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My dad has a 87 300zx na. When he starts it in the morning (cold engine)
the car will idle at 1200 rpm for about 5 mintues. Tune was done about 30,000 miles ago. I could not figure it out. Check engine light came on a couple of times but it was just a problem with the fuel temp sensor. The car has been doing the idle thing for some time now. thanks for any help.
86 z31 with 253,000 miles
75 S30
 

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I don't see why it shouldn't have a fast idle when it is cold. That is the job of the air regulator. If it stayed at 1200rpm when it was warm then I would be worried.
The air regulator is a simple bimetal controlled air valve, heated by coolant and an electric heater circuit. I suppose the shutter in the air regulator may be getting a bit sticky with deposits from an old engine. At least yours is actually working.
 

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My car idles at 900 rpm when my air is off.. then when i turn it on it jumps to about 1200 rpm. Don't really see a problem right now but could have problems in the future?
 

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If it's doing 1200rpm and has an auto tranny then that would only make extra heat in the tranny.
I would expect somewhere around a 100-150rpm rise with the aircon running.
 

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Stu, by "air regulator" do you mean the IAC? Excuse my lack of knowledge, but I'm having a similar problem.
 

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The air regulator is separate to the idle-up solenoid, FICD and/or AAC valve.
The FSM explains the function of each of the above parts in detail.
The air regulator is designed to raise idle speed on a cold/cool engine.
 

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Thanks, I just checked the FSM and ID'd the item. I will try to clean out my existing one, and/or order a new one if necessary. Appreciate the help, and especially the lack of ridicule.

MaxQ
 

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don't feel bad, my idle is always 1400 rpm

no matter how far I adjust my idle. The rpms will drop when adjusting it, but after a couple days it will go back to about 1400rmp. I just adjusted my idle 3 days ago to 1000 rpm, and its already at 1200. I have aftermarket cams, so it does not really like anything below 1000 rpm. I have no AC, no power steering, and I keep the ficd unpluged. I don't worry about my problem at all.
 
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