Oscillating at idle
 

Hi all,
I'm still on the proses of alienation with the fast oscillation at start up, this is when cold and warm. But not every time. My car is an 85 911 3.2 with a SW chip. the chip has been in there for over 9 years with no problems. I had the 2 Speed Reference Sensor changed, and thats when it stated. They will only plug in one way; I believe. The engine runs as normal, but if I let it stand and cool down some it will start to rev up and down again until it sorts it self out. I've had the idle regulator out and all the innards run free, hoses are ok and sealed. The oil return hoses from the front of the motor to the oil tank need to be replaced. Electrical plugs seem ok. It dose sound like a motor bike and not a cool sound for a car like a Porsche.
Any help thanks Steve.

Have you made sure the micro switch on the throttle body is set correctly, installed the jumper in the test port by the electrical console, and adjusted the idle to 800 rpm when warm?

I had a similar problem. A mixture adjustment cured it.

My '86 which otherwise runs fine started to surge a little only at cold start-up this spring. Kind of odd as if the temp was below 50* no surge. Once car had ran a couple of minutes no surge. I wondered about the CHT sensor but it tested in spec. I ended up richening the idle mixture half a turn on the AFM. Surge went away. -J

Another think that can cause a surge is a serious vacuum leak in the intake gaskets. If you have an IR thermometer gun you can figure that one out by firing up the engine cold and then see if you have exhaust ports that don't heat up like the others.

Next time it starts oscillation, go to the engine, and while it is running, give the idle stabilization valve, I think you call it the idle regulator, a bop with a small hammer. If the idle smooths out, clean or replace the valve.

If that doesn't work, try turning down the idle speed.


Cheers,

Joe
82 Targa, 87 Carrera