High Idle (1800-1900)on start up but 950 w/in a few min.

[boyt911sc]

Originally Posted by cwinters01

Wow, interesting. Over the years I have had more than a few very reputable porsche shops work on my car in So Cal, and they never mentioned a high idle (1500+) at startup as being abnormal. Go figure... Thanks for the great information!
cw

Don't believe everything you read in the Internet. A good working CIS engine will experience high cold idle of 1500 rpm or higher even if you live in AZ unless the ambient temperature is in the 110 deg. F. Temperature 50 deg. and below will produce high idle because of the control fuel pressure. If you have a good working AAR, you can not prevent this cold idle during a cold start unless you are in Death Valley in the summertime. The CSV operates when the engine is below 113 deg. F (cold state).

Tony

[betterair]

Tony,
How have you been? Since you and I are in cold and wet Penciltucky, we don't have the luxury of the warmer climates that they have in the desert. But we sure do have better twisties.

Your Comment about the control fuel pressure impacting or producing a hide high idle caught my attention.
While I have not yet checked my CIS value since the rebuild, prior to that, My cold control pressure was 2.0 bar. Checking it warm after 3 min(with vac) =3.3 and 2.9 w/o vac.
Wur p/n 043363 826 mfgd 08/78.
Based on this, I am inclined to take masons and Johns lead and make the AAR adjustment ,which seems very logical.
What do you think ?
Bruce

[pampadori]

Bob, funny you mention the idle adjustment screw. Car is apart now awaiting an EFI and ITB swap but when the CIS was on her the idle screw would be completely in at the end of its adjustment just to get it down to 900rpm warm. Clearly had a few air leaks. The two I found when taking the CIS off were the crack in the box and an injector holder that was cracked.
Over the last 10 months it got worse and worse. The off throttle lean popping in the exhaust go so bad just before I took the CIS off that I was embarrassed to drive the car around much. Pop, pop, pop....look its a CIS 911 that runs like ****. Point and stare kids!
LOL


I don't understand how an air leak won't cause a high idle though. Isn't that exactly what the AAR is doing? Providing air to go around the throttle butterfly which increases revs?

[boyt911sc]

Originally Posted by betterair

Tony,
How have you been? Since you and I are in cold and wet Penciltucky, we don't have the luxury of the warmer climates that they have in the desert. But we sure do have better twisties.

Your Comment about the control fuel pressure impacting or producing a hide high idle caught my attention.
While I have not yet checked my CIS value since the rebuild, prior to that, My cold control pressure was 2.0 bar. Checking it warm after 3 min(with vac) =3.3 and 2.9 w/o vac.
Wur p/n 043363 826 mfgd 08/78.
Based on this, I am inclined to take masons and Johns lead and make the AAR adjustment ,which seems very logical.
What do you think ?
Bruce

Bruce,

Could you post a picture of the WUR you have. I am not familiar with that identification number. The Bosch ID # is 0-438-140-xxx. The last 3 digits identify a particular WUR? What is the resistance value (Ohms)? With regard to AAR, test it using 12-volts power and record the time it takes to close. Again, post the number and heater resistance of the AAR.

Unless you are very familiar how this CIS works, you can not just put any component and expect the engine to run as it should be unless you are very lucky. You can not rely on luck all the time. Knowledge and understanding how the system works is your friend.

Tony