forums have been instrumental in my understanding of how this engine operates (5.4Liter Triton v8). I have lurked on these forums for years to get info on how to fix my dang truck - and for the most part - am thankful for the many posts on how to diagnose things and stay away from the crooks at the dealerships.
The first time this happened did not have check engine light code (CEL) to diagnose the problem. Bought a couple of COPs and tried to remove and replace until the problem went away. No luck. Then I decided to pay for brand new COPs and new plugs and do the job right. Bought COPs from ebay (dont remember the dealer) for about $200 back then and changed each one. This was still a bargain considering that the dealer wanted $800 for the diagnosis and replacement. Truck drove like a dream again - for almost 3 years. When the bumping and hesitation happened again - had some engine code this time. Bought one from the friendly autostore and replaced it. - sure enough still had the problem. Ended up buying a set from ebay for about $90 (used abcmarts on ebay). Hell of a lot cheaper than $65 each from the autostore. Replaced all eight again - along with the plugs - back about one year ago. (December-2009)

Two weeks ago ran into the same problem - bumping and hesitation. But I noticed that it happened only after Ive been driving it for about 20 minutes. No CEL this time. Since money is tight I didnt want to pay the $85 bucks or so to replace all the COPs since I just changed them one year ago.
I had read from these forums that the primary resistance on the COP (two terminals that the connector hooks to should be nominal 0.55 Ohms with a range of between 0.3 to 1 Ohm. ANd that the secondary resistance measured from one of the top terminals to the connection on the spark plug should be betwen a range of 5.5 kiloOhms to 11.5 kiloOhms.
So, I decided to check each one and find the bad one. Bought one new COP from the autostore - making a guess that only one went bad. We had a week of dreary and wet weather and water may have gotten down into the COP plug and killed it even though I put a good amount of grease on the rubber boot to try to insulate it (even have gone as far a putting Blue RTV around the boot to keep moisture out).
Bought a new Accel COP since it ran the cheapest at $35. The procedure was to replace one COP with the Accel and drive the truck until it warmed up or the bumping / hesitation presented itself. Then drive home and replace the Accel with the original COP and go on and check another cylinder. I decided to do this one Sunday wicked a** cold day.

New Accel Resistance = Primary -> 0.9 Ohms; Secondary -> 5.75 kiloOhms
First --> Truck Cold ; Replaced COP #8 Resistance (Primary -> 0.9 Ohms ; Secondary -> 6.43 kiloOhms)
Drove the truck for 20 minutes and the truck started its bumping again. so it was not cylinder #8. Drove home and swaped out another cylinder. Did this for all eight cylinders - taking a shorter and shorter driveafter each swap out (since the engine was already hot - the bumping and hesitation presented itself as soon as I drove down the block). The problem went away after I remove and replaced the LAST one.

Heres a list of the measurements:

Right Side of the Engine:
Cylinder #8 : Resistance (Primary -> 0.9 Ohms ; Secondary -> 6.43 kiloOhms)
Cylinder #7 : Resistance (Primary -> 1.0 Ohms ; Secondary -> 11.34 kiloOhms)
Cylinder #6 : Resistance (Primary -> 0.8 Ohms ; Secondary -> 11.22 kiloOhms)
Cylinder #5 : Resistance (Primary -> 1.0 Ohms ; Secondary -> 11.23 kiloOhms)
Left Side of the Engine:
Cylinder #1 : Resistance (Primary -> 1.0 Ohms ; Secondary -> 11.18 kiloOhms)
Cylinder #2 : Resistance (Primary -> 0.8 Ohms ; Secondary -> 11.53 kiloOhms)
Cylinder #3 : Resistance (Primary -> 0.8 Ohms ; Secondary -> 11.42 kiloOhms)
Cylinder #4 : Resistance (Primary -> 0.8 Ohms ; Secondary -> 11.83 kiloOhms)

I replace cylinder #4 (the one in the very rear of the LHS of the Engine) with the Accel COP and it was the difference between night and day - instantly noticed an improvement just driving down the street. Notice that the warm COP measurement test had a secondary resistance of 11.83kOhms - which is outside of the 'acceptable' band.
The next day I measured the COP for #4 (the bad one) and re-measured: (Primary -> 0.8 Ohms ; Secondary -> 10.32 kiloOhms) It seems that the resistance changed between a hot and cold - that explains why the truck seemed to drive better until it had warmed up. Hmm. I hope the Accel COP lasts a while - based on what Ive read from these forums - I picked one of the worst.

Here are my lessons learned:
(1) Make sure the engine is heated up and driven before you start swapping COPs
(2) Change out the hardedest COPs first - the ones in the back (#4, #8) and then (#3, #7) since those are the ones that seem more prone to damage due to moisture.
(3) Don't rely on just the resistance measurements to determine if the COP is bad.
(4) Since you are changing out the COPs - go ahead and check or change out the spark plugs while you are at it.
(5) Don't play the COP swap-out-game unless you have a known good COP - You may waste a lot of time.
(6) Keep a set of a few (known good) COPs with you and tools you would need to replace a COP on the spot if the CEL code tells you which one might be bad --> good if you go on a long trip.
(7) Keep reading the forums.

Hope this helps somebody.

 

It does help. i am gonna find me a set of cops.

 

VERY TRUE!!!!

For my wife's 2001 GT.... we had a complete set from my Dad's 01 Mustang. He had swapped to MSD coils so I had is set of stock COP's. Any time we took a long trip I would throw the set in her trunk haha.

 

Thanks man, now that's a good first post, welcome to the site.

 

Thanks markops2002,
This is a HUGES help. Just started on the 99 Navigator - 144k miles on 5.4. Very Very helpful. Tommorrow my work begins.
Thanks,
Terry