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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,262
"Is there something else which could cause the revs to be really low until the engine is hot then idle fine (about 900rpm)"

Yes, if the throttle bypass valve #4 in your diagram is not opening when the motor is cold then your idle will be real slow like you say.
Take the hose off the inlet side and look in to see if the slide valve is open or closed when cold. There is a slot in the valve too.
The valve is opened or closed by a bi-metallic spring. There is a heating element to gradually heat up the spring and open the valve slowly when the fuel pumps are running.
It may just need a little WD40 sprayed in there to free it up or it may be shot.

There is a valve made that is manually controlled that you could put in place there for testing. You can also hook up a long generic choke cable to it so you can operate it manually from the inside of the car.
I've done that on L-jetronic BMW's because the cold start throttle body air bypass really makes the old L-jetronic big 6 cylinder BMW's rev annoyingly high when cold and for way too long.
It is the black plastic heater valve for a water cooled 944 or BMW 320i.
It has the same size hose connections as the aux air valve or throttle bypass valve on CIS. Installed correctly it will work perfectly for this if you want to do that.

Even cheaper and made of metal, is to put a ball valve there with the correct size hose fittings screwed into it. You can make one of those up for about $5-$8 at harbor freight tools.
Some crazy ideas, but they do work...
Old 11-10-2008, 09:13 AM
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