High Idle When Starting, Cold Temperatures - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 01-03-2008, 11:10 AM   #11
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Default Idle Problem

My idle goes down after I put it into gear and drive for 10 seconds. The idle returns to normal in and out of gear. It starts out at 1500 and ramps up to 3000. I'm going to try replacing the IAC control and the MAP sensor. I'll have to run the codes, something has to be out of sync. I don't think I have a vacuum leak, I'm just concerned because 3000 RPM when it'* 2 degrees outside isn't a good idea. This ONLY happens first thing in the morning. The car can sit all day and it starts just fine.
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Old 01-03-2008, 11:16 AM   #12
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That sort of sounds like the Intake Air Temperature Sensor...?

http://www.alldatadiy.com/alldata/AF...67128/34857046
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Old 01-03-2008, 11:19 AM   #13
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Default 1500 IS NORMAL

1500 on cold start-up is normal, especially if it is really cold out. Should cause no problems, and will drop down once the car gets even the slightest hint of warm. Only problem is that (in 1999'* at least) the PCM will command a pretty high tranny fluid pressure at this time ONLY when going into reverse, it will bang pretty good. It does not command this higher pressure when going into drive. There are 3 solutions to this - 1) let it idle for about 60 seconds, and when you tap the throttle it will drop down and then not engage reverse that hard. 2) Back the car into the garage so you don't have to wait, since it will not bang into drive. 3) there is a PCM reflash update that addresses cold start / driveaway reverse pressure setting, makes it not engage hard into reverse.
Actually, I suppose there is a 4th option, like my mother in law did FOREVER on her 1999, which by the way she sold with 240K on it and the original tranny, which is just start it, hammer it into reverse, and go... Literally NO warm up time AT ALL ever.. Mike
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Old 01-03-2008, 11:21 AM   #14
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I'll try replacing that sensor first. I didn't replace that one when I put the new motor in. Thanks for all the replies, it'* greatly appreciated. If it'* not Air Temperature Sensor, I'll go IAC, then MAP. Hopefully one of them will solve the problem.
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Old 01-03-2008, 11:22 AM   #15
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Default Re: 1500 IS NORMAL

Quote:
Originally Posted by TROYPORT
1500 on cold start-up is normal, especially if it is really cold out. Should cause no problems, and will drop down once the car gets even the slightest hint of warm.
Yes, it is normal for the first 30 - 60 seconds. The point we're making is that it DOESN'T drop. Just stays pegged at 1500 indefinitely.
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Old 01-03-2008, 11:22 AM   #16
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Before you replace them, maybe is there a way to unplug it and see if it sets the PCM to default?

Maybe try unplugging them one at a time and start the car each time to see if any of those help.
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Old 01-03-2008, 11:33 AM   #17
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To reply to this post, I can not kick down the idle. It'll sit there at 3000 RPM (this is after it slowly ramps up from 1500 RPM) The only solution is to put it in drive and take off. At the very first light, the car is idling fine. I tried kicking it down, no luck.


1500 on cold start-up is normal, especially if it is really cold out. Should cause no problems, and will drop down once the car gets even the slightest hint of warm. Only problem is that (in 1999'* at least) the PCM will command a pretty high tranny fluid pressure at this time ONLY when going into reverse, it will bang pretty good. It does not command this higher pressure when going into drive. There are 3 solutions to this - 1) let it idle for about 60 seconds, and when you tap the throttle it will drop down and then not engage reverse that hard. 2) Back the car into the garage so you don't have to wait, since it will not bang into drive. 3) there is a PCM reflash update that addresses cold start / driveaway reverse pressure setting, makes it not engage hard into reverse.
Actually, I suppose there is a 4th option, like my mother in law did FOREVER on her 1999, which by the way she sold with 240K on it and the original tranny, which is just start it, hammer it into reverse, and go... Literally NO warm up time AT ALL ever.. Mike
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Old 01-03-2008, 12:19 PM   #18
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Default OKAY

Sorry, I missed that.. these threads can get confusing sometimes. Thanks. Mike
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Old 01-05-2008, 11:42 AM   #19
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Default

I read this thread and everyone says it will return to normal when warm, but I don't remember what normal is. Is 1000 rpm idle when warm correct? I have the high idle issue after a transmission re=build. I have it idling at 1000 rpm when warm, higher when cold. My tranny seems to clunk into gear even when warm. It is not as smooth shifting while driving either. Can the shop fix that? I have a 12 month warranty.
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Old 01-05-2008, 05:59 PM   #20
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Default High Idle Problem

It was the MAP sensor. It was idling at 1500 at start up. It started to gradually increase and ramp up to 3000 rpms. I shut off the car and unplugged one by one the sensors. Air Intake Temp first (nothing) Intake Air Sensor (nothing) MAF (nothing) Unplugged the MAP sensor, problem stopped. Bought a new sensor, hasn't happened again.
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