'94 Ford 4.6 Spark Plugs

[Fifth87]

Just purchased a '94 Grand Marquis, story and pics to follow at a later date.
I am uncertain if the plugs have ever been changed, and with all I have heard/read about the 3 piece plug, threads pulling out or ejection, I am electing to pay to have this done. My question is this: Did Ford ever modify the plug design, so going forward I can change them myself without fear of breakage?

 

[melk]

it’s generally easier to change plugs on the 4.6 than the 5.4

 

[SwampSurvivor]

That's going to be a 2 valve 4.6, so it doesn't have the 3 piece plugs that break off in the head.

It has the threads that strip out. They do that because the factory torque spec is way too low, then they start to back out and just take the 3 threads when they eject. The solution is to slightly overtorque.

 

[wtd]

Just purchased a '94 Grand Marquis, story and pics to follow at a later date.
I am uncertain if the plugs have ever been changed, and with all I have heard/read about the 3 piece plug, threads pulling out or ejection, I am electing to pay to have this done. My question is this: Did Ford ever modify the plug design, so going forward I can change them myself without fear of breakage?

That car should have a conventional style plug and not the three-piece ones used in the 3 valve engines which were used in the mid 2000's.

 

[Cujet]

You should have no problem changing the plugs on that engine. Nothing special about it. The spark plugs are not the ultra-long versions found in the early 3 Valve versions of that engine. While this pic may not be the exact year you have, it is very close and it does show the conventional spark plug bores you have.

 

[D60]

~28 ft lbs. It's easy. Your horror stories are of the 3V

 

[thastinger]

~28 ft lbs. It's easy. Your horror stories are of the 3V

That torque spec has changed a lot over the years. I have a 98 5.4 2V and when I first started changing plugs the spec was 14ft-lbs with anti-seize, the Ford eventually changed it to 28-32ft-lbs without anti-seize. I've never chucked a plug from either 2V 5.4 we have(x2), even when I was using the 14ft-lb spec.

 

[ARCOgraphite]

Given mileage and year, this will likely be (at the very least) the third set of plugs going in.

I would not run a fine tip IR on a waste spark share coil pack ignition. This is a good application for Denso TT- at least on the "wrong fire" plug. IIRC these 4.6 came with two different plug P/N from factory for specific cylinders - possibly Pt tip/gnd

 

[SOUNDMAN5000]

I have owned lots of crown vic my fist being a 2002 was a LX the I have owned 7 retired Police vics.
I remember in the 2000's as I remember reading online Ford had a issue with I think truck 4.6 ( sorry can't remember ) but was a issue with the plugs blowing out of the engine. The plug was redesigned with more thread that in turn changed the heat range but Ford started selling that new longer thread plug and when I changed the plugs in my 02 that factory plugs did have less thread than what Ford sold me to replace then with. I always felt like didn't run a quick with the new plugs ( heat range had changed ),
Thats all I got but the OEM plug was changed sometime after my 02. I got it in 04 so may have been changed sometime in o4-06.

 

[slacktide_bitog]

As everyone else said, they didn't use the 2-piece spark plugs back then. That came int eh mid 2000s 3v 5.4, which the panthers never got.

Use Denso Iridium TT plugs and NGK wires

 

[OVERKILL]

Firstly, as others have noted, the 3-piece plugs are only found on the later 3-valve engines, which were not used in the Panther cars.

Secondly, from what I recall, the 3-thread issue, where the plugs risk blowing out, applies mostly to the PI-headed cars, which is 99+. This is an NPI head:

It appears to have considerably more threads than the pre-revision PI heads.

 

[D60]

My '07 F150 4.6 2V spit a plug randomly one day, so any model year can be affected

D

Thread 'Ford 2V spit a plug'

May 13, 2023

'07 4.6 in F150. About 235k miles

Yesterday it spit the #3 plug.

Can anyone identify this broken metal piece? It's .2485" with calipers, not mic. Edit: it's magnetic, thus ferrous

I still get 140# compression on this hole so valve stem seems unlikely?

The spark plug is in intact. The strap is closed up but other than that I can't make out an impact mark to the outside of the strap (if it appears so, it's just glare from camera/lighting)

• D60
• Replies: 16
• Forum: Mechanical/Maintenance Forum

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[Lubener]

Not a three piece plug but a three thread spark plug hole. The 2V has a history of spitting out spark plugs along with the threads. Do not use anti seize and torque to spec. I believe the specification has been changed, do your research.

 

[MVAR]

Firstly, as others have noted, the 3-piece plugs are only found on the later 3-valve engines, which were not used in the Panther cars.

Secondly, from what I recall, the 3-thread issue, where the plugs risk blowing out, applies mostly to the PI-headed cars, which is 99+. This is an NPI head:
View attachment 293645

It appears to have considerably more threads than the pre-revision PI heads.

This is true. My old 94 T-Bird & 98 F-150 (both 4.6) never had the spark plug issues. Those started with the PI heads

 

[OVERKILL]

This is true. My old 94 T-Bird & 98 F-150 (both 4.6) never had the spark plug issues. Those started with the PI heads

My Expedition (2002) had the PI heads with the three threads, launched #8 twice, 2nd time, there was no putting it back and it had the Lock-N-Stitch insert installed by the dealership and I never had another issue with it. It wasn't long before my dad retired his 2000 Expedition (maybe within the previous 12 months?) that it launched #7 or #8 plug on the way back from the cottage.

 

[MVAR]

My Expedition (2002) had the PI heads with the three threads, launched #8 twice, 2nd time, there was no putting it back and it had the Lock-N-Stitch insert installed by the dealership and I never had another issue with it. It wasn't long before my dad retired his 2000 Expedition (maybe within the previous 12 months?) that it launched #7 or #8 plug on the way back from the cottage.

The TFS cyl heads for the 4.6 2V became popular real quick with the added perks of thicker decks, additional threads for plugs & obviously more flow. Those PI heads became hated by many in the mustang & lightning community.

I was under the impression for several years that the only PI heads having this problem were boosted & high compression builds. Wasn’t until about 15yrs ago did I realize stock vehicles were suffering as well

 

[OVERKILL]

The TFS cyl heads for the 4.6 2V became popular real quick with the added perks of thicker decks, additional threads for plugs & obviously more flow. Those PI heads became hated by many in the mustang & lightning community.

I was under the impression for several years that the only PI heads having this problem were boosted & high compression builds. Wasn’t until about 15yrs ago did I realize stock vehicles were suffering as well

Yep, some engineer determined that the minimum number of threads required for the plugs was 3, so that's what they used. The problem was that as soon as you changed the plugs, any small amount of galling, which was pretty much guaranteed, particularly on vehicles like the Expedition with rear HVAC with the plumbing located right on top of cylinder #8, which dripped water down that would get into that hole, meant that there was a propensity for the plug to loosen off and eject.

They did revise the torque spec a few times, but the ultimately fix was of course more threads, which the later PI heads featured. The "advantage" of only threading the very bottom of the hole was the "self centering" nature for plug installation on the assembly line. Since the plug would drop down into the unthreaded section and was thus very easy to install. This was the goal, and why the minimum acceptable number of threads question was asked, otherwise, they would have just threaded the entire hole, as that part, during head production, didn't matter.