Thought this might be of interest to some of you techie types.
http://www.svtlightnings.com/sparkplugmisfires.htm
http://www.nbt-brunei.com/part/parts/denso_plug/

Note that the NGK TR-6 is what the SC'd Cobra community widely uses in the 2003 and up 4.6 DOHC power adder engine beasts. Better resistance to spark blowout at elevated boost, and very few misfires. Look how closely it tracks to the Denso's, and they cost a fraction of them. If your plugs are easy to get at, changing them out every 10-20k miles is cheap and easy.

I use Iridiums (Iridia?) in my S2000, one range colder than stock, as I seldom drive in stop and go. No fouling at all, and with the cooling mods, I feel that the heat-related spark retarding is minimized or eliminated.

RR.

 

I consider myself rather well versed in the ways of automotive technology, but I am too drunk and lazy tonight to read through other links, so I may as well be the first to ask Road Rage for a concise answer to the question: What spark plugs should we be using in our TLs?

 

Why not use the ones recommended in the owners manual? I'm certain that Mr Honda put some thought into spark plugs at the time the engine was developed. Moreover, both the NGK and Denso did quite well in the tests that Road Rage referenced.

 

The Denso Iridium plugs are probably the best you can get...The part number is IK16 for our stock engines...the IK20 plugs will also work. The 16 or 20 number is the amount of cooling the plug provides. The higher numbers (24 - 32) are for very high performance engines with turbos or superchargers that have very high heat durring combustion.

 

when does the manitenance minder say to change the plugs? i am at 14K and probably due for servicing soon. if i have to change plugs i would definitely want to get these.

 

You dont have too for a long time...manual says 100K if I remember correctly. I find that hard to believe, Im sure they will work that long, but you may lose some performance. I would just go ahead and switch them out now so you can enjoy them longer. You can get them off of Ebay for cheeper also.

 

Actually the manual does not give a specific mileage for spark plug change. It is #4 in the maintenance minder. Also in #4 is timing belt replacement, which is recommended at 100K under normal conditions and 60K under extreme conditions, so I guess you could extend the same mileage interval to the plugs.

My 96TL recommended changing plugs at 60K, and then later models came out using the same plug and recommended 100K, so I waited. Then, Honda got caught cheating on the check engine light in California so extended the emissions warranty and replaced plugs free under warranty. When I got it done I looked at the old plugs and they were still like new, so I would think you could wait for a substantial number of miles before changing the plugs.

 

What plugs do our cars have stock? 2004 TL

 

I use the Denso Iridiums in the S2000, but those plugs are easy to get at, and therefore to check. A car that spends a lot of time in the RPM range of a sewing machine needs really good spark.

Early D-I's had a problem in that the welds holding the iridium to the base metal on the center electrode occasionally failed - early adopters found out the hard way - when the plug head started to do a lap dance with the piston and cylinder wall.

Denso quickly fixed that, and i have not seen any problems since.

The stock plugs appear to have many of the design features of the D-I, but without the exotic metal. I doubt there is any practical benefit to using them in the TL, except to change heat index if you do a lot of hi-RPM track use.

I have seen cars @ 60K with platinum plugs, and they looked damn good (as on my 1997 Outback beater). I changed them out anyway, as I was doing a major tune-up, and had removed the battery and other parts needed to make access, so it made sense (like replacing the water pump whenever you do a timing belt change).

The only caveat I have with long dhange intervals is making sure that:
1) The plugs are treated to ensurte they do not galvanically "freeze" to the aluminum heads (dissimilar metals exhange atoms)
2) ensuring that the plug wire boots have enough dielectric grease to ensure they do not stick to the plug, making removal and replacement a nightmare.

If the plugs are reasonably accessible, I suggest removal, treat with a good anti-seize (I use marine grade), and then torque them back to stock specs to ensure they do not work themselves loose.

 

Ford recommends the same 100K intervals. I did not believe this either but did wait until 75K to change them out in my 4.6L SOHC. The old plugs were ok but somewhat worn. Plug gap was definitely much wider than spec. If you run your car hard or just want to make sure you have the best spark, mileage, etc. change them out at 60K. It's pretty cheap and you can do it yourself.

 

According to page 257 of the Owner's Manual, the stock plugs are:
NGK: 12FR6K-11
DENSO: SKJ20DR-M11