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11,061 Posts
Discussion Starter #1 (Edited)
I took the Tbird for a drive yesterday, and it was running like crap after it warmed up; after the drive back home, it was obvious it was either having coil pack problems, or it needed plugs and wires.

Looking the engine over after it cooled off a bit, I found rainwater and tree crap in the rear most plug wells; having water or coolant in the wells is known to degrade the plug-wires after a while, so I checked the logbook, and these plugs and wires were installed in 2009, right after I bought the car.

That was about 90k miles ago, all interstate. :)

So, knowing that pulling the plugs while the engine is warm is a risky proposition, due to there being three threads in the heads, and not wanting to see them come out on the plugs, I waited until today to deal with it.

I have a fresh set of APP103 plugs, one range colder, which works well in Lazarus, and I'm going to go out and replace all this crap.

Just for shits and giggles, I'm going to document everything, as the older info is becoming harder to find.

Process follows. :)

To get the plugs out you need a spark plug socket, an extension (I use a 12"), a u-joint for same, a 1/4" blade screwdriver, a ~10" piece of 3/8" vacuum hose, some brake parts cleaner, a blow off tool, a shop-vac, and a mirror on a handle tool.

WD40 will sub for the brake parts cleaner, and a can of compressed air like you'd use on a computer will sub for the compressor/blow off tool. Or just a rag and a long, thin screwdriver.​

You may wonder, WTF do you need all that crap for? :)

The spark plug wells get surrounded by all kinds of crap, so you want to vacuum/blow off the top of the engine before you even pop out the plug boots.

Remove the inlet tube; that takes a flat blade screwdriver.

After popping the wires out, you want to look down into the wells, to see what kind of crap in in the wells.
After 10 years, I expect there to be crap, and I've already seen it on #4.
#4 and #8 are the first places to look when one starts missing, as the manifold likes to leak coolant there.​

If there is liquid in the wells, it's likely the wires are dead, even if they're new.

I've killed them in a week with a bad manifold.
(Cleaning the sealing surface, and gluing the manifold down with ultra black RTV fixed the leak, but I'll probably break the manifold if I ever have to remove it.)​

So, if there's crap in the wells, hit it with cleaner, then blast the crap out of the wells with the blow off tool, while sucking it up with the shop-vac. You don't want brake parts cleaner or wd on your paint.

Make sure the wells are clean and dry BEFORE removing the plugs, because anything in there will drop into the cylinder.

Stuffing a valve with an acorn remnant is a possibility; I saw it done once on a mustang.​

If you don't have fancy tools like a compressor, or a can of compressed air, or a shop-vac, you can clean them out with a rag and a thin screwdriver; it's a pain in the ass, but you can do it.

Keep going until they're clean.

Make sure the engine has sat overnight before you loosen the plugs.
I've had these out, and I always use anti-seize on everything I remove.
But I still won't mess with the plugs hot.

If you take them out hot, you will probably see aluminum embedded in the threads. A Helicoil is in your future, at that point, and most shops won't install them without pulling heads.
At least we don't have 3V heads, lol.​

Taking the Plugs Out:
Using the 5/8" spark plug socket, with the u-joint just above it, and an extension, remove the plugs. Be gentle. :)
I usually tighten very slightly, then reverse and remove. Barely move it the first time.
You will see the swivel helps clear the fuel rail. Don't pull the fuel rail, as some people say.
The rear plugs are a *****, you might need another swivel. I did on one car.
If the plug drops out of the socket, a magnet on a stick or screwdriver will pull it out.

Putting the Plugs back in:
Stick the plug in the piece of vacuum hose, Apply anti-seize to the threads, and drop it down and thread it into the hole.
This make the process so much easier; the hose makes it easy to not cross thread, as you can't apply that much torque.
The tightening angle for both new and reused spark plugs is 1/16th of a turn, after the plug 'seats'.

I went thru last night and checked the gap on the plugs.

Factory gap is 0.054".
Blowers, high compression, Nitrous, all make a difference; some people go as far as 0.032.
The tighter the gap, the lower the energy of the spark, except in extreme cases, as listed above.

People will tell you plugs are pregapped. This is ****.
No one at the part store is selecting you plugs for your car; they're pulling from a bin of XXXX plugs.
If they get dropped, the gap can be zero, so check it.

I use a 0.060 Wire type gauge as a 'no go' gauge, and an 0.050 as a 'go' gauge; exactness is not that required.
A wire type gauge will not be dependent on you holding it a the correct angle to read correctly.

The ones you remove are going to be 0.070 (or larger), and it's rarely the plugs that fail. Usually it's the wires, because the high voltage will increase to match the gap, and at some voltage the wires will leak, carbonize, and fail.​

Safety message:

Our coilpacks can generate over 160kV in the right setup, so don't run your hand up the wires while it's running to find the bad spot.

