Cracked spark plug wires.

[Russ]

Girlfriend's 98 Mazda 626, 2.5L V6, 120,000 miles threw out a Check Engine Light a while back. Absolutely no driveability symptoms. She took it to the dealer. Diagnosis: dirty EGR valve (code 400, or something like that, I haven't seen the paperwork for myself yet). Ran fine for over 3,000 miles with CEL coming on intermittently. Last night it started running "loud" all of a sudden (again, I haven't heard it for myself). Then this morning, it started running rough on top of things. Another trip to the dealer. Diagnosis: cracked insulators on two of the spark plug wires (I imagine those were insulators - "not the wire itself, but the thick part at the bottom"). New set of wires fixed the problem. Engine runs fine, CEL stays off.
My question is this. Car was purchased at 106,000 miles in what seemed an excellent condition. Plug wires (CarQuest) were brand new. How would two of them become damaged after only 15,000 miles of service? Could they have been damaged during installation? The engine compartment was thoroughly detailed by the dealer. Could they have made old crappy wires look shiny and brand-new (is that even possible, and if so, would anybody ever bother to do it?) Or is it something else?
Thanks.

 

[cryptokid]

they probably broke then but didnt tell you about it.

 

[Gary Allan]

It depends on what quality level of wire you purchased. In the past I've had to replace so few OEM wire sets ..that I didn't even realize the symptoms. I go to buy a set of wires and "WHOA!" ..they have mulitple quality levels. I can't see anything special about 'em ..so I buy the cheapest. They lasted about a year. OEM will stay in there until about 60,000 ..once they get replaced ..it's 30k max with the higher grade.

 

[mechtech]

If a plug is old and needs a lot of voltage to fire, or if there is condensation, the spark will go right through the wire or insulator. After a while, instead of missing once in 300 times, it becomes easier to follow the short circuit, and missfires enough to notice, like every time.

 

[kenw]

quote:

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Originally posted by Gary Allan:
It depends on what quality level of wire you purchased. In the past I've had to replace so few OEM wire sets ..that I didn't even realize the symptoms. I go to buy a set of wires and "WHOA!" ..they have mulitple quality levels. I can't see anything special about 'em ..so I buy the cheapest. They lasted about a year. OEM will stay in there until about 60,000 ..once they get replaced ..it's 30k max with the higher grade.

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a bit of a generalization, and like so many, not really true. OEM may last longer than good aftermarkets, and may not. You bought the cheapest aftermarkets....what kind of comparison is that!?

I replaced Mazda wires annually with OEM until I got a set of some rather hefty-looking aftermarkets, afterwhich I never replaced them again. The OEM just got brittle and cracked very quickly.

The problem in that case was the routing took them right above the exhaust manifold where they basically cooked to death. 100% silicon jackets seemed to make the difference; they weren't the most expensive yet not the cheapest either.

 

[Gary Allan]

quote:

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a bit of a generalization, and like so many, not really true.

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Only if taken out of context. I've bought mostly NEW since 1975. At that time there was basically standard wires and OEM HEI wires. Chrysler and Ford did not opt for the ULTRA high voltage ignition that GM did. These wire failed for me due to various reason. They were ONLY replacable (AT THAT TIME) with OEM which were quite high quality. Every car that I've ever bought since NEVER had a OEM wire failure in at least 60k of use (76 Chevette, 78 BMW 320i, 78 454 C20, 1980 Toyota chassis, 1986 tempo, 92 Caravan, 99 TJ (just replaced OEM @ 91k). Now on my mother's Corsica ..the OEM's failed @ about 85k-90k. It was soooooooooooooo rare for me ..I couldn't recognize the symptoms. This was random misses across the rpm range. I got a set of wires ..problem solved.

The last time I bought any ..there was NO SUCH THING AS INFERIOR WIRES. There were no 8.8 .or 10mm ..there were no yellow fancy things. There were standard ..and HEI. So when these failed in ONE YEAR ..I was dismayed ...and found that there were many evolutions ..not only in quality ..but in cheapness. That is, you could now actually buy junk. When I was in the trade ..there was no such thing as inferior replacement parts ..only inferior manufactured vehicles.

A little more anal for your liking?

 

[kenw]

" little more anal for your liking? "

you bet....

actually, I've seen both (hence my aversion to generealities, Gary..). As previous stated, Mazda OEMs that self-toasted in 25k miles or so, and aftermarkets that were available wouldn't even FIT physically (makes it REAL hard to life test..). The OEMS were even less expensive, go figure...

that other side of the lesson was learned on a 91 2.5L v6 Camry. nearly half a dozen aftemarket sets from all the independents I could find in Houston either were too short or had the wrong end caps....form $25 to $85 per set, simple black to ricer yellow, none worked.

A $125 set from the dealer (UB Bendover Toyota) was the perfect fit and lasted at least a year or so until the car self-destructed somewhere in W Texas with a thrown rod.....

And the dealer wires were a snazzy red....