krahmlow

Has anyone had/seen this problem? I've only had this car for a short time, so I don't know it very well, and I'm trying to fix a misfire. The old dist. cap was cracked inside. When tightening down the new new one, I heard it crack, too. I ran my hand around the plate where the cap sits and found a definte bump (I also found a few more, but they're not so noticeable). The dist. cap has three cutaway areas along the area where it seats, but they don't seem to match up to the bump. I've attached a pic., in case you're wondering what the heck I'm talking about.

What is this? How should I go about fixing it? I thought I had it aligned correctly. My initial reaction is to pull off that plate and look to see what's causing the problem, but I can't find an exploded diagram of that part of the engine in the shop manual. I don't want to make more work for myself than I have to. I could just tap the metal flat or try to grind it flat, or I could shave down that area of the new cap, but I'm wondering if there's a problem inside that needs to be checked out. Any ideas?

Oh, the car is an '87 944S.

Zero10

Shouldn't there be a gasket or something in there?
On the 8v's there is a foam gasket between the distributor cap and the housing.
If there is supposed to be a gasket, then I wouldn't worry about a bump. Otherwise that is not right...

PorscheDoc

Zero10 is right there should be a gasket sitting there. Also if the cap fits snug i wouldnt worry about it.

krahmlow

Thanks, guys. I'll see if I can track down a gasket. There wasn't one on there, which I suppose is why the dist. cap was cracked in the first place.

aribop

16 valve engines do not have a gasket there like the 8 valve. The cap fits flush on top of the gear cover. The magnesium castings of the gear covers are pretty bad. You might try filing down the raised area and not tightening the cap so much.

Zero10

Really? No gasket?...
Perhaps you could use some thin foam tape to even it out a little. Seems like a gasket would be a good idea. That is, if you can't get it flat by filing, or if you don't wish to file it.
Heh, that's why I said I wasn't sure if there should be one.

krahmlow

Well, I figured I'd post a follow-up in case anyone sees this bizarre problem again. It looks like aribop is right. No gasket. I decided to pull the cap mounting plate/cover thing off to see what the problem was. Not a difficult job, but you've got to pull off the air filter assembly and the plastic cover just below the metal plate to get the metal part off. When I got to look at the back side of the plate, it got more weird. Nothing was pushing through; there ISN'T anything pushing against it from the back side. It looked like the plate just started "bubbling" up in spots where it had small reinforcing struts on the back side. Maybe from vibration, stress, who knows. Anyway, I tapped the raised areas back down with a flat brass drift until the new cap seated securely without rocking. Reassembled. 3 hours to replace a distributor cap.

Runs better. Still got a misfire, though, so now I guess I'll replace the fuel filter and check the injectors.