You won't do that twice, anyway. :rofl:
I have a coilpack sealed in a block of insulation I use for projects, it can throw an arc about 3" in dry air.
They can kill you, no ****.

Plug types:

There are dozens of threads on what plugs are the best. OEM is best for me, but Autolite is usually cheaper than Motorcraft. And they made the OEM.

I don't like changing plugs every 15k miles, so Coppers are out for me.
But, if you're willing to regap and dress them every 10-15k miles, they are the best for high performance.

Our cars use a "Waste Spark System". What this means to us is that one side of the engine wears the tip of the plug, one wears the curved electrode.
This is why you want "Double Platinum" plugs; they have a little puck of platinum on both electrodes, and both sides will wear out at the same time.

All of the "Special" plugs will wear the tiny tip off down into the center electrode in about 15k miles.
I did this personally with a set of Bosch twin electrode plugs. 4 of them had cracked the center into pieces when I took them out.
The keyword for me is "Double Platinum". :)

Odd note: Ford being cheap, there were originally two part numbers for our plugs; one had the platinum puck at the tip, one on the curved electrode.

Technically, you could wear out a set of double platinums, regap them, and swap sides, and get another 100k out of them. :)
Only the side where the electrons land get blasted.

I stole this list from a post by Superduty, here:

AWSF-32C / stock heat range - copper plug
AWSF-22C / 1 Heat range colder - copper plug
AWSFA-12C / 2 Heat range cooler - copper plug
AGSF-32C/ Recommended for FRPP heads(not sure on heat range)

TR-55/ 3951/ Stock Heat Range
TR-6/ 4177/ 1 Step Colder
BP7EFS (PN - 3526) BR7EF (PN - 3346) two steps
R5724-8 (PN - 7317) two and a half steps
R5724-9 (PN - 7891) three steps
R5724-10 (PN - 7993) four steps

764s / Stock
103s / 1 heat range cooler < this is what I'm putting in. Autolite makes the Motorcraft brand.
AR94 / 2 heat range cooler
AR93 / 3 heat range cooler
AR92 / 4 heat range cooler

YS-59C / -3 or -4 below stock heat range

IT16 / stock heat
IT20 / -1 heat range
IT22 / -2 heat range
IT24 / -3 heat range

Small update

Motorcraft sparkplugs have changed part #'s and some are now only aval in a full thread design, new part #'s are as follows......

SP-447 replaces the AWSF-32-C & AGSF-32-C, Full Thread design-stock heat range in a copper core
SP-505 replaces the AWSF-22-C & AGSF-22-C, Full Thread design-1 step down from stock, also copper core
SP-494 replaces the AWSFA-12-C still a 1/2 thread design-2 steps down from stock, copper core

There are a ton of wires out there. IDK about those, I always buy the Stock Motorcraft wires; they're expensive, but last a lot longer than the one set of pretty aftermarket ones I bought.
They did look cool, but the 10mm wires don't fit the holders, and they died after a year.

This is the fun part. :)

But, I've done this enough to have it down. (famous last words, lol)

Here's the factory diagram:

You will notice as you pull them out of the box that there are varying lengths.
You can either remove one at a time, and match it up, or here's a list of the lengths that go to each cylinder:

CYL# ..............Number ranking of length, 1=shortest, 8= longest.

Cylinder #1 is front passenger, #5 is front driver's side.

Left coilpack is:

Right Coilpack is:

Use the Dielectric Grease LIBERALLY all over the boots, inside the boots, inside the coilpack ends.
I apply a 1/4 bead around the boot to try to seal the spark plug well; I've had mixed success with that.

Now I have shade over the car, so I'm going to go do it. :)

I hope this helps someone; I was looking at my notes, and they were everywhere, so I thought I'd put it all here.

Super Moderator
11,061 Posts
Discussion Starter #3
There's actually a Large swarm of bees across the street from my driveway, so the tools are out, but I'm inside, hanging out with the cats.


Iwas pulling all this together from different logbooks, and my scribbled notes, etc. so I decided to do a thread while I waited.

They're actually honeybees, so I decided fire was out; I haven't seen honeybees in years.

I guess I'm letting the plug wells dry out; we had a really hard storm last week, and the bird was parked at an angle; I think it washed everything off the hood/engine into the rear wells.

Super Moderator
11,061 Posts
Discussion Starter #4

2,135 Posts
Great write up!

One step I have always done is to either put a piece of duct tape along the fuel rail or wear gloves, otherwise you WILL scrape your hand at least once on the sharp edge on the fuel rail.

Also, when doing the plug wires, I always remove the alternator. It makes arranging the wires in the looms a breeze, and you can try to arrange them so there is minimal contact with the hot engine block.


Super Moderator
11,061 Posts
Discussion Starter #6
By the time I'm replacing wires, they are usually well worn, so I just grab them with pliers and pull them out. :)

That prevents leaving skin on the fuel rail or corners of the injector clips, lol.

