Flying Sparkplug Confession

huff923 · 12-02-2008, 07:00 AM

My 1988 3.2 is now driven under 1,000 miles per year and has less than 3,000 miles since the 60,000 mile major tuneup done by an independent Porsche specialist. It burns maybe a quart per 800 miles, which seems ok. Hand movement of the valves indicates the valve guides are not overly worn.

So I was driving to the airport to take a flight I could not delay due to family commitments at the other end, and I suddenly lose power and hear a chuffing sound and smell gas. I stop and take a look, and the left rear spark plug boot/connector is off and hanging outside the shroud. No sign of the spark plug, but its clearly gone somewhere.

Now I know what you do at this point is to stop and call a flatbed. But, I could not afford to miss my flight, there was no sound like a busted off valve head crashing around in there or a rod loose. It started and ran, so I made a tough decision and kept driving another 40 minutes to the airport. The car is now in storage and I won't back to it for several months. I just retired (things like this happen shortly after you retire) so I have time to get Wayne's book and rebuild it the slow, frustrating, educational way, with help and inspiration from yoozall.

So what do you guys think happened in there, and what am I likely to face? Its ok if you want to call me stupid for driving on. I have mentally prepared myself.

cgarr · cgarr's Garage

So the spark plug fell out and you drove it without a spark plug in one cylinder? That's it? The only other thing I would have done would be to unhook the injector to that cylinder and drive it home.

huff923 · 12-02-2008, 08:00 AM

Thanks for the reply, cgarr.

Murphy tells me that best case the engine comes out and that head goes for a rebuild. So maybe some gas washing the cylinder wall might have affected the rings? I dunno, seems like some amount of oil from the crankcase should have gotten to the rings.

Don't tell me someone got away with just replacing the sparkplug? Sounds too good to be true.

jpnovak · 12-02-2008, 08:30 AM

I would try to screw in a new spark plug. If the threads hold then plug the wire back in and drive it. I would not rebuild unless absolutely necessary. A few miles of gas on the cylinder will induce a small amount of wear but I would imagine this would be negligible.

cgarr · cgarr's Garage

I would just put a plug in it, watch the threads in the head they may be a bit messed up at the top, I would guess the plug was never tight, should check the others too. If the plug goes in ok, hook it up and run it. Its really not much different than running around with a fouled out plug which I have done before.

88911coupe · 12-02-2008, 09:28 AM

There was a thread some time ago about spark plugs mysteriously coming out but I don't recall the resolution or explanation. I second the idea of being careful to not bugger up the uppermost threads in the head since they may have some damage as the plug was just coming lose. There are thread cleaners that you insert into the hole and then they expand out and you then back them out which may be an option here. You can probably find a mechanic there to do this. Where in Oklahoma are you? Rennsport in Tulsa is very good and Tom Charlesworth (Tulsa also) is one of the Panorama's tech guys, although I've never used his shop since I hear he's more of an expert on 944's and 968's.

huff923 · 12-02-2008, 09:33 AM

Thanks to Craig and Jamie, this is good advice which I will follow.

huff923 · 12-02-2008, 10:05 AM

Hi Buck,

Thanks for the good suggestion. What you guys are saying is good news. I know Tom Charlesworth is a PCA advisor and a good guy, but the car is in storage in Keller, TX. Tom's shop did not do the 60,000 major.

Sounds like Murphy would be glad to help me crossthread a new plug in there. Al Zim's shop in Bedford is not far away, maybe I could flatbed it over there (Hagerty insurance) and they could chase the threads and advise before I either drive back or trailer it back to my shop.

I live in southeast OK about equidistant from OKC, Tulsa and Dallas. Official Porsche-free zone. I bought this car in Austin in 1997, a shop called Pro-Technic did the PPI.

Steve

jcge · 12-02-2008, 12:53 PM

Maybe take a look down the plug hole with a bore scope to check out the valve heads and cylinder wall

88911coupe · 12-02-2008, 01:17 PM

Zims is a good shop and I've had a few things done there over the years that I did not want to handle myself. Crossthreading that hole opens up a whole new can of worms!

Not near Broken Bow are you?
Good Luck

304065 · 12-02-2008, 01:59 PM

Put a new plug back in, use the tool in the tool kit. Put the wire back on. Drive away.

I would be shocked if the plug threads pulled out, I don't think the modern heads use a helicoil (OK, "modern" to me is anything newer than 1968). The plug probably was loose and backed out under millions of compression cycles.

kenikh · 12-02-2008, 03:19 PM

Even if the top threads are knackered, look up the "thread chaser" thread on this forum. The likliehood that all of the threads stripped our are zero to none. I think you got really, really lucky!

robmog · 12-02-2008, 03:54 PM

i want to know where the plug went.
wouldn't the engine tray hold it?

porschenut · 12-02-2008, 06:05 PM

It's gotta be in there somewhere.

It must have popped like a champagne cork when it finally let go.

850dunstall · 12-03-2008, 05:16 AM

i was riding in a 68 beetle being driven by a relative and the same thing happened, the plug just backed itself out. i screwed it back in with my fingers (yes it was a little hot) and kept on driving to be torqued at the end of the ride... no sweat. there need not be any damage

huff923 · 12-03-2008, 07:12 AM

Thanks to all for the good advice, which I will follow when I get back. I don't know where the plug went but it went somewhere not readily visible, I am not where the car is to be able to look in there.

I ran a search on "sparkplug threads" on this site and up came a thread by a racer who had a couple of plugs back out, with no major damage.

I will report back when the mystery is solved.

Schwarzeritter · 12-07-2008, 09:57 AM

I would seriously find that plug and like put it on a key chain!
That is crazy, although I have seen a few things like this, well I supose this makes
you the first guy to have currently a flat five " yes yes I know poor form-poor form "

Well I would just try and stick a plug in and see if things work.
As another gentelmen stated you could of washed the cylinder but then again there
should of been just enough oil to get you buy. I highly dbout you trashed on it either.

But if it makes you feel one bit better, once I was told that a BMW poped a plug and on a test drive and after a servicing and apparently it poped a injector. As to what caused the injector to pop is another story but the thing when up like a christmas tree!

I would also inspect the threds, a mirror + flash light will be required.
I would change the oil too.

Rot 911 · 12-08-2008, 05:44 AM

I bet the spark plug didn't get properly torqued when you had the 60K mile tune up done. Just took 3000 miles to work it out. Like the rest said, just get a new plug, screw it in properly, and drive.

huff923 · 12-14-2008, 03:29 AM

Kurt V,

Thanks for confirming the lack of torque on that plug. I will take your advice. In retrospect, its amazing I did not set the car on fire. Would a smear of anti-seize on the plug threads be advisable, or could that be part of the original problem?

Hey, I'm only 10,898 posts behind you!

Rod Schneider · 12-14-2008, 11:29 AM

It's also possible the plug broke and blew the center portion out. I saw that happen once on a VW Rabbit. The plug broke right where the threads ended at the base under the sealing washer. Fortunately, I was able to extract the threaded portion (the hex blew off and disappeared with the rest of the plug) with a large screwdriver. Put a new plug in, and all was well.