Did the spark plug pop out?
 

Driving home last night in my '88 3.2 targa and quite suddenly the engine turned from purring to a very loud popping and clanking. Excuse the description as I'm nearly deaf.
Limped home and was able to see the spark plug cable going to #6 had popped out. (magnacore as other threads have complained). After much effort I could not get a good seat on the spark plug or hear the click. I pulled the cable out to have another look and guess what was attached? Yup the plug. Head scratched, I screwed the plug back in, got a good seat with the cable and the purring has returned. The question is: can a spark plug come unscrewed or was it never in properly in the first place (I did a tune up last year)?

It was loose.

Perhaps not properly torqued.

Check the other plugs for the proper torqe. (22 fb-lb)

Gerry

I've cross-threaded a plug before, and it popped out. Ugh. Had to get it heli-coiled, but it worked.

P.S.----this was not a Porsche, but it's ugly distant cousin.

That used to happen to one particular cylinder in my beetle occasionally.