High Idle Mod
Senior User
Joined: Mar 2010
Posts: 419
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From: Timmins, Ontario, Canada
I've done a high idle mod as well; put a switch on the dash that switches between normal/auto, off, and forced on. Basically wired a relay across the coolant temp switch so when it isnt energized the circuit is normal, but when i push the button the relay jumps the 12V right over the temp switch to set the fast idle and advance timing.
Also added a light to indicate when then coolant switch would be closed even if its off or overridden. Handy mods here where the engine gets cold so fast that the coolant at the switch is hot enough but the engine won't run at idle. I have schematics drawn for this, if they're wanted.
Also added a light to indicate when then coolant switch would be closed even if its off or overridden. Handy mods here where the engine gets cold so fast that the coolant at the switch is hot enough but the engine won't run at idle. I have schematics drawn for this, if they're wanted.
Postmaster
Joined: Apr 2008
Posts: 4,802
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That is correct, and you use a diode for this. I actually had it wired without the diode initially, must have been feeling lazy I guess, so when I flipped the switch both the fast idle and the cold advance solenoids got powered up. Results were quite interesting, to say the least - just idling in park in my driveway she'd revv up on her on to about 2500 rpms, then the governor would catch her and defuel, which results in a quick rpm drop to below normal idle speed (almost to a stall) where the governor would catch her again and add fuel and the rpms would shoot up again. Kinda like a runaway situation, but not quite. I never felt brave (or stupid) enough to try engaging the system with the truck in gear, instead I wired it properly by adding the diode. Here's the diagram I just made for this:
Senior User
Joined: Mar 2010
Posts: 419
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From: Timmins, Ontario, Canada
Hmmm, I never have any effects like that. It drives the same as when its cold.
Driving with high idle and timing advance would be the same as driving it cold, would it not? That's the way the factory setup would have it until the engine is warmed up.
Driving with high idle and timing advance would be the same as driving it cold, would it not? That's the way the factory setup would have it until the engine is warmed up.
Postmaster
Joined: Apr 2009
Posts: 4,086
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From: Malahat/Cowichan Valley
they are only on till it reaches about 120, then it is a noticeable click off. The timing advance being on all the time would be interesting, not like being just cold, it would significantly advance timing all the time, might be good for some old trucks but would not be recommended haha. The high idle, yeah you dont want that on all the time either. If you dont notice a difference when you press the pedal in the early morning and feel a click then you are not in working order. I wouldnt say you need it in warmer areas, like south florida or similar but if it gets cold, you will definitely need it to work, it makes a world of difference.
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Postmaster
Joined: Apr 2008
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The fast idle can stay on for as long as you want it, no downside to that other than you have to be a bit heavier on the brake pedal to hold her still at a red light. My truck idles at 800 and my fast idle is 1100 rpms, I can actually bring it up to 1400 rpms if I want to but there's no need for this as I can run my York at any engine speed with the hand-throttle setup so I'm leaving the fast-idle solenoid take care of cold-starts only.
Senior User
Joined: Mar 2010
Posts: 419
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From: Timmins, Ontario, Canada
I definitely notice the difference, the whole reason I wired that was because if I turn the engine off for an hour in February the coolant is still too hot to go into cold start mode but the truck will stall at idle without it, until it has a chance to warm back up. I'll also drive for a few minutes before the truck will come out of cold start most of the year.
Now saying it drives like its cold; I only enable this switch when it IS cold, I've never flipped it with a warm engine; at least now I know not to! The light in that loop is supposed to tell you when the temp switch suggests you need the advance. I'll add the diode as protection to that circuit!
We have LCAM's setup on our land cruisers at work, its great for the winter, or running a generator, especially on a Japanese diesel... they don't design with cold in mind! I'd love to be able to find the parts to transfer over.
Now saying it drives like its cold; I only enable this switch when it IS cold, I've never flipped it with a warm engine; at least now I know not to! The light in that loop is supposed to tell you when the temp switch suggests you need the advance. I'll add the diode as protection to that circuit!
We have LCAM's setup on our land cruisers at work, its great for the winter, or running a generator, especially on a Japanese diesel... they don't design with cold in mind! I'd love to be able to find the parts to transfer over.
Postmaster
Joined: Apr 2008
Posts: 4,802
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Google "vernier throttle cable" and you'll find many listed for sale, prices are very reasonable as well. Most will come with a long cable and sheathing that you can run to your IP directly, which is a good redundancy for in case your factory throttle cable snaps and you're ways away from home, but for what I paid for mine ($5) and the junkyard I ain't complaining, and in case of an emergency I can ramp up my engine speed big time by simply readjusting the fast-idle solenoid. Then to mount the thing under the dash you'll probably need to make some brackets similar to mine, i used 1/8" flat stock and it works great - had to replace the two factory steering column bolts with longer ones to account for the bracket's thickness, and the plastic cover panel needed cut, but that's no big deal really...
And yes, add the diode to your system to isolate the cold-advance solenoid from the fast-idle one, when you're running in manual mode, I can't see your diagram easily (do you have a larger view of it?) so I can't suggest as to where exactly to wire it in, but you seem to have a good understanding of how electrical components work so I'm sure you'll figure out a suitable location for it.
And yes, add the diode to your system to isolate the cold-advance solenoid from the fast-idle one, when you're running in manual mode, I can't see your diagram easily (do you have a larger view of it?) so I can't suggest as to where exactly to wire it in, but you seem to have a good understanding of how electrical components work so I'm sure you'll figure out a suitable location for it.
Post Fiend
Joined: Feb 2009
Posts: 8,005
Likes: 7
From: Ottawa, Ontario
He uses it as a cruise control to. Jams it in the floor and pulls out the **** and keeps the throttle in the floor, don't worry, truck doesn't do more than ~65mph. lol
Posting Guru
Joined: Jan 2010
Posts: 1,665
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From: Terre Haute, IN
BTW Otahyoni, some people are trying to convince me to build a flatbed when/if mine rusts out, and up until i saw ur truck i didnt like the idea. Now im thinking it looks good with the big tires! What size tires are they, and any lift? Mine is the supercab so i wonder what it would look like... Maybe someday...
Its 4" lift front and rear, 37" HMMWV tires... Homemade bed could use some more tire room, but it's easy enough to fix...
Posting Guru
Joined: Feb 2008
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From: Lubbock, Texas
This is my dumb question of the day (and I think I know the answer).
I dont think it would work due to the lack of electronics on an idi but will a powerstroke AIC/ACPM work on an idi?
I dont forsee it working on an idi but is there a way to just have it display the rpm? I would think just reading the rpm wouldnt require all the electronics like actually changing the rpm.
I dont think it would work due to the lack of electronics on an idi but will a powerstroke AIC/ACPM work on an idi?
I dont forsee it working on an idi but is there a way to just have it display the rpm? I would think just reading the rpm wouldnt require all the electronics like actually changing the rpm.