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Discussion Starter · #1 ·
During the colder days (for 280ZX owners) do you notice that the idle sets itself quite a bit higher than normal?

When starting cold, the car would idle at 1500-2000RPMs, clutch in, or whatever. Now that it's gotten colder, it's a consistant thing. The engine also runs at that speed when it's in gear too, and doesn't back off when the gas pedal is left alone. It'll drive at 2200 the whole time. I thought that in motion, letting a car go without gas it would slow itself down. What I'm wondering is that is this a common occurance for 280ZX's (mine is a 1979 model year if that makes a difference) or is this something that I should worry about and go have fixed?
 

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Discussion Starter · #4 ·
No..

Once it gets to regular operational temp, the "Water" light on the comp goes off (turns off, it stays until warmed up) Usually it does, but it's not consistant. I've only driven newer cars, and I have no ideas about older engines. I admit to enjoying paying someone else to sort out my problems.

What does the cold start valve do? The idle usually goes down to 1000 (which is 250RPMs above, but I can handle that) however, the cruising without my pedal or permission still happens. It has caused some trouble before.
 

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Re: No..

a cold start valve lets more air into the engine causing greater rpms in order to heat the engine for cold weather running. However this should turn off as soon as the engine reaches normal operating temp. SO i'm asking if the RPMS drop during idle once it reaches normal operating temp.

One thing you def. wanna do with an older car in the morning is go outside and start it up like 5 minutes before you leave, this gives the engine a chance to get goin. Then before you start goin, tap the gas pedal a few times, just to get the juices flowin. If this doesn't solve your problem take it to your local Mech, or check the FSM.


a lil more info would be nice also, like as to what year ( maybe you put it and i over looked it, but everything helps, 5 spd? 4? auto? thanks )
 

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The air regulator has a "door" that is suppose to close once the engine warms up. It is really easy to test. Remove the air regulator from the car and put it in the freezer for 20 minutes. Take it out of the freezer and see if the "door" is open. If it is, then re-install the part back on the car. Letting the engine get to normal operating temp. Shut the car off, and remove the hoses to the regulator and see if the door is open or closed. If it is open, then you need to replace the part. If it is closed, then the regulator is functioning correctly.
 

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Wrong terminology...

"jetblack" has the right idea, but wrong term. It's not the cold start valve (which is the extra fuel injector behind the throttle; it's the "air regulator." This is a valve that sits next to the cold start valve and allows more air into the engine when it's cold; it's kinda like a choke. As your engine warms up, this valve (which you'll notice has an electrical connector) receives an electrical signal that heats up a metal strip inside. As the strip heats up, it closes a shutter that prohibits extra air from getting to your engine, since a warm engine no longer needs the extra enrichment. If this valve fails open, it allows air to bypass the throttle all the time, hence higher idle. Warm up your engine fully. Remove the hoses going to and from the regulator, and the two bolts that hold it in place (no need to unplug the connector). Pull the regulator from the hoses, look inside it, and you shouldn't be able to look through it. If you can, it's failed open.
One other possibility is your BCDD (boost controlled decceleration device). It sits underneath the throttle. It has a rubber plug cover at the far bottom, which you can remove. Inside is a little shaft with a slot in it, which you can turn to adjust the BCDD's calibration. The BCDD can also fail sometimes, or get out of adjustment, resulting in a high idle. Turn it clockwise to lower the idle. I had a similar problem to what you describe: as I deccelerated and put the clutch in, the idle would hang up at 2000rpm. Problem gone after a BCDD adjustment. If you tinker with this, use a mirror to note the original position of the shaft in case it doesn't help!!!!
 
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