Idle Problem Solved - Carbon Tracking

[twr]

Hello all,

Just thought I would share this. I have been fighting a slight miss at adle and some power loss as of late and have had trouble tracking the culpret down. Last night I decided to pull the intake off and re-inspect my wires and plugs a little more closely. I found my number 2 plug to have a carbon track on it and upon closer inspection of the plug boot foot a matching burn mark. I took some pictures and I though I would post them here for your viewing pleasure.

#2 plug, I hi-lited the carbon track (spark path)

This is the corresponding plug boot. You can really see the path the spark took and the blue looks like a smoke residue from arcing.

I have not had a chance to replace the plugs and wires and take it out for a spin to see what the improvement is. Hopefully tonight I will.

<small>[ February 12, 2003, 12:21 PM: Message edited by: twrsho ]</small>

 

[shojuan]

How old are those plugs and wires?

 

[twr]

Plugs have less then 12k miles on them. Wires are about 1 1/2 years old (replaced before the plugs)

 

[sdpatt]

That is an excellent example of the arc tracking phenomenon. It is hard to see unless you know what to look for. I also had a problem with arc tracking - also on the number 2 cylinder - with relatively new plugs. The picture of the affected plug is shown below. I believe my case was from constant pinging due to hot, dry weather and an overly aggressive spark curve from the Superchip. The plug looks to have been overheated by the pinging as eveidenced by the browning of the insulator. The misfire got progressively worse during a 450 mile trip until even steady throttle at highway speeds would cause a misfire.

<small>[ February 13, 2003, 12:55 PM: Message edited by: sdpatt ]</small>

 

[twr]

Scott,
Similar situation here. Started as a slight miss and had gotton progressively worse. Yesterday I was starting to get a small back fire when pulling away from a stop lights. Decided I'd better re-examine my plugs and wires.

Note: I wiped the spark plug off, what your see is the remaining carbon.

BTW - Any idea if this is plug related or wire related??

 

[sdpatt]

Electricity will take the path of least resistance. Literally. Since the current is bypassing the plug's gap and not shorting from the wires to the engine, I guess that this is a combined problem both inside the combustion chamber and in the insulation and sealing of the spark plug boot.

There are certain conditions inside the combustion chamber that make if very tough to get a spark across the small gap. I believe that the overheated plug created by the preignition from the hot, dry air complicated my situation. If there is another path that is easier to travel, the spark will take it. This is where contaminants such as oil or moisture in the spark plug wells can provide this path on the outside of the plug. Clean, dry plug conditions and the use of dielectric grease can go a long way towards preventing these exterior spark travel paths.

Conclusion: low resistance conditions at the interface between the spark plug and the spark plug boot in combination with high resistance conditions inside the combustion chamber allowed this to happen.

Prevention: Keep the oil and moisture out of the plug wells and use dielectric grease to provide a moisture and electrical seal between the spark plug and the plug boot.

 

[shojuan]

I'm having a mysterious hot running problem with my SHO. Only have 6K miles on my plugs and wires but I guess it's worth pulling at least my front plugs to have a look see. I used plenty of dielectric grease.

 

[twr]

sdpatt:
Electricity will take the path of least resistance. Literally. Since the current is bypassing the plug's gap and not shorting from the wires to the engine, I guess that this is a combined problem both inside the combustion chamber and in the insulation and sealing of the spark plug boot.

There are certain conditions inside the combustion chamber that make if very tough to get a spark across the small gap. I believe that the overheated plug created by the preignition from the hot, dry air complicated my situation. If there is another path that is easier to travel, the spark will take it. This is where contaminants such as oil or moisture in the spark plug wells can provide this path on the outside of the plug. Clean, dry plug conditions and the use of dielectric grease can go a long way towards preventing these exterior spark travel paths.

Conclusion: low resistance conditions at the interface between the spark plug and the spark plug boot in combination with high resistance conditions inside the combustion chamber allowed this to happen.

Prevention: Keep the oil and moisture out of the plug wells and use dielectric grease to provide a moisture and electrical seal between the spark plug and the plug boot.

Iteresting thing is, I used di-electric grease on all the connections. I must have had a piece of foreign material in the boot (hair or strand of fabric) or a bad plug insulator.

 

[shojuan]

twrsho:
Iteresting thing is, I used di-electric grease on all the connections. I must have had a piece of foreign material in the boot (hair or strand of fabric) or a bad plug insulator.

Hmmm. Now I really ought to take a look at my plugs and wires.

BTW, off-topic but Scott you might be interested in these: http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33627&item=2403354822&rd=1

 

[sdpatt]

Thanks Rick. I have now been in touch with Adam.