I have a 99 F150 with 160,000 miles, and the 5.4. The #4 Coil keeps failing. I can get about 1000-2000 miles then it fails, I have replaced 4 in the past 2 months. I replaced it ones about a year ago.
I have checked for a leaking heater hose, no signs of leaks. not loosing any fluids. replaced the spark plug this time also, it was pretty dry and brown looking.
running fuel injection cleaner, and having the filter changed tomorrow.

Has anyone had the #4 keep failing? ANY THOUGHTS??
thanks

 

Just an idea but maybe the coil is good but there is a bad electrical connection somewhere.

 

I thought about a bad electrical connection and tried moving all the wires before I replaced the coil. a new coil seems to work every time, maybe there is a voltage issue, not sure? Is there any way I can check the harness without going to the dealer?

 

take one of the "bad" cops and put it on another cylinder. What controls the spark on these do they have an ignition module or is it in the pcm?

 

PCM, have switched the coils, once they go bad, they are bad.
I just had the fuel filter changed, the mech told me the filter was installed backwards? it has been in there since i have owned the vehicle, at least 80,000 miles, not sure if the filter can have any effect on this issue.

 

I dont think the backwars fuel filter would do this........search google and start a new thread "why is my cop repeatedly going bad". anything weird around the cop, any leaks? any tsb's. do you have diagram of the wiring. could there be a Diode or something tha tis not working...

*chase Rockledge or pawpaw down.....sometimes they know about these issues.....

 

I found this post in blue from another website. You would have thought that you would have thrown a code if it was lean and why is the same cop blowing out........never the less I though it interesting


Quote:
<table border="0" cellpadding="5" cellspacing="0" width="100%"> <tbody><tr> <td class="alt2" style="border: 1px inset;"> I was told by a part guy that a coil pack will work or it won't and you will be able to tell. There is no in between. </td> </tr> </tbody></table>
Totally incorrect. You have what's called a low grade misfire. This is caused by any one of the following, note #4 particularly:

1. Bad plugs.
2. Failure to use dielectric grease in the boots when replacing plugs.
3. Spark plug wires that need replacement (N/A with COP system).
4. Coil pack or COP that is breaking down under the load of trying to fire a very lean mixture, which is what you have at low RPM's in OD.

A coil pack or COP cannot be tested with just an ohm/volt meter. The dealer has the tools to test them under these conditions, but for what they would charge you to do it, you can simply buy replacements.

I had an intermittent miss on mine and even the dealer could not find a problem. Replacing the coil pack on speculation FIXED it. __________________
2003 F150XL 4.2 short cab/bed 4x2 5 speed manual 3.55 LS <!-- google_ad_section_end --><!-- / message --> <!-- sig --> <!-- google_ad_section_start(weight=ignore) -->

 

maybe you have a failing fuel injector and if therory #4 is correct maybe it is causing the cop's to blow..........just thinking out load

 

Did you put Dielectric grease on the plug end and the electric connection end.?.......is the #4 cylinder near something super hot?

 

I don't have one of these trucks. This is just some info that might help.

Some garages have ignition probes for COP ignitions. This lets them check the firing voltage and other characteristics of the ignition waveform. If they probed it shortly after a COP change, it could show if the waveform indicated some kind of stress.

I have read that having grounded metal parts too close to the COP can cause stress -- particularly if they have sharp edges or points. I think that they have to be quite close, but it is an issue.

Good Luck,

 

I have always used dielectric grease, based on the plug, I am thinking that maybe the injector is clogged and causing the cylinder to be extra hot or something, which is causing the plug failure. I do have a leaking exhaust stud , but I cant believe that is causing just the #4 and not the #3 or anything to go bad.
Plan is to replace injector, that would cover new plug, new COP and new injector and have the exhaust stud fixed. thats the only thing I can think. I have read every forum, the only other thing I see is that water may be getting in through the hood vent, and filling the plug,, I will check that by running the garden hose on the hood and see if there is any water.. It is just a weird situation that this coil keeps failing.
Thanks for all the posts and help

 

Wouldn't the plug fire regardless of whether or not there is fuel in the system or not.

 

yes but if you read the whole theory that i pulled off the internet . the theory says that a lean fuel mixture over time can burn out the cop!!!

 

Yes, I did read the whole theory but I just cant see how that is possible.

 

A good ohm meter can check resistance specs for these. I am not sure what it is off hand but the defective one will have a significant reading difference than the other good ones. Rain water and snow runs down fire wall and over time, usually in winter, the COP will fail as temperatures flucuate. Ford F150s are bad for this happening and one of mine went again. I am currently driving my BMW 7 Series sedan until I address it. Someone on here may have the correct ohm spec readings for the COPs. They can fail partially as well. Ford should have address this problem and the chronic front end component failures (ball-joints/tie-rods). I would give anything to have my old 390 CID powered 1976 F100 back again. If I was buying again, I would opt for an older truck with again with Twin -I Beam suspension.