Cant get my newly swapped in 3.2 to idle.
 

I just finished swapping in a 3.2 into my 76, the engine came from a 85 RoW car so I think it doesnt use O2 because it came with a resonator instead of the cat. Everything was straight forward and smooth except when I finally started the car up it idles up and down for 5 seconds then it dies, unless I keep the idle at around 2000 rpm. I'm really familiar with the american V8 engines but totally new to the Motronic system. Where do I start looking for to figure it out?

Very possibly a vaccum leak. Borrow a smoke tester and give it a smoke test. You will have to remove the fan and as much of the air box as possible to see the leak.

You can also buy one cheap on eBay. Do the exhaust too.

sounds like it could be the IAC (idle air controller). Do a search on the forum, you'll finds lots of info on how to test and or clean it.

I believe your base idle setting is so far off, the IAC can't do the fine adjustment, so it's hunting. Have to take the IAC out of the loop by jumpering it once it's running, then use a meter (or tach if you don't have a meter) to set the rpms to 900. Once set, remove the jumper wires and the IAC should now work properly.
Search this forum on how to jumper the IAC to set the base idle. Is a socket in the left side of the engine compartment that needs to be jumpered.

The first thing to check is whether the little micro switch on the throttle body engages with the throttle all the way closed. That is telling the computer to go into idle mode.

If the linkage it a little tight it can prevent the throttle from closing all the way.

Ingo

You were correct, it was a vacuum leak caused by a slipped out vacuum hose from the fuel regulator on the back of the engine, got it connected and its now idling just fine, I will take it for the 1st test drive tomorrow and hopefully everything will be fine.

Thanks to all for all the valuable comments, definitely I learn a lot from you guys. Thanks again!

Now it idles OK, but I've noticed that when I hit the throttle it hunts up and down for a second and dies. as long as I keep it idling its fine (idles at about 1000 rpm) but it just hunts around and dies when I press the throttle. do I need to re-adjust the mixture and/or the idle speed to remedy this issue?

OK, found the main culprit : the previous owner of this engine had the IAC put upside down, once corrected the car ran and drove fine. Now I need to get the idle to come down quite a bit as it idles at 1200-1300 rpm and I got the idle set screw fully clockwise. I checked thoroughly for any vacuum leak and couldn't find any.

Did you check the switch that Ingo mentioned above?

An open idle switch can make it idle that high, although so could an improperly adjusted idle speed.

So if the switch works, try setting the baseline idle per rusnak's post #10 in this thread.
http://forums.pelicanparts.com/porsche-911-technical-forum/738755-idle-adjustment.html