I spent all day sunday changing the driver's side spark plugs. Here are some pictures i took showing what i removed and where the spark plugs are. I also included some pics of the old spark plugs... been in the engine since 1997 and 181,000 mi! The new plugs are Bosch platinum 2's.

These engines are notorious for ejecting the plugs and you have to be careful when you put new ones in because the engine has aluminum heads and the threads strip easily. I put anti-seize on the threads for the new plugs and torqued them to 8 ft/lbs. you can do 7-10 ft/lbs I think. This isn't much so just hand tighten them then use the torque wrench. I also put di-electric compound on the other end of the plug to keep moisture out of the connection between the wire and the plug. The plug closest to the firewall was the hardest to reach and took the longest time.

I will post the pics of the passenger side soon after i find some time to do them.

I can already tell there is improved throttle response even with 4/8 new plugs.

Feel free to ask questions about the process. I found a lot of help on the internet on how to do this and would like to share what I learned.

 

I have some Bosch P+2 plugs in my 94 LTC 4.6L....they returned improved smoothness of performance and about 5% better fuel economy compared to a set of Autolite single platinum plugs.

Your ignition system is EDIS-8 that fires two plugs in series. Plugs 5-8 fire at normal polarity, but 1-4 are at reverse polarity, consequently the ground electrodes on plugs 1-4 will tend to erode away. Since the P+2 plugs do not have platinum-loaded ground electrodes it is very wise to remove #1 plug at around 20K and check the status of the erosion and, contingent upon that status, you may want to change out the plugs earlier than you would an OEM set.

FYI: OEM plugs for your ride would have special platinum-loaded ground electrode plugs in 1-4. It's the only scheme, apart from double-platinum plugs, that can guarantee a 100K mile recommended change of plugs.

My LTC at 30K miles on the plugs shows no detectable erosion of the ground electrodes, but your ride may be different, so caution is the byword.