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2005 CTS/ 2008 DTS/ 2008 STS V8 N*/ 2011 CTS4 ALL W/D Pearl
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Discussion Starter #1
If someone could start their car cold after sitting 4-8 hours I would like to know how the RPM's react.

My DTS always starts at 1100 drops to 900 after 10-15 seconds then goes to normal 650 after about 10-20 seconds. Total = about 20-35 seconds.

I thought the CTS always took a little longer but I think it might have become even a little longer lately?

The CTS starts at 1100 drops to about 900 after 15-25 seconds then goes to normal 650-700 after about 20-30 seconds total= 30-55 seconds, does that sound normal to you guys?

I know I know a lot of you just start you're cars and go but I never have for reasons. So if any of you are like me and wait for it to drop to normal idle please respond and if you think the time laps of the CTS is off please let me know why you think that could be. Thanks.
Both cars run great.
 

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06 CTS Sport/Luxury package
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What is you outside temp when you start it? It'll be a little off if your findings are done when it's 80*F for you but for me it would be 20*F. So those times would be a little longer for me.

KOT
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Different cars, different engines, different ambient temps, different idle sequences. And they also vary with coolant temp and time since last shutdown.

Just like the different idle cam timing for the exhaust stove heated choke pulloff spring in your old '65 Chevy and the electricaly heated choke pulloff in your '73 Oldsmobile. Different temps = different fast idle and mixture enrichment times.
 

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Discussion Starter #4
What is you outside temp when you start it? It'll be a little off if your findings are done when it's 80*F for you but for me it would be 20*F. So those times would be a little longer for me.

KOT
In the winter it might take 4-8 seconds longer but not a great deal after sitting over night. I'm just curious if it takes the same time for you guys because I very seldom drive the CTS and just thought it might be taking a little longer than I remember, it is warm out now.

I totally understand what Sub is saying I was just hoping someone would jump in their car and take 1 minute to see if the idles match that's all.

I'm pretty sure my DTS idles about the same as Sub STS so just wondering the time frame on someone's CTS?
 

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Discussion Starter #5
I was thinking maybe it had something to do with open and closed loop and an O2 sensor might be getting lazy?
 

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06 CTS
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My 06 3.6L drops to around 700 after 1-2 minutes. If I try to take off before letting it settle it will jump and thud into to gear. I always let it sit until the rpms go down. It doesnt matter if it is 110 or -30 degrees out. Never owned a car that was like this one.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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I was thinking maybe it had something to do with open and closed loop and an O2 sensor might be getting lazy?
The fast idle sequence has nothing to do with loop changeover. For the Northstar, loop change occurs at between 140 - 160 degrees coolant temperature - and that loop change depends on ambient temperature as well as sensed rate of coolant warmup. I daresay that, in most modern electronically controlled engines, the emissions changes are controlled about the same way........... remember: during a cold start the fuel mixture is enriched (the "choke") way outside the O2 sensor ranges - until the enrichment stops and loop change occurs you would get all sorts of crazy readings.

If you want to watch loop change (takes a hawkeye) - get either an UltraGauge or ScanGauge-II (Google each), plug it into the diagnostics port and set one of the observed gauges to "loop". During a normal startup-drive you can see when, and under what engine conditions, loop change occurs.
 
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