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Sherlock Ohms

Shorted Spark Plugs Cause Misfire Code

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Ye Ole Professor
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Iron
Ah yes!
Ye Ole Professor   2/22/2014 7:57:51 PM
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They just had to move the production of those plugs from the little town I live in with the big almost empty factory to Mexico!


You're not the only one who's had a problem since the "move"....

bobjengr
User Rank
Platinum
MISFIRE CODES
bobjengr   2/22/2014 4:45:40 PM
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It's always interesting to me that virtually no company produces six sigma data to indicate where they "stand" relative to production and the quality of their product.  As you all know, six sigma designates 3.4 failures per million products.  We know that most companies lie somewhere between four (4) and five (5) sigma when it comes to off-quality.  That's in-house quality with few products being packaged and shipped to retail establishments.  This seems to be a fairy tale with some suppliers today.   Excellent post.

TJ McDermott
User Rank
Blogger
Re: Just Coincidence?
TJ McDermott   2/19/2014 9:15:22 PM
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I'm with Turbineman.  3 times is enemy action.  Either that, or we let you pick lottery numbers.

wawaus1
User Rank
Iron
spark plugs
wawaus1   2/8/2014 9:40:57 PM
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With spark ignition engines I try to always use NGK plugs, I have had problems with Champion and Bosch in the past.

Hopefully those problems are all in the past since we are currently all Diesel and plan to stay that way!

William K.
User Rank
Platinum
Re: Leakage Check
William K.   2/7/2014 10:08:46 AM
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I have used both a fairly good VOM to check plugs for fouling, and also a 3 1/2 digit DMM. The serious short circuits and fowling show up quite well even at a low voltage, perhaps 1.5 volts for the VOM and about 3 volts for the DMM. The test is very simple, but it does demand access to thye top terminal on the spark plug, which is a true pain on some engines. Checking back through the plug lead toward the distributor cap is a less reliable way to check for cap problems, since mostly cap failures are of the arc-over type, not consistent short circuits. But pulling the cap will allow checking the plug lead, which will detect open circuits that may arc across and allow the plug to fire weakly. And the shorted plug test can also be done from the cap end, although the combination of a shorted plug and an open cable will not be detected.

I once had a problem with an aftermarket ECM that was caused by rust inside the encapsulated module acting like a varistor on the switched coil lead. So I could get a spak, but it was not strong enough to fire the plugs consistently. That one took some detective work, and a new module, to find.

tekochip
User Rank
Platinum
Just Because it's New.....
tekochip   2/7/2014 9:30:45 AM
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I was working on a motorcycle and one cylinder wouldn't fire at all.  Finally I tested the brand new plug and found that it was shorted.  After that I developed a new mantra; "just because it's new doesn't mean it's good."


DB_Wilson
User Rank
Gold
Leakage Check
DB_Wilson   2/7/2014 9:09:31 AM
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Thanks for posting the information on the plugs.  It is timely as I am planning to change the plugs in my 1995 Aerostar.  As difficult as it is to change plugs, I want to find any problems before I install the plugs.

What test voltage and instrument did you use to test the plugs?

Turbineman
User Rank
Gold
Just Coincidence?
Turbineman   2/6/2014 1:29:49 PM
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With the original issue, you've had no less than three incidents related to the same cylinder. This seems to go beyond mere coincidence. You might want to do a bore scope check of the cylinder and valves.

Years ago, I had the same experience with Champion spark plugs.  Of any box of 8 plugs I bought, I had to return at least one plug.  Haven't had problem with them in last 25 years, mainly because I haven't used Champion plugs since then.

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