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Old 11-11-2008, 12:32 PM   #1
theleveler
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Default The Autolite Spark Plug of Death!

Got a story I resolved yesterday and thought I'd share...

2003 NA Baja (70k miles). Kickass car but I wish I got the turbo. My biggest issue when it comes to car maintenance is that I'm lazy to fix (or even notice) issues that creep up over a length of time, as opposed to an instant change.

I replaced the spark plugs about a year and a half (20k miles) ago with Autolite's equivalent to the NGK 5463's that come recommended for the car, figuring they're all the same (and I'm still not sure that the plug is to blame). Things have been fine until about a couple months ago when my car started developing a slight hesitation. This was accompanied with an intermittent buzzing static on certain FM stations coming through my radio. A few weeks later and both symptoms got a little worse, while I remained lazy. The buzzing concerned me and, thinking I might have a bad ground, I tested the electrical system which indicated that everything was OK, with the exception of my battery going bad (which was reasonable as it was starting to get the white powder around the top). Around this time, I noticed the misfiring sensation (sudden shake and judder to the side). For a while it remained pretty intermittent and, suspecting a long course of troubleshooting due to the FM noise, I remained lazy until the misfiring got really violent and the CEL FINALLY came on. DTC was a P0301, misfiring 1st cylinder. Still expecting a long course of troubleshooting I started where one should... replace the sparks.

2, 3, and 4 were fine. Plug 1 had rattled a little loose (bad compression clearly... there was soot all over the boot of the plug). Stupid me had probably not tightened it enough. Also the little copper boot that goes into the plug wire was broken off and stuck in the wire. I cross threaded a screw into the little thing to yank it out of the spark plug wire, and had found that it had lost all of its tread. I thought that was strange. Then I rotated the plug in my hand... The center electrode was loose, and (when tilted) would slide back and forth from having a considerable gap, to making contact with the negative prong. I can't remember ever having a spark plug with such big structural failure without having any indication of detonation on the ceramic.

Replaced all plugs with NGK 5463s, cleaned the wires out, and cleared the computer. The misfiring was gone. Had to readjust to more active breaking since I had apparently gotten used to the excessive engine resistance. The surprise was that the Radio static was gone! I had no idea that bad ignition noise like that could be heard in the radio!

Anyone ever have bad spark plugs make themselves noticeable through the radio before?


EDIT: Heh.... Just read the FAQ on spark plugs... evidently it's not unusual to hear noise in the radio. I'll have to read more about it...
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Last edited by theleveler; 11-11-2008 at 04:51 PM. Reason: Found more info
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Old 11-11-2008, 02:36 PM   #2
soulhassorrow
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denso or ngk are the only plugs i would use.it's a good thing the problem was fixable!!!
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Old 11-11-2008, 09:09 PM   #3
RaceFaceXC
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the plug almost certainly failed due to becoming loose (not being torqued properly). I have seen this EXACT thing happen on other engines, and all 3 times it was due to the mechanic not tightening the plug. (one time it was me, being in a hurry) On one of the plugs, some of the ceramic came out into the cylinder and beat the hell out of the piston top/CC ceiling and broke an exhaust valve on its way out.
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Old 11-12-2008, 12:03 AM   #4
Subaru_Pork_Wagon
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Had one do that before and blew oil all over the inside of my crank case.
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Old 11-12-2008, 07:22 AM   #5
RaceFaceXC
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oil all over the inside of the crankcase? Oh No! But seriously, thats where the oil is supposed to be.
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Old 11-12-2008, 11:31 AM   #6
theleveler
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Yeah I bet it was due to it's looseness. I paid much more attention to tightening them this time... particularly because the tightness seems to go through plateaus, where it will get a little tight but still turn free for another turn.

I ordered some new spark plug seals too as I can see that the one in cylinder 2 has a little bit of seepage, although nothing too alarming. How much of a PITA is it to replace those? And is there anything else I should do while I've got the valve covers off?
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Old 11-12-2008, 06:38 PM   #7
RaceFaceXC
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It sounds like you are just tightening the plugs with a wrench until they feel "good and tight". I call this the german torque wrench... "goodntight". you should always, always, always torque spark plugs with a torque wrench. the washer that is used also acts as a gasket and requires a minimum torque on the plug to compress and seal fully. (technically you are supposed to replace or anneal the washer anytime you remove or loosen the plug) it also is threaded into an aluminum head (should have a steel helicoil) and over tightening could potentially damage the threads or pull them out. so getting the plug to the correct torque is necessary to prevent combustion gas leakage and prevent damage.
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Old 11-13-2008, 12:40 AM   #8
kingbobdole
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Just a note.. Autolite plugs are total crap... how much did you save, like a dollar a plug? oh boy $4 to use the wrong plugs. Always use OEM stuff. When the ignition system was made for the car, they designed it to function best with a specific plug... in Subarus it's always NGKs. Densos are nice, but still not the right plug, and don't even get me started on Bosch.

Now you get a jeep or BMW or what have you and you use different plugs. The BMW wants Bosch plugs but the jeep, Champions. Right plug for the right car. always.
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