Please help diagnose my spark plugs
 

I just changed my spark plugs today (2 years) and found a couple of plugs in not so great condition. I was wondering if I may ask for some help in determing what's going on inside the cylinder?


These are plugs from the left side. #1 on bottom, #2 middle, #3 on top.
http://forums.pelicanparts.com/uploa...1188869503.jpg


Now the right side is where i almost had a heart attack. #4 on bottom, #5 middle, #6 top. Four and five are covered in oil. Possible valve issues?
http://forums.pelicanparts.com/uploa...1188869697.jpg

Finally I noticed plug #1 and it's corresponding wire had some sort of green corrosion on them. Could this be from water somehow entering the chamber during washing or rain splash while driving? I had to crush the plastic in order to remove it from the wire.
http://forums.pelicanparts.com/uploa...1188869992.jpg

http://forums.pelicanparts.com/uploa...1188870127.jpg

Wow, at first I would have said oil fouled, but the plug wire looks to be corroded. I would change plugs, wires and run it. Are you seeing any oil consumption?

4 and 5 have issues. It appears that they are wet with oil on the threads. Could be valve guides (have they ever been done?), could be other things. How many miles on the car? How much oil is it using? How many miles since the plugs were put in? Does it smoke on startup or decel? You may want to do a compression and leak-down test to see wassup (not definative but can help narrow down your possibilities).

Dave, oil consumption is about a 1/2 quart every 600 miles.

Joe the valves are original.

Using about a 1/2 quart every 600 miles.

Going through the records from the previous owner I see the plugs were last changed at 107,049 on Sept 2003. I purchased the car at 111k on Feb 2005. 118k on the car at this time. Way over the two years recommended.

I do get white smoke on startup--never noticed any on decel.

Howard,

I don't see any oil on your #4 and #5 plugs ... what I do see is fairly recent carbon fouling that has come loose in a few spots. Defective spark plug cables could have caused the fouling I see.

Test results of ignition wires
 

I decided to test my ignition wires to see if they are not providing the necessary current to the plugs. Here are the results:

Spark plug connector ohm test (3k ohm per Bently)

#1 3.07
#2 3.05
#3 2.97
#4 2.78
#5 3.18
#6 2.94

I was actually happy to see #5 which might explain the carbon on that spark plug. As you can see #4 was lowest of them all?

So I reattached the connector to the wire and tested from the contact inside the cap to the end of the spark plug connector. The results:

#1 .99
#2 1.04
#3 .99
#4 .99
#5 1.00
#6 .97

So the results are:

#1 4.06
#2 4.09
#3 3.96
#4 3.77
#5 4.18
#6 3.91

I need to replace a few spark plug connectors, but should I still trying running in the dark to check for arcing or the corona?

Howard,

Those resistance values are OK ... the actual value it isn't critical at all. What I was expecting to see were a couple of 'opens' instead of good readings for #4 and #5!

Now, you need to do a 'shake test' on the #4 and #5 connectors. With a good, secure set of alligator clip-leads attached to the Beru spark plug connector ... and with meter set to continuity ... hold the connector out in front of you and shake it up and down with accelleration/decelleration motion at right angles to the body of the connector ...while an assistant attends to the meter!

Probably a dumb suggestion, but are all the plugs the same number/heat range? Just something easy to look at - sometimes auto parts stores are less than careful when dispensing plugs..

Warren's right, I would replace those two bad plug wires (and the rest if they are old).

Personally, I would be using Bosch 6's (WR-6DC) instead of those 7's as they look too warm, overall.

Double checked all the plugs and they are all WR7DC

I will try the shake test tomorrow.

Another thought - check the spark plugs for cracked insulators and continuity as well. 18 years ago I split the case on my freshly rebuilt bug engine to check for cam timing (The thing just wasn't making good power, even for a bug engine). I eventually found a brand new Bosch plug, no overt signs of trouble, that just wouldn't fire, for no apparent reason whatsoever... not likely you have two of those, but cracked insulators are not all that uncommon....

Previous records indicate these are the original wires.

member Jesset pic



http://forums.pelicanparts.com/uploa...1189392268.jpg

[QUOTE=Steve@Rennsport;3470143]Warren's right, I would replace those two bad plug wires (and the rest if they are old).

Whoever heard about just replacing two bad plug wires? Don't they come in a set? Where can you buy them individually?

Even if you could find them individually, an aftermarket set might be a better choice as well as more cost effective.

I did the shake test on 4 and 5 and the resistance held steady.

and with meter set to continuity ...

I couldn't get any continuity when stable or during the shake.

How can I get resistance but no continuity:confused: (Electricity makes my head hurt).

throw away the resistor super bosch replace with platinum plus 4s. Replace the wires and use the brackets to hold the wires from contacting the motor that seem to always get lost----my 2 cents whatever thats worth

This may seem like a dumb question but, how was the car running prior to the spark plug change? The reason I ask is, it would be nice to know what type of syptoms you were experiencing.

Second, I agree with Steve, plugs are a little on the hot side at least from what I can see in the photo.

Forgot to mention this, but oil consumption sounds pretty reasonable at 1/2 quart every 600 miles, or at least normal for a 911.

Continuity is arbitrarily defined in your VOM as a resistance smaller than [insert some value, probably < 100 Ohms]. Thus, resistance of 3 K Ohms probably won't register as continuity.

At this point, I'd probably run a compression test (while the plugs are out), put in all new wires, new stock plugs, put some Techron in the tank, and run it for a thousand miles. Then I'd have another look at the plugs. Assuming of course the car runs well with the new components installed ...