Idle Adj. Gas savings ?

[hiskid1973]

Has anyone changed their crazy idle? 2,000 then 1500 gets its way to 1200 then 800 after 5 minutes or more..Even when it's 50 out you have to sit and wait..My wife drives slow to work anyway..Seems if I could get it backed down she could drive out soone and get better mileage..Dealer says it's in spec so they won't touch it..Can regular garages change it..? Anybody have their idle reprogrammed? Is 1200 rpm's safe to shift into drive..Thanks for any help..God Bless You..K

[Jpilot32]

that hurt my eyes trying to read that....i don't really know what you are trying to ask

[jerryp58]

Originally Posted by hiskid1973

Has anyone changed their crazy idle? 2,000 then 1500 gets its way to 1200 then 800 after 5 minutes or more..Even when it's 50 out you have to sit and wait..My wife drives slow to work anyway..Seems if I could get it backed down she could drive out soone and get better mileage..Dealer says it's in spec so they won't touch it..Can regular garages change it..? Anybody have their idle reprogrammed? Is 1200 rpm's safe to shift into drive..Thanks for any help..God Bless You..K

My manual trans doesn't get to 2k, only about 1.2k and sits there for a while. It may start stepping down but I never give it the chance. I have about 1/4mi of 25MPH on the way out of my subdivision so I give the truck about 30sec of warm up (it will always want to warm up to its couple of hundred degree temp no matter how cold or warm outside -- it'll just be slower or quicker getting there) before I start out. I just take it real easy on it on my way out of the neighborhood (1500 RPM shift). If your wife takes it slow for a little while, I don't think she'll have any problems at all. I wouldn't even attempt, or let anyone else attempt, to change the stock behaivour.

[FitzIngarage]

I don't know the year of your rig, but it could be your idle air controller (IAC) going bad. These are usually hung near the throttle body and have coolant hoses running in and out, along with a wired connection. They sense engine temperature and use a stepper motor to run a pintile in and out of a small oriface to modulate idle air. As they get dirty or go bad, idle speeds will be zany.

They can be cleaned (use throttle body cleaner only!), but be careful not to flood other components. I removed the one in my car and cleaned it on the bench. New ones are like $200 to $300 I think.

Anyway, this may or may not be your problem. One way to check is to unplug the thing with the engine running. If the idle stabilizes at the RPM you unplugged it, you'll know it's the IAC. Good luck.

[OldMechanik]

The idle speeds are computer driven, since when are they adjustable?Modern engines don't need to be "warmed up" unless it way below freezing out. Older, carbureted engines used to need time for the engine to heat as there was no computer to change fuel mix for the engine's temperature. You used to have to wait for the choke to back off and the speed was stepped with an adjustable cam on the carb...but we've come a long way since then.Just fire it up and go, you're not going to save any gas sitting in the drive waiting for the engine to come up to full operating temp.

[jerryp58]

Originally Posted by OldMechanik

Modern engines don't need to be "warmed up" unless it way below freezing out.

I could be wrong (have been many times before), but I have to disagree with that statement. Engines are designed to run at ~200*; anything below that and they're going to try to warm themselves up (via a closed thermostat and a high idle). It used to be done with a choke (manual, mechanical, or electric), now it's done with the computer, but I think it's still done. My truck will idle high 1200 RPM (same thing a choke would make it do) until the engine warms up and then it idles at 700 RPM.

[OldMechanik]

Maybe I didn't make my point clear...sorry...what I mean is this, yes the engine will run at a high idle speed untill it warms up, then it will slow progressively to a normal curb idle speed. There is no adjustment to these speeds on todays electronic engines and, with the latest oil technology and recommended weights along with low friction internal parts designs, morning warm up really isn't necessary. This characteristic is normal. The computer gets its signal from the coolant temp sensor and intake air temperature (along with other basic input sensors) and makes a judgment for idle speed based on the input info and the manufacturers maping.

[jerryp58]

Originally Posted by OldMechanik

morning warm up really isn't necessary

I agree.

I believe there was a thread (haven't searched for it) on this forum that talked about letting the vehicle warm up via a high idle versus letting it warm up with a slow driving warm up period. Part of the rationale was that even if you let the engine warm up via the idle, you've done nothing for the rest of the drive train. Starting out slowly and giving the engine, trans, and diff(s) a chance to warm up together was thought to be a good thing. That's what I try to do, and hiskid1973, I think that would be a good method for your wife to use. Just my $0.02

[FitzIngarage]

I now have a better understanding hiskid1973. I was confused reading your post -- I thought your idle speed was moving around regardless of operating temperature, hence my IAC suggestion. Yep, OldMechanik's spot on -- there's no way to rework this, nor would the result be welcome.