Spark plug replacement - tools needed

What is the condition of the old Iridium plugs like at 100,000 miles?

I just changed the OEM platinum plugs on my 2002 Ford Explorer at 60,000 miles and they were all out of gap specification by 0.007" (should be 0.052" - 0.056", all were at 0.063"). According to the owners manual on the Ford these plugs should be good for 100,000 miles but given their condition at 60,000 miles there is no way they would make it. An interesting aside, the Ford also had different plugs in each side of the engine, neither of which were the double Platinum spec'd in the manual! Great QA there Ford.

 

This is intentional. The double Platinum plug model is utilized when you replace the original equipment plugs.

The original equipment plugs are different on each bank for the following reason: The Ford ignition system fires two plugs at once, using one center-tapped ignition coil to fire both plugs. This saves some minor expense with the engine ECU.

However, the result is that the voltage polarity applied to one plug is opposite that applied to the other plug, with respect to vehicle ground. Hence the plugs installed on one bank need to have the platinum tip on the center conductor, while the plugs installed on the other bank need to have the platinum tip on the ground conductor.

Prior to buying my HiHy, I owned a 1997 Explorer XLT V8 AWD and replaced the platinum plugs at ~90K miles. What a PITA; I had to remove both front tires and access the plugs through the front fender liners. Scraped a few inches of skin off one arm when a spark plug wire refused to disconnect from the plug, then suddenly let loose when I pulled hard... I had to replace all of the spark plug wires since the connectors were in bad shape. Too bad Ford did not use dielectric grease on the connectors...

 

My FJ Cruiser also came with different brand plugs from the factory: NGK driver side vee, Denso passenger side vee. Dealerships replace with just Denso's. I used NGK and it works fine

Could be just a supplier agreement in the case of the FJ

 

Thanks Patrick - I did a Google search on this issue but you were the only one with an explanation! I thought it odd that one side had the Platinum on the center and the other on the ground side. I replaced 'em with double platinums which should last at least another 60,000 miles.

Given the troubles that some plugs have in aluminum heads coming out after a long period of time, I do not think I'm going to let my Prius go 100,000 miles on the OEM plugs. Most likely I'll pull 'em at 80,000 miles or so and replace them with another Iridium set.

Rumple

 

This is a good idea. I removed the plugs on my 2004 at 30K miles for inspection (and to make sure there was no water in the spark plug wells), put a bit of antiseize lube on the threads, reinstalled them, and cleaned the surface dirt off the tops of the igniters.

 

I feel silly asking this, but...
Do the Denso plugs come pre-gapped, or did you require a gapping tool during your work?

 

No need to feel silly, this is a very reasonable question as the spark plug might be used in more than one engine model.

I set the gap to 1.0 mm. The factory-set gap is bigger than that.

 

Thank you for the reply.
I am curious why you chose 1mm.

 

The spec is 1.0 to 1.1 mm, so I set the spark plugs at the narrow end of the spec. Presumably they will remain in spec longer, by starting at 1.0 mm.

 

Thanks for the info.
I just got in from changing my plugs.
I discovered that it is also a great time to replace the PCV valve since the wire harness is tucked out of the way.

 

Your directions are quite precise - made it an easy 1/2 hour job. The "resistance" is not from residue but is the compression seal seating. Recommend Advanced Auto Parts magentic socket #80546($10.29) which has a swivel extension as part of the tool. Add a 3" extension to this and it's the perfect length. My '04 Prius had 130K when plugs changed; wouldn't recommend going any farther - they were very well eroded.

 

Nice writeup on changing plugs.

The only thing I would add from my own experience is to avoid platinum plugs because the pucks sometimes fall off and to always check the gap because sometimes the factory set gap is not correct. I tend to always make the gap a bit tighter than factory settings just for reliability...

 

I think amazon.com is having good price for spark plugs.

 

Takes max 10 min to do it

 

my dealer told me that i need to have my spark plugs relpaced, which I plan on doing myself once it gets warmer. He also mentioned that I need new spark plug wires. Does anyone know the oem part for the wires?

 

Prius does not have "spark plug wires". Each spark plug has its own igniter, which sits directly on top of the spark plug. Hence no high voltage wiring is needed.

 

Did he tell you

.

 

FL8, that guy looks nothing like my "Service Advisor" aka salesman. My guy looks slicker.