NeedPorscheSpeed

Oh boy...

I recently took my 968 on a two hour trip to Birmingham. The entire way down there, I marveled at how comfortable the car was on the Interstate and how enjoyable it was to drive. I was thinking about how I had not had any maintenance troubles since I had bought it in July. I even said to my dad, "I sure have had good luck with this car, haven't I?" Well, little did I know that the end of the honeymoon was near...

On the way home from Birmingham, just as I was getting off the Interstate, the car started coughing when we stopped at a stoplight. At first I thought it was only a rough idle, but as I continued driving home, the car started backfiring. It seemed to be going on 2-3 cylinders, so I immediately suspected the ignition system, probably the spark plug wires.

When I was able, I checked under the hood, and to my surprise, the sparkplug harness (ignition cable) to cylinder 1 had come unseated. Great, I thought, I'll just press it down back into place, and all will be fine. Not so fast, but nice try, the 968 said... Much to my chagrin, as soon as I started the car again, the sparkplug harness to cylinder 1 popped off. (It didn't just pop off, actually, it came off with great force, making a "clang" when it hit the hood.) At this point, I decided to check the other plug harnesses, and when I removed the one from cylinder 4, oil was all over the sparkplug... I have since cranked the car a few more times, and every time, it blows off the sparkplug harness from cylinder 1 immediately and forcefully. The car does stay cranked, even with the sparkplug harness popped off, but it shakes violently upon startup, and of course it has greatly diminished power.

This is as far as I have investigated so far, as I have been swamped with work. I parked the 968 and have been driving the 1989 951 as my daily for the past week. I have wanted to post this information about the 968's "symptoms" for over a week now, but have just now been able to come up for air from my busy schedule. (Well, I did have Saturday free, but that adventure is for another thread, when I get the chance to recap it. )

Any advice, insights, or similar experiences would be greatly appreciated. Thanks in advance!

my87944s

Well, if the valve cover is anything like that of the 944S (which I think it is), you might just need to replace the gasket rings that seal the spark plug chamber (wrong terminology but I hope you get the idea). If those rings are bad and allowing oil onto the spark plugs, it would result in a bang strong enough to blow the spark plug boot out. Each spark plug chamber has a rubber gasket that seals the valve cover against the head. When I just put mine back together today, I replaced all the gaskets (including these). The entire process took about 30 minutes and the kit cost around $60.

Rock

Oh no

I feel for you man and I hope its an easy and inexpensive fix

NeedPorscheSpeed

Thanks for the advice my87944s. A friend of mine had told me that it was probably the seals, but wasn't sure if that could be responsible for the spark plug harness blowing out of the socket. Thanks!

Thanks, Rock! You da man!

Luis de Prat

Jonathan, if it's clean oil I agree with my87944s. I've done the same repair to my 944S2 cab and the only caveat is to be very careful not to overtighten the cam cover allen head bolts, or you can snap them and end up having to use an easy-out on the cam tower, which is not fun!

Check with the 968 people for replacement parts, but essentially you'll need a valve cover gasket, the O-rings mentioned, and the rubber washers for the allen head bolts. Not sure about the 968, but on the 944S2 there was a lubricating "J-tube" that was originally plastic and had to be replaced with a metal one because the plastic ones collapsed and made an oily mess. Probably superseded for the 968, but I'm not sure.

If you have a precision torque wrench for small applications it will give peace of mind when fitting those cover bolts back on.

As for the spark plug connector popping off the plug, this is just a guess, but it's possible that the excess oil may have loosened the plugs or contaminated them to the point where this would happen.

Good luck!

Zero10

If the boot actually pops off, and bangs on the hood, I would check how tight your spark plug is....
Sounds like you're losing compression around the spark plug, and since the boot somewhat seals (usually) the hole, it would build pressure, until the boot pops off.

As for the oil, the previous posters are probably correct. Is there oil around all 4 spark plugs, or just 1?

Jfrahm

It could be a leaking plug, if the plug is tight. Sometimes plugs leak a bit between the porcelain and steel. I'd replace the plugs and examine the one that is popping very carefully.

-Joel

Dave951M

Try replacing the plugs and wires first. Thoroughly clean the area of any trace of oil. Drive the car for a while and look for any symptoms of oil being blown in past the valve cover. Also, look at the condition of the plugs when you remove them. If the electrodes are very oily in the cylinders in question, then you might have a serious problem, but at this time, I'm still thinking the valve cover has a leak, pressurizing the plug boot and blowing it off. It can do that because of crankcase ventilation. Which brings me to another idea, is there any form of PCV on the 968? Could the 968 version of the PCV valve have failed and the crankcase venting past any "weak" spot?

NeedPorscheSpeed

I just wanted to take this opportunity to thank all of you for taking time to respond to my request for help. I hope to delve into the 968 this weekend, and your advice will prove invaluable, I'm sure. Thanks again to everyone!

my87944s

HEY, I didnt even think about a possible loose plug!!! CHECK THAT FIRST! It would be a real PITA to take the valve cover off, need to replace the gasket and all the seals JUST TO FIND OUT the plug was llose and allowing oil up there!!!
If the plug seems tight, take it out anyway and look at the threads... its POSSIBLE but unlikely that there could be damage on the threads alowwing oil up.
Good luck, and if you need any help with the process of removing the valve cover, and replacing the seals, let me know... I just did this on Tuesday!

Rob_in_NorCal

Hi,

I just bought a well-sorted 1990 944 S2, and after a week and 230 miles of care-free driving, I had this same thing happen to me.

After two hours of driving, then sitting off for literally two minutes, the spark plug boot of cylinder 2 popped off during engine startup (I could hear it clank the hood), and after talking to the mechanic that did the PPI on the car, he suggested I push it back on and drive over to his shop for a look. While there, the boot popped off twice more, only during startup. A torque wrench confirmed the spark plug was properly tightened and I assumed seated, and a flashlight showed only a little bit of oil around the base of the spark plug, which the mechanic thought was normal seepage. Inspecting the boot itself, the mechanic seemed to think that it was a bit loose mechanically, in terms of snapping onto a spark plug, and suggested replacing it with a new one. The previous owner suggested the same.

My question, however, is what would cause a pressure buildup there besides some leaking from the valve cover chamber, which is what led me to find this thread. So - even though this thread is 9 years old - did replacing the gasket ring that seals the spark plug chamber fix the problem? Any insights appreciated.

thanks,
Rob

ChrisRL

Yes, another soon-to-be 90 944S2 owner also wants to know what happened! :-)

Rob_in_NorCal

More searching has yielded a possible explanation for this "popping" phenomenon:

"40 years ago I used to see this on 1600 hemi Corollas. They didnt have any drain port for the plug tubes. When they started to leak a little oil around the round seal in the center of the valve cover, and the car was running very high load (which pushes secondary voltge high), they would arc between the plug wire cap and the tube wall. If the vaporized oil-to-air ratio was right, they would fire in the plug tube and pop the wire right out of the hole. This problem is more easily induced if you are running lean, because firing voltage goes much higher on a lean cylinder (clean, dry, highly compressed air is a great insulator.)"

http://cx500forum.com/forum/technica...pping-off.html

Anyone have this problem, and solved it?

mytrplseven

+1 on replacing the plugs. Cheap, fast and certain.

Rob_in_NorCal

Thanks mytrplseven!