My 183,900 mile spark plug change...
Hey guys, I saw this thread and thought I'd add my experience yesterday when changing my spark plugs for the first time since I've owned it (just under 10,000 miles since I bought it 8 months ago). I'm running a 2004 SR5 with the 2UZ-FE.
About half of my coil pack bolts were heavily corroded just like some of the other posters in this thread, so I wondered if the plugs had ever been replaced. Well, the Denso Iridium Long Life plugs that I pulled out all had the letter "P" on the tip--from what I've read on this forum that is an indication that these were the original plugs from the factory! That's nearly 184,000 miles! I'm definitely impressed by the quality and durability of Denso spark plugs. The plugs really didn't look too bad, but had a bit of oil on a few.
I was expecting the coil pack bolts to break off, but had doused them in penetrating lube earlier in the day so they came out just fine. A few of the plugs weren't very tight either, definitely not what I was expecting--I expected they would be pretty hard to get out and worried about breaking them too, but they worked out alright.
I replaced all the coil pack bolts, and the new plugs are Denso Iridium TT 4702. Torqued plugs and coil pack bolts to 13 ft/lbs, no anti-seize.
I can say with certainty that it starts faster, idles smoother, has better throttle response and acceleration and will probably result in better mileage too but I've only driven it about 10 miles since I changed them last night so I'll post back on any mileage increase. I tend to drive pretty conservatively to get better gas mileage, so I was already managing around 18-19mpg (on paper) ((yes, you would be pissed if you got behind me at a stop light)), but I'm hoping there will be an appreciable increase in my mileage...maybe I can drive like I'm 28, rather than 68.
Overall, I took my sweet time on this job, probably around 6 hours total. I'd never done a spark plug change on a newer vehicle so I wanted to be extra careful...especially considering the appearance of my coil pack bolts--did NOT want anything snapping off because my T4R is my daily driver. I cleaned the coil packs up with MAF sensor cleaner, then put a light coat of lithium grease around the inside lip of the connectors to help seal out moisture and make them easier to pull off next time. Also made sure to put each coil pack back into the same cylinder it came out of...didn't know if that was necessary but I didn't want to take any chances, just in case. I considered ohm testing each coil pack but couldn't find what range they should be operating in so I will put that on hold--but haven't had any codes or misfires so I assume my coil packs are just fine for now.
Sorry for the long post, I'll get my pictures up now!