In researching spark plug replacement, I noticed that some had a bit of a challenge unplugging the drivers side plug wiring from the harness. I found it very easy to merely remove the two bolts (10mm socket) that secure the plastic that houses the wiring harness. Now there's no need to unplug--merely lift it out of it's plug hole. I bought my Prius used, but from it's records, it appears to have had it's original plugs at 172,000 miles. The old plugs have gaps around .003 to .004 inches wider than it's replacements. The car was driving fine, but I'm more comfortable with new plugs, especially after 172,000 miles.
Wow! A bit long for plugs, I'd say. Glad you replaced them, and if I'm not mistaken, your picture indicates that you indeed replaced them with iridium tipped (and DENSO) plugs. Well done. I read this thread title thinking it was going to be a question "should I replace them now?" haha
They were a bit tight, but not overly bad. From its records, I believe that the plugs were last pulled at 124,000 miles. (Owner declined to replace them.)
I have an 06 with 237k that have the original plugs in it. I bought the NGK laser iridium plugs due to there 120km life expectancy. I will be replacing the plugs tomorrow. Wish me luck! I love my car! If I set the cruise at 60mph I have driven 200 miles at 56mpg.
Have you checked you've got the right socket size? Assuming the new plugs are the same size, test on it. 3rd gen is 9/16", that was new for me, was expecting 5/8". Yeah, good luck extracting the old ones.
