Idle running @ 2000 to 2300 rpm after warmed up.

[Robert911]

When starting the car cold, it idles @ 1000 rpm for about 15 minutes to 20 minutes. After it warms up it idles at @ 2200. I replaced the O2 sensor but no luck. Any suggestions.

[Tim Walsh]

what induction system on what kind of car is it?

[Robert911]

1980 911 SC CIS

[TerryBPP]

vaccum leak most likely. thats what was wrong with mine, but i dont have O2 sensors either.

[fred cook]

Sounds like you might have a problem with your AAR (auxilary air regulator). It is locatec on the right (passenger) side of the engine. Look at the right end of the airbox cover and staight down. It will have an electrical plug and a large vacuum line attached. To remove it, you will need an allen wrench (don't remember what size) to remove the two bolts holding it to the engine and a screwdriver to remove the vacuum line. You might need a very small screwdriver to release the electrical plug.

Once off, put it in the freezer for about 10 minutes to make sure that it is opening completely when cold. Let it sit in a warm place for a few minutes to make certain that it is closing. Once closed, try to blow thru the vacuum line fitting to make sure it is not leaking. If it fails any of these tests, replace it. If everything is ok,
well you just spent about an hour learning about the care and feeding of the AAR but did not spend any hard earned dollars! Once the AAR is back on the car, check to make sure that you are getting 12 volts at the plug.

Good Luck!

Fred Cook
'80 911SC coupe

[Jdub]

To add to Fred's reply, if possible 12v should be run to the tab that operates the bimetallic strip that, when warm from 12v current, will snug up the AAR's opening and cause the unit to no longer permit air to pass through.

But truly these units do open and close a bit due to ambient temp. even as you drive. The effect though is one where, when cold, enough air passes through to raise the idle, but once warmed up by way of 1)12v and 2)ambient engine temp. the idle comes down to the prescribed 900 or so RPM.

By the way, the air passes through a hole in a larger round piece. That round piece is set to move by way of the bimetallic spring. When cold, the hole permits air to pass through the vaccum hose. When warm the bimetallic spring move the hole over, choking off the air flow through the hose. I believe that the hole never totally closes, and that there is usually a sliver of hole always permitting some air through. Comments?

John

[jason2guy]

robert, im going through the exact same thing. i am actually on my 3rd brand new AAR. the first 2 were faulty, believe it or not. i just got of the phone w/bosch.
go and get a new one and put it in, hopefully youll get a good one
good luck

[Jocke]

Maybe it isn´t just one problem, I had the same problem last summer and I found out that it was a leak on a vaccumline and no power to the AAR.

My vaccum leak was in the line that goes to the servo-brakes, not that easy to find because the line goes above the gearbox.

/J

[Vipergrün]

Have you tried disconnecting and plugging the vaccum line to the decel valve? Sits just behind the AAR.

I am chasing down some stuff as well. Cannot get my idle to drop low enough to check timing with vaccum lines disconnected
and idle screw all the way down

[Schuey]

I am having an idle problem also...looked through 101 projects, just got my bentley and couldn't find it in there, I'm gonna keep the faith and keep reading, but I saw this:

IDLE SCREW...where is this?

[Vipergrün]

Schuey, the idle adjustment for the CIS cars is the large (3/4") slotted-head screw on the left side of the throttle body back near where the throttle linkage is. Clockwise to decrease idle, counter-clockwise to increase.

[Schuey]

Thanks bb80sc...worked GREAT!