Your mechanic is wrong. Take the cover off and you can check a plug very easily. The best way is to get the proper size spark plug socket and a locking extension makes life very easy. I would check if you don't know.

 

OEM is always a good default unless there is some compelling reason not to. How did they look at 110K?

 

I would give myself the peace of mind of checking as the post below suggested. Do you have any service history? I only ask because you're at a mileage where you would also want to ensure the timing belt was done. Not trying to alarm you, just trying to be helpful.

 

Changed out my spark plugs this weekend. Car is at 120k miles. I pulled out Denso plugs that were very clean but the Iridium tip was worn down widening the gap. Lately My Idle was at 500-600 RPM's for some time now and every once in awhile the car would studder.

I installed OEM NGK Iridium Plugs and the Idle returned to 900 RPM's and the torque is back to when I first had the car along with the throttle response and smoothness of the engine.

I did use anti-seize Lube on the threads and electro-grease on the boots.

Note: I did not clean the throttle body yet, I wanted to see the difference on the new plugs alone. Maf sensor was cleaned during oil change a month ago.

Sorry for the crappy phone pic. Over time, you just don't realize how tired these old plugs are and how it effects performance

 

Why use anti-seize when Lexus and Denso / NGK say don't use it? Probably not a big deal but it causes incorrect torquing of the spark plug.

 

Purchased my car at 99,000 miles and now have 115,000 miles. Car idles quietly and accelerates fine. I assume they are the original plugs and I'm not planning on changing them for another 10,000 miles unless the car becomes symptomatic.

 

I did mine at 110k. They were due. Nothing was misfiring but 120k is a little much imo.

 

Well today most apply their own anti-seize compound to the threads at the factory. I use a very small amount meant for aluminum heads, it's habitual and I've never had issues when I inspect the plugs every 30-40k miles. I torque with a digital wrench to 13lbs, after back out of the compression ring seating.

per NGK: http://www.ngksparkplugs.com/pdf/TB-...1antisieze.pdf

What RPM range at Idle? Symptoms are what prompted me to change mine out, but I wished I changed them 10-15k ago.

yeah now I know

 

It makes sense to do the plugs at the same time as the 90K TB / WP job. I will do them again when I hit 200k.

 

What would be the worse thing that could happen? A plug could misfire and make the car rough? If that happened, I'd change them. I couldn't see an actual mechanical failure. Knowing Toyota, these plugs probably last to 150,000 miles.

 

Nothing bad is going to happen but the efficiency of the spark plug is pretty degraded by 100k miles. Makes sense to change it for overall health and performance of the motor.

 

Thanks for this write up. Anyone had a problem with the spark plug on the drivers side closest to the front? I couldn't remove the coil pack because the dip stick was in the way, I spent about a minute flexing and trying different angles, but I just decided to skip it and save it for last. I did the other 7 with no problems, and then the sun set at about 4:45, so it was too dark for me to even try to fiddle around. Any tricks for this one? Thanks!

EDIT: Nevermind, i was able to flex the dipstick enough to slip the coil pack through. easy enough. I did read that theres a bolt holding the dipstick in place though, but theres barely any room down there to even look/feel.

 

Thanks for the great write-up. My '05 has 117K now, so I swapped my plugs this past weekend. I was surprised to find NGK IFR6A-11 rather than Denso? I used Denso SK20R11 ($6.53 on amazon) for replacement. Plugs overall looked ok, and access was not terribly difficult (simple compared to many trucks/cars I've done); however, I did notice that many of plugs were abnormally tight all the way coming out. In my experience, you can crack a plug open and they become very easy to pull out after you've made a couple of initial rotations. But these were not the case, and new plugs went in the same way. I started with what I guessed would be the hardest plug (rear passenger), and initially concerned that it was cross-threaded; alas, it appears to be more of a carbon buildup issue. I was very careful to ensure the new plugs started correctly by hand, but was difficult to gauge final torque. I basically gently snugged to where they seemed to bottom out (could not feel crush washer), plus a small tug for insurance (maybe a 1/15th turn).

Car is running fine (initial RPM was high, but eventually settled), but no real noticeable improvement. I did observe that the throttle body is caked in carbon, so that will be my next item of maintenance.

Picture shows plugs in order (if you were standing at front of car). Many of the plugs only appeared to be dirty on one side...

 

Nice work. Both NGK and Denso were used at the factory. You should notice improved efficiency and power. Definitely do your throttle body. I clean mine every 15k because of how easy it is to get to. Don't forget about the maf sensor while you are there and the idle port on the TB. Small cover with two screws. If yours is that bad I would do it soon and buy the gasket so you can remove the whole thing to really do it right. After that, leave it in place and little touch-ups is all you need to do.

Might a mention transmission & differential fluid drain and refill. If you have not started already put that on your list. It's important.

Get yourself a torque wrench. Their cheap a Sears. With a decent set of tools and a torque wrench can save you thousands of dollars. I'm not a big DIY guy but the stuff I have done has been well worth it. Payed for the tools 10x over.

 

I have a click-style torque wrench, but my daughter dropped it as I was starting the job. Didn't want to risk over tightening due to calibration issue, so just snugged them up. I probably need to invest in a digital wrench, but it's not a tool I would use very often.

btw, do you know the gasket part # for the TB? I searched the threads, but appears everyone says they end up reusing the old one.