86.5 928 stalls at 2000 rpm one time after starting. Idle, while smooth, slowly increases from 650 to around 1100


Asked by Mar 31, 2016 at 10:20 PM about the 1986 Porsche 928 S Hatchback

Question type: Maintenance & Repair

my 86.5 has an S4 intake installed by the PO that I recently refurbished (see
pic). Also upgraded injectors to Bosch Gen III 4 hole. Also purchased and
installed a refurbished MAF (JD Porsche).  Smoke tested it and seemed fine.
Runs spectacularly except for the initial stall at 2000 rpm and the slow
inexorable increase in idle speed. Idle is also very smooth -- just fast...

3 Answers


Got you all stumped too, apparently... Bummer...


Well in the pic it looks like a vacume hose is hanging over the valve cover. But my first thoughts would be IAC idle air control. Had similar symtoms with a first gen miata. Im not familiar with 928 as much as i would like to be, so maybe check the 928 forums and see if someone else has had the same issues. Good luck.


Thanks for the response. The intake refurb was still in process when the pic was taken so stuff is still disconnected. My leaning is also toward the IAC but on a 928 it's under the intake - -NOT a trivial task!

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