Hot Idle RPM Change?

mxyplxApril 5, 2010

My (new to me last week) '03 Ranger 3.0L stick shift hot idles about 600 maybe 650 rpm, cold idle about 1000 (45ºF). I spose all correct settings because it was just smogged last week. No problem with that but I'd like it to hot idle just a bit faster maybe 800-900 rpm to suit my personal style. Other than that the stock settings suit me just fine. So I'd have it done, of course, but supposing a shop would do it what are the implications.

Can they change that w/o changing all the other various settings?

What else gets necessarily changed? affected?

Would the cold idle be that much higher? Or stay the same?

Would it cause the engine rpm to float excessively when shifting? It doesn't float when cold; or does the computer control that?

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This is the newest thing I have ever drove. I got it home, grabbed up a couple screw drivers with intent to up the idle, popped the hood, took one look and thought whoops! Hhhmmmm. No carburetor = better study on this. Sure enough, this formerly minor procedure is now a shop job. :-)

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kalining

Put the screw drivers back in box. Close the hood and step
away from the vehicle. That is something you DO NOT play with. Leave it alone.

    Bookmark   April 6, 2010 at 11:09AM
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mxyplx

I understand that. Maybe I should rephrase the question:

Can a qualified shop (with 4711 years of training and experience and a million dollars worth of equipment) increase the hot idle speed to 800-900 rpm w/o screwing up the entire system?

Or to put it another way -- is it possible?

    Bookmark   April 6, 2010 at 7:07PM
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john_g

The only way to really change the idle speed is to change the computer software and make the computer control the engine at a different speed from its base programming. This is something that is occasionally done by the manufacturer if they discover that a particular set of vehicles display an unpleasant operating condition. Some aftermarket companies re-write O.E. software with changes to idle speeds, and do things with injection pulse width calculations and spark timing maps to enhance vehicle performance.

However, "if it isn't broken, don't fix it". Any change you attempt to make might improve one thing, while it turns around and causes an issue somewhere else.

Now, could I change your base idle speed by turning the throttle stop screw? Sure, but the system will turn around and set a trouble code for an engine idle speed control error. Could I alter the vehicle software and make the car idle faster, in fact yes I can, but I also know why I should not do so. If the O.E. releases a re-flash (software update) and they address an idle speed issue, then and only then would you see this be changed.

    Bookmark   April 6, 2010 at 8:29PM
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mxyplx

Thankyou. I rather thot there might be extensive ramifications but wasn't sure how much. I was aware of the aftermarket re-write performance enhancing possibility. Didn't want that. Just the hot idle speed. I'll therefore live with it.

If something doesn't sit me I try to change it. If it can't be changed I live with it. Knowing why it can't be done helps because I do hate to give up with just a shrug.

    Bookmark   April 6, 2010 at 10:38PM
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jemdandy

I'm wondering why you want to raise the hot idle speed? The cold and hot idle speeds you reported seem ok to me. The 600 to 650 rpm speed is about right for a manual transmission. If you had an automatic, the engine controller may give a small boost to the Idle air control when the gear selector is moved from neutral or park to a gear. That happens on the three automatics we own. However, a boost is not needed for a manual transmission.

    Bookmark   April 7, 2010 at 12:15AM
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mxyplx

It's totally personal.

This PU is higher geared than anything I've ever drove. Hate to admit it but I've killed the engine at least 20 times. In traffic. With the big trucks, 36 years, and my old PU, 26 years, I just got off the clutch at near idle then got on the throttle. That's how its done. My feet know what to do.

With this rig at cold idle, 1000 rpm, I have no problem. The old PU idles about 875 rpm. Therefore, I reasoned, a higher hot idle would solve it. Hard to break the habits of a lifetime. But I will perserveer with vigor. :-)

Even my wife is sympathetic.

    Bookmark   April 7, 2010 at 10:46AM
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jemdandy

I see your point. You've been driving truck engines that had almost twice the torque at idle and likely a lower gear or maybe a higher ration in the differential. It'll take some getting used to, but I bet you'll be able to adapt. Maybe the clutch action is not as smooth as it could be - a little grabby?

    Bookmark   April 8, 2010 at 3:53AM
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