JPS

The heat sink is the bit of metal the ignition module sits on. The module gets very hot. Surprisingly so. Like can't touch the bottom of it lest you burn yourself hot. Then it fries. So the heat sink / metal dissipates it. You put the dielectric paste between the two so that it more readily transfers all that heat to the sink/metal.

red64chevelle

I think the terminology is messing people up. You don’t use dielectric grease for the heat sink. You use conductive paste. That is what helps the heat being produced by the module be transferred to the heat sink (the metal it is bolted to).

TDW993

Yep, this is a common mistake. I made the same mistake recently until I knew better. I thought they were the same thing with different names but they are not.

motobri

Thanks for the replies.
Anyone have a source that has the Bosch ones in stock?
Pelican and others are out of stock.

TDW993

There are a few available on other sites but they want crazy money. I asked the question and there appears to be no ETA from PP.

Brando 993

Cupcar I took a whole month to figure out this exact problem on my 1995 993 C2. Had only 6 firing on one side of the ignition coil changed that to a new one and still not much of a difference. When we changed the ignition control switch it was like the car was alive again. Start up was very smooth, no bogging in between gears and on load. Car sits at good revs when the car is stopped. I imagine like you said this must be happening to a lot of 993s where the module is shutting down one distributor. As you said it ran "fine" but not nearly as well as now with the fix.

Thanks

Coleman

I blew a belt on my distributor at some point, and didn't really know what was up with the car, except that it felt lumpy off throttle.. I tested the distributor and found a belt broken.. I sent it off to Rothsport for a rebuild. After it was reinstalled, the car drove incredible.. I must've been driving around with the broken belt long enough for me to get used to it.. As above, I inspect every so often and also add a drop of oil to the felt lubricant pad on top... I had an extra ignition control module, but I sold it on eBay last year..

Cupcar

The 356 Porsche Carrera 4 cam street cars and all the twin plug racing cars I know of had individual circuit interrupt switches for upper and lower spark plug circuits to test the circuits just like an aircraft does for its twin plug system. Turning off a set of plugs at the coil, with a dedicated switch or a simple disconnection, at least tells which circuit is involved for starters, then it is a matter of figuring out if it is the coil, distributor, module or wiring fault. Maybe Porsche should have gone back to their roots with such a system for the 993 but I am not sure the normal owner would understand what it was for, etc.