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Wednesday, February 25, 2009

Ford Coil-Boot Assembly




I had a great response in E-mails after my Ford Expedition post, so I thought I'd clarify a point I made about expensive tune-ups on Fords with individual coil-boot assemblies.


I mentioned how costly Ford tune-ups can be. The above pictures illustrate what Ford has replaced the spark plug wires and coil with in the last decade. The boot and coil assembly you see above is mounted on each cylinder spark plug. Although Ford doesn’t call for replacement of the spark plugs before 60,000 miles and later, when the spark plugs are replaced these boot and coil assemblies should be replaced with them. It’s expensive, but will save the added cost of a diagnostic check and computer scan later due to a misfire code causing the check engine light to come on. If a misfire takes place for an extended period the catalytic converter assembly will be damaged. On Ford, that cost makes the tune-up seem cheap in comparison.
The labor cost really adds to the expense of a tune-up on Ford’s vans. Removing and replacing the spark plugs and these coil and boot assemblies is quite time consuming – especially if doing the job in a van’s restricted engine compartment. These vehicles run extremely well, but like all the others rolling down the road, they have their quirks. 
That’s all for this update, but if you’re appreciative of the information, here is a link to my new novel COLD BLOODED for Nook and Kindle. If you’re kind enough to read it and like it, please review it on the site you purchase it from. Thank You! Every little bit helps my writing gig. :)



15 comments:

Anonymous said...

Hi Benard,
I have a 2005 Lincoln Navigator and recently I took it in to get serviced and I was told that 2 spark plugs and coils needed to be replaced and that was causing the misfire. I did not get it serviced that day but then had to take it in because it would not start. I was then told I needed a new starter. I ended up replacing the start, plugs, coils and fuel injectors.....two weeks later my check engine light goes on and now I need a catalytic converter. It's speacial order so I was told to go ahead and drive the car for the week or so while waiting for the part. But in doing so will I cause something else to go wrong with my car? Also was the starter related to any of this??

BernardL said...

Anon, I don't believe the starter had anything to do with the misfires, but the continued misfires are what killed the catalytic converter. Driving with the cat partially plugged can cause problems. I would drive it as little as possible until you get it replaced.

Anonymous said...

can you give me any ideas of what I might look forward to. I've already driver back and forth to
San Jose and all over San Francisco. Hopefully if I know what to expect I can blame it on them when it happens.

BernardL said...

Loss of power, Anon, meaning it would probably labor to get up to speed.

Ariel said...

Bernard, I'd welcome some advice. I'm looking to buy a used '05 Expedition with 95,000 miles. The current owner got it from a Ford dealer 11,000 miles ago. Shortly after he bought it, the catalytic converter needed replacement. Dealer split the repair bill with him at cost. Sounds like it might have had this misfire problem? Seems to run great now, and my mechanic gave it a thumbs-up. So should I figure that this problem has been resolved? What would you look for? What would you do as far as preventative maintenance if you bought it? Or would you stay away?

BernardL said...

You are right to worry, Ariel. The Expeditions have had numerous problems including electric fuel pump problems, electronic throttle body problems, throttle position sensor problems, trans problems, etc.

To address your specific question I would want to know if the spark plugs and boot assemblies have been changed. The spark plugs on that engine are known to break off and also to strip the threads out of the head during removal. If the ones on your Expedition have never been changed that will be an expense you will have to deal with very soon after your purchase. You may want to read over this post I did on a customer's 05 Expedition and the comments section - http://bernardsblog.blogspot.com/2009/02/throttle-position-sensor.html

Ariel said...

Thanks. That post today on the other thread was from me, too.

Contacted the dealer that sold to the current owner. They did nothing other than change fluids and replace the catalytic convertor. So if plugs were repaired it was in the "black hole" period before it got to the local Ford dealer. I guess if I bought it I'd change the plugs and coil assemblies just to be safe. But would I then be safe from this misfire problem and its consequences?

BernardL said...

There's really no way I can know that Ariel. Any used vehicle is a gamble. You could purchase a detailed service contract to cover all future repairs.

Ariel said...

Fair enough! But what causes the misfire problem in the first place? If bad plugs/coils then a new set should solve this problem. Yes? And what problems does the issue leave behind once resolved, other than damage to the catalytic convertor (which on this vehicle has already been replaced)? Basically, I'm asking if a new set of plugs/coils would make this problem history. Thanks again for your patience and advice.

BernardL said...

Misfires can be caused by a multitude of problems, mechanical, ignition and fuel related. I'm not trying to be evasive here, Ariel. I have NO way of knowing about your potential buy from here on the Internet.

Ariel said...

More info: Dealership did some more digging into service history. Turns out the vehicle had two injectors replaced under an extended warranty. I'm betting bad injectors, not plug misfires, took out the catalytic converter. Reasonable theory?

BernardL said...

Unknown, Ariel. If the injectors failed electrically they would not shoot fuel into the cylinders and unburned fuel is what kills a catalytic converter - such as when an ignition misfire allows unburned fuel into the exhaust. If the injectors flowed too much fuel they could be responsible, but again how can I know?

David said...

Bernard, I have an 05 Mustang GT that had a coil boot assembly go bad. The dealership replaced it and all is well. However, I have a service contract but they refuse to pay for the repair because "coil" is not a covered item. The item that is covered is "spark control detonation sensors and controller". Does the coil assembly do any of that?

BernardL said...

I'm sorry, David, but no.

David said...

Oh well, thanks anyway.