weadjust

I have a 06 4.6 I purchased new with 6 miles. I bought new spark plugs at 100,000 miles with plans to change them when the MPGs dropped off. That never really happened. At 160,000 miles I was averaging 18 MPGs for the last 10,000 miles on my Ultra Gauge. Finally changed them about a week ago.

Pics of the plugs below. #2 & #3 (on left) didn't need a ratchet to remove them. They were barely hanging on by a thread or 2 before they probably would have eventually been blown out. Note the carbon/exhaust build up on the plugs and high temps on the boots. Gaps were not in spec but I have never had a misfire and all COPs were the original motorcraft installed at the factory.

blupupher

iTrader: (2)

2 & 3 were definitely getting some major blowby there. You should see a little increase in mileage there for sure, probably run a little smoother also.

Heavy_Metal

So you just did it old school (used a ratchet and spark plug socket)?

Ive developed a slight miss at 1000-1400 rpm in OD so im replacing the cop boots and springs to see if thatll help.

Ive only got 73k on a 07 5.4 so I figure 9 year old boots should go.

Nice job not breaking any of those buggers.

robertsunrus

Hi, my 2000 Navigator with 32 valve 5.4 L V-8 has 127,000 miles on the original plugs and still running great. When the time comes, I will have someone else change them.

2008__XL

OP has the 4.6. They don't break.

weadjust

I was surprised I couldn't hear the blowby. I did replace the boots and springs on 1,2,3,5,6,&7. New COPs on 4 & 8 due to being in the back and difficult to reach. I kept those two old COPs as spares.

Heavy_Metal

Ahh. Thank ya.

bourgeois1269

Wow !! How does it run now ?

650NutKase

I would give them and extra 1/8th turn to make sure they dont blow out in the future.

weadjust

Runs like new. Prior to changing the plugs I started getting detonation/clattering sound when going up hills. Most likely cause by the blow by in #2 & 3 due to the lower cylinder compression.