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Discussion Starter #1
So just the other day I was driving around town and when I came to a stop light I noticed that my 4bt was idling low and felt a little rough. I decided to drive home to park it since I wasn't sure what was going on and when I came to another light it was idling higher than normal.

Since then it either idles normal or it idles high.

My normal idle is around 920 rpm.
When it idled low (only happened once) it was around 750.
When it idles high it is around 1150.

The 4bt is totally stock and I have put over 10,000 miles on it without any problems. The only thing that has been done to it is that I recently installed a 3200 rpm spring. I only had a little over 100 miles on the spring install before this issue started. I didn't have any problems at all for the first 100 miles after the install.

Any suggestions on what the issue could be?

Another thing to add is that once when I tried to shut it off when it was idling high it wouldn't shut off. It acted like it was trying to shut off and started cutting out/shaking really bad until I put the key back in the run position.
 

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Electric or manual fuel lift pump? Normal idle is around 750-800 rpm. Did you or a shop install the gsk?
 

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Could be shut off solenoid or lift pump,
 

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Check the obvious also, binding linkage. My truck would idle high with the AC on, turned out to be stickly linkage caused by the extra heat under the hood when the AC was on.... Replaced the ball crank end and lubed everything ... fixed
 

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My truck has a bit of a hunting idle as well. My normal idle is set to ~775rpm and sometimes it'll idle down as low as 600rpm. When I put my motor in I had some starting issues and had my injectors tested. One of them tested bad at idle speed/flow, but was good at all other RPM. I suspect my issue is related to that injector.

Have the injectors ever been serviced / replaced?
 

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I've been dealing with the idle changing from day one, it will change +/- 100 rpm between hot and cold running. Don't know what causes it but my solution was to add a manual throttle to set the idle.
I try to maintain the factory recommended idle, 800rpm
 

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Discussion Starter #7
It has a manual lift pump. I was the one that installed the spring. The injectors, pump, and engine were all rebuilt before I installed the 4bt in the truck which was about 10,000 miles ago. When it first started to idle high I thought there was an issue with the linkage but I checked it while it was running and it is fine. Before the install my idle was right around 850, it raised to 920 after the install. I decided to leave it there because it seemed to feel smoother at idle (I have read of people bumping their idle up to around 1000 because it feels smoother).

I am wondering if this issue is somehow related to the spring install seeing that it started happening shortly after it was done, but I don't understand what could cause it. It is really strange that it first idled low (and almost felt like it had a miss) and now it either idles fine or high. Anymore ideas?
 

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It has a manual lift pump. I was the one that installed the spring. The injectors, pump, and engine were all rebuilt before I installed the 4bt in the truck which was about 10,000 miles ago. When it first started to idle high I thought there was an issue with the linkage but I checked it while it was running and it is fine. Before the install my idle was right around 850, it raised to 920 after the install. I decided to leave it there because it seemed to feel smoother at idle (I have read of people bumping their idle up to around 1000 because it feels smoother).

I am wondering if this issue is somehow related to the spring install seeing that it started happening shortly after it was done, but I don't understand what could cause it. It is really strange that it first idled low (and almost felt like it had a miss) and now it either idles fine or high. Anymore ideas?
That's a good place to start. Since that was the last thing changed before the issue
 

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That's a good place to start. Since that was the last thing changed before the issue
I had variable idle with the stock gov spring and the 3200 gov spring.

Edit: Even after the IP was rebuild I still have the variable idle but to a lesser extent.
 

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I never ran my motor with the stock gov spring, but I do get hunting idle with my 3800rpm gov spring.

Do you have a fuel pressure gauge between the lift pump and the filter housing? The thought is that the lift pump is producing varying amounts of pressure, which causes the idle to change. Is that even possible?
 

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Possible. I think it might be from the various spring pressure of the stack of springs. The gov weights on the pumps mainly control the rpms. I know if one side on the ppump is different tension than the other it can cause the hunt or lope in the rpms. Did your VE stock GSK have any shims under the springs? If so did you remove them?
 

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Discussion Starter #12
Alright so I have an update. I have been driving it around trying to figure out a pattern. The high idle issue happens sporadically, it does not occur every time I drive it. I took three different rides through out the day and took note of idle rpm.
Today on the first run it idled normally at 920 rpm. The idle changed to 1110 right around the time that the coolant temp hit 165*. I pulled over and shut it off for a few seconds after letting the turbo cool and when I started it back up it was at normal idle (920 rpm).
Later in the day on my second run it idled normal for a while and then idled up to 958 rpm, then continued to 1010 rpms, and back down to 970 rpm (all readings taken at stop lights).
In the evening on the third run it idled normally for the whole ride.

It didn't do this before the spring change so do you guys think that the new spring is causing this? Should I be concerned or just keep running it?
 

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Check that, throttle return spring, throttle cable, and pedal. Next time it happens try pulling up in the pedal or manual move the lever back to the stop. Might have something binding up or sticking
 

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Discussion Starter #14
Yeah I have already checked all of that. The throttle cable/return spring is working flawlessly. I tried moving the lever back but it is always at the stop. I think whatever is happening is internal.
 

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Discussion Starter #15 (Edited)
I have an update. I have been driving the truck around and it has been idling fine. For the last few months I have been unable to shut it off unless I get out and do it manually with the lever on the pump. Today I decided to take the solenoid out so that I could gut it and put a cable on it for manual shut offs and I found this as well as many other pieces of metal blocking the plunger.

I can't get the picture to post so I can just tell you it is a bunch of metal pieces. They almost look like the top hat washer but there is no way that it could have some how came off of everything.
Where do I go from here? It is running fine now but am I in a position where I may start having issues in the future? What should I do?
 

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Discussion Starter #16
Do you guys think I need to have the pump torn down or injectors gone through? I am asking because it has been running fine.
 
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