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914World.com _ 914World Garage _ Cold Start Idle seems too high..

Posted by: DougC Jan 17 2006, 04:56 PM

When I start my car on cold mornings (anytime really).. the Idle shoots up to like 1800rpm and sits there for a good while. This seems too high to me, any recommendations?

Doug C

Posted by: Root_Werks Jan 17 2006, 05:03 PM

I have run into this on lots of 911's that use CIS. It's the Cold start air bypass vavle thingy. The hole is too big on the reman and new units. I have used a plastic cap with a small hole punched in it. I think it was 3/16" that worked perfect. When cold, the bigest hole was the 3/16" hole in your plastic cap (Hose fit over that of course). It is almost too small for 3.0's, but perfect for 2.7's. Keeps the cold idle around 1100rpms, when it warms up, down to 900 or so.

I have seen some roll in, they leave the car, I start it the next morning and they idle around 2500!

Posted by: DougC Jan 17 2006, 05:26 PM

This is the item at the rear of the engine (in a 914) that sits up above the sender for the oil "idiot light"?

Doug C

Posted by: Root_Werks Jan 17 2006, 05:33 PM

If you were looking at the engine in a 911, it would be on the passenger side of the engine, just about the upper valve cover about centered (over the middle plug wire). So in a 914, Drivers side. It could have been slightly relocated for the install into a 914-6.

It has one 3/4" or so rubber hose going to it, one 3/4" hose going from it and one two wire electrical conection (Warm up the unit faster then engine heat will). It's just an air bypass thingy that lets more air in when the car is cold so it idles faster. Closes when it warms up.

Posted by: lapuwali Jan 17 2006, 05:35 PM

QUOTE (DougC @ Jan 17 2006, 03:26 PM)
This is the item at the rear of the engine (in a 914) that sits up above the sender for the oil "idiot light"?

Doug C

It's the item with two large-ish hoses on it, one leading to the airbox, the other to the throttle body or plenum below the throttle plate. It will have an electrical connection, too. Exactly what you're looks like depends on the exact model you have. Some look like a can, others look like a disc with tube (where the wires go). They usually do mount near the rear of the car (in a 914), but can be relocated anywhere. The electrical connection is for a heater to heat up the device quickly, so the fast idle doesn't stay fast for too long.

1800rpm is pretty typical of these, and as long as it doesn't stay there a really long time, I don't really see a problem. It should slow down within 20-30 seconds, if the wiring is hooked up and the heater isn't dead.

Posted by: ClayPerrine Jan 17 2006, 07:08 PM

Remember that hole that I plugged with in the intake tube? That was were one end of the auxuiluary air regulator hooks up. When I was there, you had it capped off. The other end hooks to the intake plenum below the throttle plate.

If the electrical stuff isn't hooked up, it's gonna take a long time to warm up, so it will idle fast for a long time.