Spark plugs

parnowel

Can you tell me when do you know when your spark plugs needs to be replaced? (i have 167 000km and they have never been changed)

swschrad

I think in terms of miles... and have to convert... but I think that by 80 Km (50,000 miles down here in round figures) you should have changed both wires and plugs just on general principle.

yes, even double platinum plugs. there is enough deterioration that under severe conditions (towing, 30 below F, making a sharp turn in reverse just above idle) there will be some loss of power noticeable to the driver.

course, I'm just cranky about being sure I get back from where I go....

nippononly

100,000 miles, and if you have iridium plugs like most cars from about '98 on, with the vaunted "100,000 miles between tune-ups", then you are just about due for them right now.

If they are copper or platinum plugs like in an older model car, then yes, you should have changed them long ago, and I wish you the best of luck in changing them now.

leadfoot4

that spark plugs that have been in place for that long may not want to come out...at least not very easily. In fact, they may become "lifetime plugs"!! LOL!

gsleve

a little WD-40 in that area let it set over night and it'll work it's way through and if you first try tightening the plug first, in this way you may be able to facilitate their removal, coupled with spraying a little more of the lubricant along the way

swschrad

but instead of "tightening," I would have said, "try to bump the plug further in about 30 degrees or so as the socket wrench turns to crack the rust if it won't come out. if you work harder on it than that, you can occasionally break a plug off, and then you need serious assistance. if it does move, pour on more penetrating oil, take a half hour off, and try removing it then."

fleetwoodsimca

If the plugs were properly torqued at installation, and you do the work now at room temperature in the engine, I'd forget about being worried over seizure and just remove them and replace them. If they were overtightened previously, then problems are more likely. Do NOT remove long standing plugs from an engine when the engine is hot. Strip threading is far more likely, and who wants to work on a hot engine, anyhow?

swschrad

if you have some freeze spray (note, most I have seen is freon-based, so they won't sell it to you any more unless you have your sales tax permit in hand) it can do wonderful things on "frozen" parts rusted together.

for instance, on that ONE plug that simply won't come out no matter what... with a warm to the touch engine only, soak down the PLUG ONLY at its socket head with freeze spray, it might work wonders. don't try on an engine more than warm, you can crack it.

it did wonders on a seized up cast-aluminum Atwater Kent model H speaker assembly... blew off a couple ounces of freeze spray on the frozen adjustment ring (3" diameter) which had previously been soaked up in Liquid Wrench... took a CJ-12 Vise-Grip (tm), and it......... came......... off......... justlikethat. the guy who posted how to rebuild these 1925 speakers broke his all to hell and gone, had to do a lot of work with grey JB-weld.

zoomzoom626

Can someone tell me which of the two above mentioned brands makes better iridium plugs. I did some shopping on the web and found that NGK iridium are almost half the price of Denso's iridium plugs. So if there is no significant difference I would rather spend $50 then S100 for plug replacement. I drive 2000 mazda 626 LX-V6.
Thanks

fleetwoodsimca

I sincerely suspect you can choose to buy NGK or DENSO-- your choice. You might well be able to go further yet, and elect to not use iridium plugs at all.