Spark Plug Replacement on the 2004 Prius

[berryman]

The maintenance log for my Prius says the spark plugs don't need to be replaced until the 120,000 inspection - unless you live in California, New York, Massachusetts, Maine or Vermont. If you live in one of these states, replacement is not necessary until you hit the 150,000 mile mark!?

On all my cars, I've always replaced my spark plugs every 20,000 miles - just on account of, and have always been under the impression that replacement every 20,000 to 30,000 miles was recommended to maintain optimum performance. So it's hard for me to believe that the iridium-tiped plugs that are installed in the 2004 model are going to continue to give me great performance all the way out to 120,000 or to 150,000 miles.

Have any of you out there looked into this matter? Your insights and recommendations would be appreciated.

[Jerry P]

I put iridium-tipped plugs into my Echo (same basic engine as the Prius ICE) in 2001 with about 1000 miles on it. The car now is driven by my son and has 60,000 miles, and it still runs great with exceptional miles per gallon. They were Denso IK-16 I recall and are supposed to last 100,000 miles. Based on performance so far, I think they will. They should last even longer in the Prius because of the restricted engine rpm range and the amount of time the ICE is not running at all.

These advanced spark plugs are just another thing that makes the Prius so great. Just about every leading edge technology has been incorporated into the HSD.

[quietman]

i cant see waiting 120,000 miles to change plugs. i think you would never get them out of the car engine. you could end of having them bored out and then you might as well put a new engine in the car. has anyone actually put that much miles on any plug then been able to remove it from the engine. i have no experience with toyotas except my 2002 prius which lease runs out in march 2005 and according to dealer my 2005 should be here in late janurary or early feburary

[jayman]

Well, if my 2000 GMC Sierra was any indication, it may be impossible to get the plugs out if you wait that long to do it.

My GM truck had an LS1-derived truck motor (Coil per cylinder, iron block, aluminum heads, etc). In 2002 I decided to change the plugs after getting a misfire diagnosis due to a tank of bad gas.

I just about gave myself a hernia trying to get the plugs loosened. I'm still surprised I didn't break a plug off or damage anything in the process. Once loosened, I still had to use the socket, as the plugs turned VERY stiffly and gave off a horrible screeching sound.

The plugs had obviously been put in "dry" with no antiseize material applied to the threads. There were flakes of aluminum on the plug threads, that was a BAD sign!

I applied Loctite Nickle Grade anti-seize to the new plug threads and properly torqued them down. This summer, I thought I'd check one of the plugs to see how clean they were.

The plugs came off very easily, and the electrodes looked very good. So I dabbed on a bit of Loctite Nickle Grade and properly torqued them down again.

It seems a bit difficult to get to the plugs on the Prius, as you have to unplug the coil and remove that first. Without a shop manual to guide me, there is no way I'd attempt it.

[Jerry P]

When I put the plugs in the Echo, I used an item called Fel-Pro C5A on the threads to make sure they will come out. It's a good idea to use something on the threads, especially with aluminum heads on the engine.

[jchu]

I remember listening to Car Talk a number of years ago about this kind of issue. Their suggestion was not to necessarily replace the plugs but to loosen them and then retighten them every 30,000 miles or so just to prevent them from getting irrreparably (?spelling?) stuck/welded to the engine block.

[DaveG]

<div class='quotetop'>QUOTE(jchu\";p=\"60267)</div>

I remember listening to Car Talk a number of years ago about this kind of issue.  Their suggestion was not to necessarily replace the plugs but to loosen them and then retighten them every 30,000 miles or so just to prevent them from getting irrreparably (?spelling?) stuck/welded to the engine block.[/b]

Hmm... That's a very good idea... Will have to put that on "my list of things to do", but 30,000 miles (48,000km) is a ways-off still

Dave

[DanMan32]

While you're there, might as well check the gap and apply anti-seize.

[longshortofit]

I also have a 1999 Chevy Silverado Pickup with 5.3 liter v8 engine and I replaced the plugs at 140,000 without any problem. Plugs still look good, but with a recommended change at 100,000 miles, it was time.

The Prius with less engine running time over a v8. It is nice not to change plugs very often. 120,000 would be the earliest, unless you have a rough idling engine. Then that could be a plug wire also.

Steve ~~~_/)_~~~

[DanMan32]

No plug wires in Prius. Each spark plug has its own coil on top of it.