Spark-plugs

The manual calls for iridium. Since they last at least 100,000 miles, I would not spend the extra for the laser version. I use what's specified in the manual.

 

Use the p/n provided in the Owner's Guide, not a substitute or other "will fit" plug. Don't forget to correctly torque them and apply dielectric grease LIBERALLY to the boot interior and exterior.

 

NGK has laser iridium spark plugs and IFR5T11 is designated as the correct plug for Prius. I do not suggest you use a lesser plug from the NGK line. (The original equipment NGK plug was replaced by IFR5T11.) Amazon has those plugs in a set of 4 for $26.70.
NGK Spark Plugs

Or you could install the correct Denso iridium plug which is SK16R11. The price is a bit higher, $30 for a set of 4 at Amazon.
Products | Spark Plugs | OE Type | Iridium Long Life

Basically, you are looking for an iridium spark plug which has iridium at the tip, and a platinum disc on the ground electrode. That minimizes the spark plug gap wear, thus enabling the plug to last 120K miles in normal service.

 

Torque is 13 foot/pounds according to Repair Manual, I'd assume with dry threads.

 

Yes, that is correct, Toyota recommends not using any type of additional anti-sieze.

 

Yup, adding ANYTHING to the threads changes the actual applied Tq, don't do that.

I do not want to hear about anti/never seize and all the presumed reasons to use it. Fact is, if quality (read: OEM specified) plugs are used and they are changed in accordance with manufacturer recommendations, there is no need.

 

I just changed my spark plugs last weekend, but I used Denso's Iridium IK16TT. Do you think this will cause a problem? I didn't check the gap but I think they came pre-gapped to 0.04" or 1.0mm. Car seems to running better, might be getting slightly lower mpg but that might be the weather.

 

Those plugs may not last 120K miles; besides that issue they should be OK since the heat range is correct.

 

Also, just so you know, iridium plugs come pre-gapped and trying to change the gap can damage them.

 

Ok thanks, I was worried that they might not work, but I will check them every 30k to make sure they are in good condition. I learned my lesson to check on here for the part number.

 

I've read this, from either Denso or NGK, forget which. Optimum gap is part of the design. Also, sandblast or other abrasive cleaning of used plugs should be limited or avoided: carb cleaner and a toothbrush will do.

 

Correct, I can assure the group that no OEM gaps plugs prior to installation. They just pull them from the "box" and install. Decades ago, when a plug was used on multiple different engines from various manufacturers, the service replacements did need to be checked and often adjusted for gap. This is no longer the case for most, if not all, automotive applications.

I would add that if a removed plug is "dirty enough to warrant even the thought of it needing to be cleaned", STOP. Fix the cause of the oil, excessive fuel, coolant, overheating or whatever and DO NOT clean the plugs used in any modern on-road engine.

 

Still, I think even with optimum conditions plugs will look a little grungy if you pull them halfway through their service life. And there's no harm in going over them with a toothbrush and a little carb cleaner. Especially with the PCV and (new to 3rd gen) EGR systems dumping into the intake manifold, by design.

 

PCV has been there since 1969 and EGR since 1975, neither make the plugs worse for wear. The single biggest depositor is fuel contaminates in a modern engine in good repair.

Below are two plugs from a late '90's (dirty by Prius standards) V8, one new and the other having ~85k on it. The "experienced" plug is completely, 100% serviceable, but once you go to the work of removing them I think it is silly to re-install used ones (except if part of some diagnostic check).

 

Between the high price of everything up here (plugs close to $20 apiece), my abundance of spare time, and a (possibly irrational) propensity to keep things pretty, I'm inclined to pull them once, about half-way along, an hit them with carb cleaner. Different strokes.

I think with second gen you don't have to remove wipers, their motors and cowl for access? Look what the engineers have foisted on third gen'rs:

 

Overly maintaining is GOOD!

 

Jerry, is that right 87 mpg???? what am I doing wrong, or do you have a Prius +?

 

Ok all, I just replaced my plugs at 130K (mostly highway). I did use anti seize..... oops. I did crank them down to 13 ft/ lbs. Should I go back and wipe what I can off the plugs or? It won't really be that much extra work, as I need to replace the coil pack bolts. I read/ watched something that stated that both the coil pack bolts and the plugs should be torqued down to 13. I was doing that with the coil pack plugs and then "snap". I thought I was going to have a heart attack. My mind was "Oh my God, I just snapped the bold off deep in the head cover!" Luckily, one bold extracted and the top part of the bold was barely holding on to the bottom part. Then I started to remove the other ones to see if I screwed up. As I was loosening another bolt "Pop". Again, feelings of impending doom. The bolt did completely break in half, but there was enough sheered bold sticking out of the head to unscrew it with pliers. I got soooooooo lucky! I am not too sure about the 13 ft/lbs for the coil pack bolt. However, it might be just, but with new fresh bolts. I think with the prolonged heat of the engine and age of the metal it was a set up for disaster. Called the Stealership and ordered 4 more bolts, currently using some 8.8 steel Home Depot specials $0.53 a piece. $2 at the dealership, but I am not sure if the zinc plating on the Home Depot ones do some funky stuff against the aluminum engine head.

Anyone know the true specs for the coil pack bolt torque? Also, what about my anti seize compound, should I remove it. A couple of my plugs were really crusty and didn't really want to come out.

 

The torque for the ignition coil connectors is 80 in.*lbf, so that is 6 ⅔ ft.*lbf. Probably explains why you're breaking 'em.

I wouldn't bother, now they are in. Usually you back off a couple of ft.*lbf when you use anti seize. The torque for the spark plugs.
13 ft.*lbf. (Maybe you got that mixed up with the ignition coil connectors.)