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how to adjust idle?

8940 Views 13 Replies 10 Participants Last post by  Old 'n Rusty
i don't have a tach but it seems my truck is idling a little to high, when i put it in gear it tries to jump forward or backward, and sounds to high, where do i adjust it at?
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Simple as can be.

The throttle sitting on the top front of the injection pump rests on a screw that lies in between the injection pump and the head. To change idle speed you back the screw out or thread it forward.

Simple doesn't mean easy, however. The location of the screw makes it difficult to get to; I'd recommend knocking the lock nut loose with a screw driver, dousing the thing in the penetrating agent of your choice (Liquid Wrench or Aerokroil), and then using a 1/4" boxend wrench to pry onto the end of the screw and twist it.
 

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Simple as can be.

The throttle sitting on the top front of the injection pump rests on a screw that lies in between the injection pump and the head. To change idle speed you back the screw out or thread it forward.

Simple doesn't mean easy, however. The location of the screw makes it difficult to get to; I'd recommend knocking the lock nut loose with a screw driver, dousing the thing in the penetrating agent of your choice (Liquid Wrench or Aerokroil), and then using a 1/4" boxend wrench to pry onto the end of the screw and twist it.
I turned mine around when I had the pump off. I can turn the truck off, push the throttle lever to full throttle and turn the screw no problem. It's about to come off though since it's purt near bottomed out. Once I play with the fuel screw more it'll have to come out. :thumbsup:
 

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I turned mine around when I had the pump off. I can turn the truck off, push the throttle lever to full throttle and turn the screw no problem. It's about to come off though since it's purt near bottomed out. Once I play with the fuel screw more it'll have to come out. :thumbsup:
eventually it will just rest on the afc housing of the pump if yours already isnt
 

· I bleed Diesel
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mynes resting on the thing already. and it is was a virgin till today. i didnt realize how much a stock truck increases. i always did mods
 

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eventually it will just rest on the afc housing of the pump if yours already isnt
Yeah right now I have the nut on the very end of the front part of the idle screw so it's only about 1/2" from being bottomed out. I have about 1/2 a turn left on my fuel screw so eventually the idle screw will come out. This way all I gotta do is pull the throttle assembly off and pull it out.
 

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Out of curiosity, what is the rule of thumb to knowing how low to take the idle. After turning up my pump I was clunking into gears from an obviously too high idle. Since then I''ve ground it down, but I think I took it too low. The truck really vibrates in idle now, and the 4wd shifter moves sideways about an inch from the vibration.

I assume it's too low now, but without a tach...how does one tell?
 

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They sell a tool, don't know how expensive it is or even what it's called but you place it on any part of your engine that vibrates. A wheel turned on the tool pushes a wire with a loop on the end out and as soon as the end loop starts spinning in a circle you look at the tool and a chart tells you what RPMs you're spinning. It's a pretty cool tool. Now that I say that I also have to say it didn't work for me...hehe. It told me my RPMs were at something like 3k at idle but by the shaking and rough running of the truck it was easy to tell it was way too low... Long story short, might be easier to estimate.
 

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They sell a tool, don't know how expensive it is or even what it's called but you place it on any part of your engine that vibrates. A wheel turned on the tool pushes a wire with a loop on the end out and as soon as the end loop starts spinning in a circle you look at the tool and a chart tells you what RPMs you're spinning. It's a pretty cool tool. Now that I say that I also have to say it didn't work for me...hehe. It told me my RPMs were at something like 3k at idle but by the shaking and rough running of the truck it was easy to tell it was way too low... Long story short, might be easier to estimate.
:drool:

Hand-held optical tachometers off eBay cost under $50 for cheap ones.
 

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You don't really need a tach to set idle. It sounds like you have an automatic. Increase rpm's till the truck starts to creep ahead and then back it off till it doesn't anymore. The only down side to a higher idle is this automatic issue. Too low causes all kinds of problems. I don't think it does the crank any good and it rattled my rad so hard it sprung a leak. Diesels use little fuel at idle because they are not trying to pull air past a closed throttle plate like in a gasoline engine.

A highish idle helps cool down the turbo, circulates oil at better pressure.

In the summer, it even helps the AC cope better. In the winter, the warm-up is faster.
 
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