#82557 - 09/27/05 04:56 PM
Kind of a newbie question
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Registered: 08/09/03
Posts: 3256
Loc: Oregon
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What exactly happens when you first start your car up?
When idling at first I notice the RPMs jump up to about 1200RPM and then after about 20 seconds the RPMs drop to around 1k.
Is that RPM and time dictated by the PCM? Is the sole purpose just to get the fluids circulating before you put it in gear?
I was just curious....
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#82558 - 09/27/05 05:56 PM
Re: Kind of a newbie question
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Registered: 05/23/03
Posts: 8078
Loc: Austin, TX
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Yes, I believe it is controlled by the PCM.
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Died 5/1/08, resurrected 5/15/08
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#82559 - 09/27/05 06:40 PM
Re: Kind of a newbie question
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Registered: 06/18/05
Posts: 94
Loc: Virginia
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It is controlled by the PCM to get the fluids flowing and warm up the vehicle, etc. In addition, I recommend always idling your car for at least 30 seconds before takeoff. You have to remember when you first start up there is no oil pressure, so letting it sit for a second before takeoff will allow that oil pressure to build, and therefore increase your engine life.
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#82560 - 09/27/05 07:28 PM
Re: Kind of a newbie question
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Registered: 08/09/03
Posts: 3256
Loc: Oregon
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Originally posted by Daniel:
It is controlled by the PCM to get the fluids flowing and warm up the vehicle, etc. In addition, I recommend always idling your car for at least 30 seconds before takeoff. You have to remember when you first start up there is no oil pressure, so letting it sit for a second before takeoff will allow that oil pressure to build, and therefore increase your engine life. I let it idle until I hear the RPMs drop. I just wasn't sure if anything else was going on inside the engine during this time.
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#82561 - 09/27/05 09:19 PM
Re: Kind of a newbie question
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Registered: 12/01/04
Posts: 483
Loc: Colorado Springs
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Same here, LET IT WARM UP , the season is changing.........
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#82562 - 09/27/05 11:34 PM
Re: Kind of a newbie question
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Registered: 11/17/04
Posts: 712
Loc: Kansas (Redneck Country)
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someone once told me that it also has something to do with the EGR valve warming up, once it reaches a certain temp, it goes down from like 1100 to 750 or so. in the winter time, it takes longer for my car to idle down, so it kinda makes sense to me. I think it was the EGR, but i may be mistaking it for a different one
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#82563 - 09/27/05 11:36 PM
Re: Kind of a newbie question
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Registered: 08/09/03
Posts: 3256
Loc: Oregon
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Thanks all. We have relatively warm winters here, and I keep my car in the garage. In fact, it's near my water heater and furnace so it stays pretty toasty year round. 
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#82565 - 09/28/05 07:23 AM
Re: Kind of a newbie question
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Registered: 03/26/03
Posts: 2481
Loc: Franklin, MA
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I heard somewhere that 90% of engine wear happens in the first 2 minutes.
It might have applied just to bikes because they rev so high, but thought I'd throw it out there. I always let my bike sit until it gets to about 160 degress, I'm not so patient with the truck.
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#82566 - 09/28/05 10:15 AM
Re: Kind of a newbie question
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Registered: 07/15/04
Posts: 3141
Loc: Chicago, IL
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Originally posted by HercMan:
The high idle then low idle is actually the "choke" to get the engine started and stabilized before it goes into low speed idle. Alot of you probably don't remember how to use a choke I do.... 
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