It makes the wires not so reusable, but they're not usually any good by then anyway.

I stopped running the wires under the alternator years back; it makes them all fail there first, but it's hidden, and a pain to diagnose.
There's just too much heat there.

But it does look nicer. :)

I buy a few packs of these:

You can find them cheap, in multiple colors.

Hitting them in a cup of hot water before you install them makes it really easy.

I make sure that two of these are standing the wires off the top of the alternator by putting the open side up, giving it a gap for cooling.

I use the factory clips too, I just use the cheapies to make sure the wires don't touch hot stuff.

The wires I took off were leaking everywhere they were close to metal; they were put in in 2013, not 2009 as I said before, there was a post in the other thread I finally found. :)

I'd just plan on doing wires every 3-4 years, and by being proactive, you won't ever have problems. :D

Super Moderator
11,061 Posts
Discussion Starter #7
I finally finished the Spark Plug and Wire replacement.

I also cleaned the MAF, changed the air filter, cleaned out the TB blade of accumulated gunk, and reset the computer.

It runs great.

I'll post pix later, but this is the most Fucked set of spark plugs I've ever changed out of any vehicle. :surprise:

The wires were wasted, and arcing in multiple points.

I'm pretty sure, despite the Motorcraft label on them, that they are cheap fakes.

For one, the spring clip design on both ends is different than the other sets I have, and they are steel, not bronze or brass, or whatever the MC ones are.

This is what all the others, including the ones I put in today look like:

I'll post a pic of the bad ones here: (later)

The APP104 plugs I put in in 2013 are all over the place; I'm going to get out the stereo microscope and have a good look.

A few cylinders look like what I would expect after 90k miles; worn, but serviceable. One looks almost new.

A few cylinders are burnt to heck, missing the platinum puck, and associated damage.

All were oil covered up the threads, they were not tight at all. :facepalm:

I had a helper doing this with me; IIRC, I started them, he was to tighten them. LOL.
(Don't do Drugs, kids! It rots your brains.)
The last time he helped me, he wanted to do something to his truck, so I let him use my ramps, which he drove over; way over.
That was it for me; lesson learned, lol.

I used a set of coilpack style mark 8 plugwires, because they were getting old sitting on the shelf, and they looked great.
They are exactly the same wires, except with a line molded in, I guess to tell them apart on the assy line. :)

I have heard that because they fire sequentially, plug wire 5 and 6 need to be separated; anyone know for sure, and are there any others?

I'm going to take it for a nice datalog tomorrow, to see how it's running.

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2,135 Posts
I changed the original platinum plugs in my '97 at 65k, and I was surprised how worn they were. I was also surprised they used a different plug on the right and left banks! I saved them for reference. I also saved the original "numbered" wires. I only changed them because I had a set of new Motorcrafts from Ford that were sitting on the shelf for at least 8 years.

It made a nice difference in throttle response on the hit. Thought it would make a little difference in gas mileage. But nope, it went the other way!

Grog6, I would like to see a pic of how the wires fit not going under the alternator.


88 Posts
I found your article well written and very helpful.

I chased an intermittent unflagged misfire for weeks in my car, it would habe been simpler if I had used your method to eliminate possible variants.

I did end up rooting out a cracked coil pack, and a broken Accel plug wire boot in the process. That wasted spark and very high voltage coil packs only missed intermittently with full-blown faults that would present on any other ignition as continuous, flagged, and simple. I think I broke the wire myself probably.
That all finally made me understand the xmission solenoid issues exacerbating the problem with similar symptoms. Our TCC is really played out, we need to upgrade desperately to a better TC that is affordable.
I totally agree and promote the liberal use of dielectric grease on these cars everywhere you see an electrical connection.

These cars are built with a robust and high-quality wiring harness using state of the art connectors and superior craftsmanship. I inspected every inch of mine and at 25 years old, it is immaculate except where I bruised it. The use of quality dialectric grease will help preserve this component and the systems attached by maintaining a gastight connection, lubricated and water free.

1 Posts
Great info... same engine in my 98 Mustang GT manual. This is my first modular engine, and found it "rough" when idling. Turning the AC on (slightly higher idle) smooths it out considerably, but still a bit rough. A Ford mechanic suggested, strongly, sticking with the Ford spark plugs (for me SP432) platinum. I went from a Bosch double platinum to Ford and it was a slight improvement. After wires, coil packs, plugs, IAC, TPS and throttle body cleaner, seafoam and Lucas in gas for a few tanks, I'm realizing this engine is just not smooth at idle.... it is very smooth cruising and throttle tip in however.

1994 XR7 , 46 most every option. 66.000 miles. rustfree, from washington state.
298 Posts
thank you for the great wiring info. just got the motorcraft wires done right.
saved a lot of guessing.
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