aaddpp

When changing my spark plugs today, I was a little surprised by what I found - and I am bracing for the worst . To try and keep this post as short as possible I have bullet pointed my observations:

1. Loose Plugs - the plugs seemed very loosely set in their holes - one could be hand loosened, while the other seven were VERY easy to loosen with a 1/2 ratchet (near zero effort)

2. Dirty Plugs / Plug Threads - the plugs were dirty (see photos below) with an oily sooty residue on them. This residue was also found on the threads of the plugs. On the other plugs, where a cam / plug leak was not obvious, I was thinking some of the residue was pushed up through the threads from the cylinders

3 - Oil In Plug Hole Shaft - A few of the plug hole shafts (where the spark plug cables are inserted) has some oil deposits in them - after doing some RL research, I believe the cam / plug seal were leaking.

4. Dirty Cylinder / Piston Head - Using my fiber scope, I also found an oily-sooty residue on the head of the piston as well as the walls of the cylinders. I did notice that where the piston contacts the cylinder wall, it was shinny metal -- like the piston was cleaning the residue on the cylinder wall.

5. Incorrect Plug Gap - When I measured the gap on the old plugs, I found them to be between .40 - .41 inches...my understanding is that the correct gap in the 928 is .28 - .31 inches.

I spent a good deal of time looking through the past RL posts for a similar issue, but could not find anything relating to the black oily (presumably) build up I saw on the top of the piston, the cylinder walls, and plugs heads / threads. Also, I want to add that when I ran the car, it showed no signs of any tail pipe smoke, and there is no visible residue of any kind on or around the tail pipe.

I recognize that the plug gap is an issue, but I wanted to see, based on the information and photos here if anyone had any other suggestions / paths to investigate. If anyone has any links to a thread that covers this, that would be great too - I have used every combination I can think of to find some info, but have struck out.

One more point, I have the intake and cam covers of the car for the time being.

Thanks for the help,
Dave

IcemanG17

how does the oil look?

Bill Ball

The plugs should be torqued dry to 18-22 ft-lbs -it's right on the plug box. It's hard to tell if the oil came from above or below when the plugs are as loose as you found them. Anyway, I'd clean them and the passages as good as possible, reinstall them with a torque wrench, run the car for a while and see what you find when you remove them. Most of the center electrodes look pretty good, so let's hope most of the oil came from above.

aaddpp

When I pulled the oil it seemed OK. I do remember thinking that it went from new to the obviously-run black a bit quicker than I would have expected, but did not give it much thought at the time. Unfortunately I have already dropped it at the recycling center so I can't add much more than that base observation.

Thanks,
Dave

aaddpp

Bill,

Sounds like solid advice...I guess at this point I have little to loose. I did want to add the following:

1. When I pulled the intake, I did notice there was fresh oil in the top area (at the flappy level and at the top of the air intake tubes inside the intake) - I understand this is pretty normal and the reason for the oil capture system some install. I also saw a similar coating in some of Dwayne's Intake Refresh photos, so I thought little of it at the time. At the bottom on the intake, where the air tubes meet the block, there was burned oil / sooty residue on the lower walls of the air tube. This was also apparent part of the way down the tube in the block, leading to the valves. The tops of the valves seem clean without any residue.

I was able to locate a photo of the bottom of the air tube showing the oil residue. Not the best photo, sorry.

I was thinking that possibly the oil was coming from above - via the manifold air tubes - and ending up in a cylinder that was not firing / burning properly due to the improper spark plug gap. Over time, could this lead to the condition I am looking at?

2. Car has 69K miles on it, with the initial 35K showing Porsche service records done at the correct intervals. I know that this does not guarantee anything, but I just wanted to toss in that it is a lower mileage car.

Thanks for the help,
Dave

M. Requin

Just curious: do service records show plug replacement? Someone may have run the sparkplugs down hand tight and then forgotten to torque them to specs. It happens.

hacker-pschorr

I've seen valve guides / seals needing replacement on cars with lower mileage.

blown 87

There would be deposits on the plugs in any cylinder that was burning oil.
The plugs are not showing any signs of something major wrong going on inside the cylinders.

I bet you need to do a cam cover service is my guess, that you have oil getting into the plug tubes.

Imo000

This would be my guess too. Looks like spark plug seals only leak a little too. What did the boots look like, any oil on them?

SeanR

This

Cosmo Kramer

+1 to above. If the o rings leak that seal the cam covers around the spark plug well, you will see oil pooling around the spark plug. In your case with the plugs being loose, the oil will make its way down the spark plug threads and into the combustion chamber.

aaddpp

I had a look through the service records, and could not find anything regarding spark plug replacement. I can only assume that it was done after the documented service history. Good point on someone forgetting to torque them though. When I get back in there, I will at least know its done to spec this time.

Thanks,
Dave

aaddpp

Yup, I saw that on several accounts on other vehicles as I looked into the problem. I am hoping that statistics are on my side in this case possible problem.


That's what I am hoping! Some of the plug holes clearly had some oil build up which would be consistent with the leaky cam covers. Other plugs holes did not - its these guys that are making me a bit nervous. I am in the process of getting the cams refinished, and have all the parts to do a cam covers seal refresh once I have them back to install.

When you say "boots" are you talking about the plug wires? Will have to check later today and post later.

Hoping that's the case - far easier / cheaper than the alternatives. BTW, great avitar - one of the best Seinfeld episodes written.


Thanks all for the feedback. I will post back again as soon as I have more info. For the time being I will work toward putting everything back together.

Thanks again,
Dave

aaddpp

Oooopps, one more question.

I was looking into compression / leak down tests. It seems like I could do a leak-down with the top of the engine off (cams / intake). Would it be worth going down this path to possibly identify a problem and save me having to take it all apart again if things don't improve?

Thanks,
Dave

aaddpp

Checked the spark plug boots, and they all appeared to be dry and quite clean - could not see any oil residue on them.

Dave