Spark plug

2 hours, give or take, depending on your experience and skill level.

 

I agree with Bisco, DIY taking your time, 2 hours.

If you are asking about shop "book time", I do not know.

 

I haven't done it yet, but it's WAY easier than on previous generations. Just remove the plastic rivet at the passenger (in LH drive cars) end of the plastic cowl over the plugs. Then bend the cowl out of the way.

 

Yeah I think with 4th gen only partial removal of the trim at bottom of windshield is needed. Or hey: take the wipers and cowl completely off, and install anti-rodent mesh on the cabin air intake?

Attachment from Repair Manual shows full removal (I think...), which may be overkill. It also notes spark plug torque as 15 foot/pounds. That's presumably with clean/dry threads; if you use anti-seize I'd recommend to apply, wipe it off (just leave residue), and reduce torque to around 12~13.

There's also a torque spec for the hold-down bolts on the ignition coil assemblies. A couple things to note with that:

1. These bolts are purely hold-down, locator bolts. Just snugging them securely will do, without a torque wrench.
2. If you do use a torque wrench, the torque spec is in INCH/pounds; there's been more than one report here, novice mechanics dialed in the value, in foot/pounds (12-fold increase), and snapped the head off the bolt. Then the fun begins...

Socket size for the plugs is likely 14 mm, or 9/16" in a pinch? You'll need to use extensions, and if you got a spark plug socket with rubber insert to grip the plug, I'd recommend to tape the socket to the extension, to avoid possibly leaving the socket down the tube with the plug.

Those plugs should be gapped correctly, and I believe Denso cautions to not attempt to adjust the gap. Also, if reusing plugs, don't sand blast, just use something like a brass or nylon bristle brush with carb cleaner.

Also, the excerpt puts install section ahead of removal. This is because Toyota apparently didn't create a pdf version for gen 4, and the creator of this pdf manual just let everything sort alphabetically.

 

Unless you are having issues, Iridium spark plugs in a 2016 Prius should be good until 2026 (10-years) or 120,000 miles.

 

Just editorial: the time interval for spark plug change is 12 years. Attached spreadsheet is summary of the US event-by-event schedule in the warranty and maintenance booklet.

 

fabulous, i have another 2+ years

 

When I looked at mine, I didn't see any reason to remove anything except that plastic rivet. I won't need to test that idea for another 50k miles or so.

 

I've done this twice to date @ 240k on my 2016. Agreed, two hours sounds right for a careful first time. A few notes from experience:
1) Confirm part number of your new plugs. 90919-01298 is the correct p/n for Gen 4 Prius 1.8. Dealer handed me 90919-01289 plugs for the 2.5, an easy "dyslexic" mistake I suppose.
2) I've found it helpful to fully remove wipers + cowl to pull the long coil assembly out carefully and not bend. It's also a good opportunity to clean out any leaves and dirt around the cowl. The rubber shields at each end of the cowl are a bit fussy positioning correctly.
3) Before removing wiper arms, mark the resting location of each wiper on the windshield with some masking tape, saving you having to think about that later.

 

120,000 miles or 10 tears, whichever comes first

 

even better

 

Depending on how much they cry, it might be the miles.

 

12 years is coming up for me, November 08 of this year. Will very likely revisit the EGR and intake too, at same time. I better not disclose the kms...

 

I knew somebody who probably wouldn't shed 12 tears in 120,000 miles.

 

Pour la Prius 4 , c'est 200 000km pour changer les bougies.
Sur la mienne de 2017 , je suis à 195 000 km et toujours d'origine.

 

You crack the 100 k km mark yet?

 

Just ticked by 93k kms. Between retirement, weather and COVID the car’s seeing very little use. Nearly all our groceries are bought within walking distance, and using Amazon too.