Almost 30k on Original Spark Plugs, Change or Not? - Mustang Evolution

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Old 05-24-2015, 08:40 AM   #1
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Almost 30k on Original Spark Plugs, Change or Not?

I have almost 30,000 miles on my 2003 GT (10,000 of those miles I placed on car since I became second owner last year). I have been replacing all fluids/filters, ten year old tires, etc, and got some new OEM spark plugs to install.

On all of my previous cars I would change plugs this old in a heartbeat, as I have read that miles and time can wear them out. On the Mustang I would like some thoughts as to whether I should, given the thread stripping issues.

The car accelerates smoothly for the most part, although sometimes it does seem to hesitate. Mileage and idling are both fine. I will likely be purchasing a tuner later this summer for it.

So, based on that info would you guys suggest I change plugs? Or keep the originals in?

Thanks!
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Old 05-24-2015, 09:00 AM   #2
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You might as well replace them. I waited a while to replace mine because of the same fear of stripping them. As long as you use a torque wrench and the proper torque there shouldn't be any issues. Mine was running just fine with my old plugs, but I had no idea how many miles were actually on them until I pulled them out. And I'm glad I did. Click image for larger version

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There is a write up posted on the forum somewhere. Make sure you follow it! There is also a debate on whether to use anti seize. I used a very small amount on each plug.


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Old 05-24-2015, 09:50 AM   #3
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Almost 30k on Original Spark Plugs, Change or Not?

When you do the spark plug removal make sure your engine is cold. You have a much lower risk of stripping out the threads. It's a method we use at my shop. We've done too many with the engine at operating temp, and striped the threads. When putting them in make sure they are properly gapped. And use a torque wrench to tighten them up.


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Old 05-24-2015, 11:29 AM   #4
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30k miles?
You still have 70k miles before the spark plugs need to be replaced!

The recommended interval is 100k miles.
I wouldn't mess with them until then!
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Old 05-24-2015, 12:47 PM   #5
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My thought is the longer they stay in the harder they are to take out .I did mine at 40000 miles. Change my sons plugs at 135000 mile original plugs didn't go to well stripped the threads on the head rather be safe then sorry.
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Old 05-24-2015, 02:59 PM   #6
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Replace them just due to age so they don't seize up on you. I'm sure the efficiency of them is just fine but why risk it.


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Old 05-24-2015, 03:13 PM   #7
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Replace them.
_______________________________________-----------------------------------_________
Spark Plug Design Flaws
Trying to remove spark plugs from Ford’s 3-valve 4.6L, 5.4L and 6.8L 2004–2008 engines can cause part of the plug to break off and get stuck in the cylinder head. The spark plugs were designed to need their first service at 100,000 miles which sounds great on paper, until you realize that:

It’s far outside of the vehicle’s basic warranty
The long service interval is actually one of the reasons the plugs break apart
Spark plugs from Ford Triton Engines
The pooly designed plugs
Ford came up with a unique plug design that has a 2-piece shell. At the end of the plug an electrode extends a bit beyond the threads and creates a gap between the plug and the cylinder head which gets filled with carbon deposits. The problem isn’t bad if treated at 30,000 miles, but over 100,000 miles – Ford’s recommended interval – it cakes the electrode in a concrete-like grip. Because the elctrode is welded to the bottom part of the shell, it creates a natural breaking point.

Ford ackowledges some of these issues in TSB 08–7–6[1].
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Old 05-25-2015, 11:34 AM   #8
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Quote:
Originally Posted by jek57 View Post
My thought is the longer they stay in the harder they are to take out .I did mine at 40000 miles. Change my sons plugs at 135000 mile original plugs didn't go to well stripped the threads on the head rather be safe then sorry.
Pulling them out or putting them in? I've pulled plugs out of high mileage motors and original plugs out of 10+year old motors (like the one on my engine stand right now) and they come right out. If you put them back in without a torque wrench tho... even going 1/8 turn past finger tight you'll likely blow a thread.

12-15ft lbs is spec and that is just a touch past finger tight. TBTH if you blow up the threads removing a plug its almost 100% because the previous owner did the plugs and did not use a torque wrench.

Quote:
Originally Posted by robb15033 View Post
Replace them.
_______________________________________-----------------------------------_________
Spark Plug Design Flaws
Trying to remove spark plugs from Ford’s 3-valve 4.6L, 5.4L and 6.8L 2004–2008 engines can cause part of the plug to break off and get stuck in the cylinder head. The spark plugs were designed to need their first service at 100,000 miles which sounds great on paper, until you realize that:

It’s far outside of the vehicle’s basic warranty
The long service interval is actually one of the reasons the plugs break apart
Spark plugs from Ford Triton Engines
The pooly designed plugs
Ford came up with a unique plug design that has a 2-piece shell. At the end of the plug an electrode extends a bit beyond the threads and creates a gap between the plug and the cylinder head which gets filled with carbon deposits. The problem isn’t bad if treated at 30,000 miles, but over 100,000 miles – Ford’s recommended interval – it cakes the electrode in a concrete-like grip. Because the elctrode is welded to the bottom part of the shell, it creates a natural breaking point.

Ford ackowledges some of these issues in TSB 08–7–6[1].
^This has nothing to do with the 2V or 4V. It is a 2005+ thing only for the Mustang.
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Old 05-25-2015, 12:16 PM   #9
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I usually do 50K but you can't go wrong replacing them at 30K. The older they get the more the gap widens and the coil has to work harder to make the spark jump. So replacing plugs makes it easier on the other electrical systems.
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