Pull the intake and i wager you'll find cracked hoses causing vacume leaks......the 'valley' is like a hothouse and things have been cooking for more than 20 years.

 

Murray
Here is the link for Dwayne's write up.

 

Sorry, did not paste it before sending....
http://dwaynesgarage.norcal928.org/1...%20Refresh.htm

 

Guys,
I've already got a pressure tester built......and a spare MAF around here somewhere - fresh rebuild.
I'm making another run soon down to KW to yet once again charge the AC.....*^%$"high side "O" ring blew after I got home last Saturday....long story....I'm an idiot is the Reader's Digest Condensed Version of the ending though. Sorry for the "spoiler".

 

Anyone know for sure if the '89 and '90 MAF units are interchangeable?

 

Yes, they are.

 

All MAF' s from LH equipped 928's are interchangeable ('85-95 and '84 euro S2).

 

And Sean to the rescue again...

Thanks!

 

And Hilton..

 

So, when are we having the BBQ at Murray's place?......and where's Imre?

 

Ok I disconnected the battery again to reset the brains and disconnected the o2 sensor.
The extreme surging stopped. I reconnected the o2 sensor and it continued to run without surging. The idle is still low and it stumbled when coming of the throttle. Under the hood I can hear a loud air hiss after I blip the throttle. The hiss is there at idle but is dramatically louder just after the throttle closes. The loud hiss lasts about a second and sounds like it is from under the intake near the back.

Could it be the vacuum hoses going under the intake as suggested or perhaps a loose MAF boot or is that sound "normal"?

 

Could be a loose MAF or a split hose on the ISV. Only way to know is to isolate the MAF and if that's not it, then it's time to pull the intake.

 

There is a normal suction sound from the intake, but there's no loud "hissing" sounds....

 

Had a similar problem on mine, idle surging, stalling... My friend Dean from here cleaned the maf and we installed new o-ring and upper gasket on the maf, although this was many of the things I did in my search, including new plugs and wire from Roger, and finding one coil ungrounded, also new caps and rotors, but it is fine now. You could hear the vacuum leak from the maf at 20 ft. Hope this helps.