So, I went to change the spark plugs on my '95 Montero. The truck has 155k miles. Plugs and wires have 65k miles/5 years old. I pulled all the plugs and examined them closely. The old plugs are NGK Laser (double) platinum. Same as OEM plugs. 4 plugs looked pretty good. One looked bad and One looked really bad. 5 of the 6 wires showed signs of arcing. All of the wires fit loosely on the plugs. That is, I could rattle the plug in the plug boot even after the boot was fully installed. (This was determined with the plug out of the car.) I was really shocked to see the evidence of arcing. I was also dissapointed that the wires were loose. I do not know if they were loose when I installed them last time. I was going to go cheap and use the old wires until I saw the problems with the wires. I found a set at my local parts store (a real parts store, not a chain). The brand is strange (Auto Star) but the quality seemed good. Silocone wires, 7mm dia, Nice OEM style boot, and most importantly - no rattle when the boot is on the plug. The cost $49. Here are the pron pictures;



Nicely worn plug.



Badly worn plug. Notice the two flat spots on the side of the ground electrode. Notice the chunk of platinum is completely gone from the ground electrode. Also it seems like the spark eminated from the side of the center elecrode. What is going on here?



Purdy new plug (sorry for the bad focus). However, you can see the nice pointy center electrode and the chunk of platinum on the ground electrode. These are $11 NGK Laser Platinums from www.sparkplugs.com. Same as OEM. Although now I hear that the dealer sells NGK Iridiums for these applications.




Wire showing signs of arcing. 5 of 6 wires looked like this. Is this really arcing? Or what?


Image of one good looking wire.

Anyway, I am wondering what is going on with that one, really bad plug? I replaced all the wires, and the new wires fit nice and snug on the new plugs. The wires were all a bit too long (maybe 1-2in) but the still route pretty nicely. Truck started right up after reassembly. Ran fine before and runs fine now. I will check and see if mpg improves. I will not buy OEM plug wires again. I had a quote of $77 from the local dealer. Not a bad price, but after this experience I felt better with using the Auto Star wire.

Total cost;

$75 for plugs.
$50 for plug wires.
$5 for plenum gasket
$3 for anti sieze crayon. (My 5 year old applied it to the plugs)

BTW, I did not use anti-sieze last time and the plugs came out OK. A bit of grinding as I unscrewed them, but no real problems. Then again, I live in a land of no corrosion.

Wow... i've never had any problems with OEM wires. Most customers don't want to spend the extra money to replace them during the 60K plug change and they're still more than likely to make it to 120K without problems. Were the plugs in the same hole as the arcing wires?

Joel, CA

Hmmm, I guess it makes sense, but I've never used anti-sieze on the countless spark plugs I've pulled/changed and have never had issues with removing them. Never really thought about it I guess.

In hindsight the thread title was a bit harsh.



I usually do not examine things as closely as I did during this spark plug change. But, after reading all this forum stuff it starts making you even more anal about everything. The strange thing is, 5 of the six wires showed the white streaks from arcing. There was no real correlation between the evidence of arcing and the wear on the plug electrodes. I never would have looked for arcing, but I think it was you (Joel) who suggested looking for it. As far as the rattle, It was Frank that was complaining about it with his Magnecore wires that made me look for it. I was not even convinced it was a real problem until I tried the new Auto Star wires and found that they fit nice and snug with no rattle.

I am still wondering, is that white powder actually evidence of arcing? Joel, do you see arcing like this very often.

Winston -

Are you sure the white stuff isn't anti-seize? I can't tell from the photo.

[EDIT] Never mind - I see you said you didn't use anti-sieze.[EDIT]

Frank

Aah Ha. After reading about "Waste Spark Ignition systems" on other forums I found out what is happening. Half of the plugs fire with reversed/bad polarity. These plugs firing with reversed polarity will tend to cause wear on the ground electrode. That is the main reason for the platinum tip on the ground electrode, to reduce wear on those plugs. For the other three, the platinum tip on the ground electrode is not really necessary. Thus, on my car, the 1,3,5 plugs looked really good. The 2,4,6 plugs were the worst. So, the obvious thing to do is to change the polarity of the plugs at 30k miles. On these engines it is very easy since there are three coils mounted at the front of the engine. Each coil has two plug wire sockets mounted right next to each other. I wonder if anyone does this? I read that on airplane motors they tend to rotate the plugs to extende the life of the very expensive plugs. Of course, you could do that on some cars, but it would be very difficult on our trucks.

Too bad, the 3.5 liter engines with the coil packs, this trick is not possible.