My 88 3.2 Carrera hunted when cold until I installed a Steve Wong chip. You might open the DME and check the fuel optimisation switch. It probably should be set to 0.

http://forums.pelicanparts.com/porsche-911-technical-forum/825875-1987-3-2-carrera-motronic-dme-questions-optimisation.html

Yes but if was running well before then it could not be the switch. Something else made it idle wrong.

Original factory chip in the DME? Oil fill cap snug?

I just opened up my DME box to check the chip, here are the info I found :

DME part # 911.618.111.19
Chip part # 1267355357

I googled the chip number and it seems it relates to the US spec 3.2, mine is a euro 3.2 (930/20), could that be my problem? whats the correct chip for my engine?

Tighten down those intake runner bolts!!!!

Looks like you have the right chip for a late ROW 3.2 Carrera. At one point, my shop retorqued the the intake bolts and my engine sounded and ran better. It must have been leaking some.

Bottom line for both my 87 and 89 Carreras was that the initial surging on cold start before the car warms up was dirty (tired) ICVs.

On the 89 (112k miles), which was the car suffering the most, after cleaning once with carb cleaner and a little WD40 the car started without any surging. The second time it surged a few times then evened out. I decided to clean it again and also manually actuate it, in both directions, by applying voltage with alligator clips. In one direction the ICV is not quite as smooth as in the other direction (open/close). I am going to assume that the motor/contacts are getting tired. I will order a new ICV.

On the 87 (134k miles) the car only surges a couple of times before running smooth so cleaning worked pretty well. I must also say ICV on this car is in better physical shape, both cosmetically and operationally. I must conclude that this valve was replaced before I bought the car some 8 years ago.

I hope this helps someone here. I love these forums! Thanks for your help guys.

For the hunting idle at cold start, try backing the idle bypass out a half a turn, before you start it cold, for the next few starts. It should improve a bit. If it does, keep going. I think the loop tuning in the ECU is a bit basic and goes into oscillation if it's asked to do too much.

If it makes it worse, go the other way. When it's warm it will idle the same (as others have noted).

Usually backing the bypass out makes it worse and in was the cure for mine.

Cheers,

Joe
87 Carrera

UPDATE : I went a head and ordered a Steve Wong chip and got it installed, surging and hunting went away and it idles smooth and nice, problem solved!

I use Liqui Moly 10w60.

Cheers,
Harry

My 3.2 started doing the same thing (hunting idle on cold start), a couple of years back, but settles down to a even idle in 30 seconds or less, and isn't getting worse, so I don't worry about it. I expect there is a minor vacuum leak somewhere. Otherwise runs very well.

Glad you found a work around. However, Wear on the AFM tract as well as dirty idle contact switch can cause this problem as well. Check the AFM wiper if you have any low-speed hesitations.