duraspark conversion idle issue
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Junior User
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duraspark conversion idle issue
Hi guys. Just finishing up a duraspark conversion on my 86 f150 300. Engine started fine but was idling way too high in park. I turned the idle down a little and when i put it in gear it drops so low it wants to die. So basicly it idling really high in park, really low in gear. Any ideas? Thanks.
Fleet Mechanic
Joined: Jul 2011
Posts: 1,916
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I'm assuming you have an automatic transmission?
Set your high idle when the truck is cold. Make sure the choke is set properly and that none of the linkages are binding/bound. As the truck comes off of high idle as the choke opens it should be slowly coming down in steps. Bump the gas to knock it off the high-idle cam and there's your curb idle. Set your curb idle speed high enough that it's not going to die when you put it in gear.
Then, have someone sit up in the seat and make SURE they can hold the brake, and set the parking brake while you're at it. Don't forget to block the wheels.
Put it in gear, holding it in place, and then set your curb idle speed.
Let us know what you find.
I don't think it'll be a problem with the conversion itself. Something like this is the carb or linkages I would think.
Check for vacuum leaks too.
Set your high idle when the truck is cold. Make sure the choke is set properly and that none of the linkages are binding/bound. As the truck comes off of high idle as the choke opens it should be slowly coming down in steps. Bump the gas to knock it off the high-idle cam and there's your curb idle. Set your curb idle speed high enough that it's not going to die when you put it in gear.
Then, have someone sit up in the seat and make SURE they can hold the brake, and set the parking brake while you're at it. Don't forget to block the wheels.
Put it in gear, holding it in place, and then set your curb idle speed.
Let us know what you find.
I don't think it'll be a problem with the conversion itself. Something like this is the carb or linkages I would think.
Check for vacuum leaks too.
Thread Starter
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Junior User
Joined: Apr 2006
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i do have the non-feedback carb. the vacum advance is hooked up to the port on the carb on the left side near the top as you are looking at it from the front of the truck. the vacuum advance being hooked up wrong does sound like a good possibility. i havent had a chance to check it yet. i will in the morning. im also having a issue with it being hard to turn over, but seems to run fine when it starts. those 2 issues seem like they could be connected. do you think my timing could be retarted making it hard to start ,but once its running and has vacum to the advance at idle that it would sound like it was running strong? i made the mistake of timing it by ear without disconnecting the vacum advance.
Thread Starter
|
Junior User
Joined: Apr 2006
Posts: 77
Likes: 0
I'm assuming you have an automatic transmission?
Set your high idle when the truck is cold. Make sure the choke is set properly and that none of the linkages are binding/bound. As the truck comes off of high idle as the choke opens it should be slowly coming down in steps. Bump the gas to knock it off the high-idle cam and there's your curb idle. Set your curb idle speed high enough that it's not going to die when you put it in gear.
Then, have someone sit up in the seat and make SURE they can hold the brake, and set the parking brake while you're at it. Don't forget to block the wheels.
Put it in gear, holding it in place, and then set your curb idle speed.
Let us know what you find.
I don't think it'll be a problem with the conversion itself. Something like this is the carb or linkages I would think.
Check for vacuum leaks too.
Set your high idle when the truck is cold. Make sure the choke is set properly and that none of the linkages are binding/bound. As the truck comes off of high idle as the choke opens it should be slowly coming down in steps. Bump the gas to knock it off the high-idle cam and there's your curb idle. Set your curb idle speed high enough that it's not going to die when you put it in gear.
Then, have someone sit up in the seat and make SURE they can hold the brake, and set the parking brake while you're at it. Don't forget to block the wheels.
Put it in gear, holding it in place, and then set your curb idle speed.
Let us know what you find.
I don't think it'll be a problem with the conversion itself. Something like this is the carb or linkages I would think.
Check for vacuum leaks too.
Lead Driver
Joined: Jul 2009
Posts: 6,477
Likes: 19
From: Sheffield, AL
vboxingguy,
You mentioned that the vacuum advance line is connected to the port on the carb on the left side near the top... I have seen carburetors [Carter YF or YFA], depending on year of manufacture, with multiple vacuum ports; some for vacuum advance and others for emission components. Take a vacuum gauge and hook to each port separately, being sure the others are capped. You are looking for the one which has no vacuum @ curb idle speed to connect to your distributor.
You mentioned that the vacuum advance line is connected to the port on the carb on the left side near the top... I have seen carburetors [Carter YF or YFA], depending on year of manufacture, with multiple vacuum ports; some for vacuum advance and others for emission components. Take a vacuum gauge and hook to each port separately, being sure the others are capped. You are looking for the one which has no vacuum @ curb idle speed to connect to your distributor.
Fleet Mechanic
Joined: Jul 2011
Posts: 1,916
Likes: 4
This is an old picture where I was still dressing up the engine bay and all.
The yellow circle circles the vacuum port where your vacuum advance goes. You can't physically see the port, but it's right up under that plate (which is the TSP Dashpot). Ported vacuum is ABOVE the throttle plate, Manifold vacuum is BELOW the throttle plate. The plate on the top that's partway open is the choke.
Blue is the bowl vent.
Red is the fresh air port for the thermostatic hot air choke.
Put your vacuum advance to the port where I put the yellow circle.
EDIT:
I try to save as many photos as I can for information and record keeping stuff that I can use later for reference (and in this case, to help someone out).
The yellow line in this photo is where the vacuum advance port is on a YFA Carter. It's next to where the throttle linkage hooks up. The yellow line in the photo highlights the actual advance line.
The yellow circle circles the vacuum port where your vacuum advance goes. You can't physically see the port, but it's right up under that plate (which is the TSP Dashpot). Ported vacuum is ABOVE the throttle plate, Manifold vacuum is BELOW the throttle plate. The plate on the top that's partway open is the choke.
Blue is the bowl vent.
Red is the fresh air port for the thermostatic hot air choke.
Put your vacuum advance to the port where I put the yellow circle.
EDIT:
I try to save as many photos as I can for information and record keeping stuff that I can use later for reference (and in this case, to help someone out).
The yellow line in this photo is where the vacuum advance port is on a YFA Carter. It's next to where the throttle linkage hooks up. The yellow line in the photo highlights the actual advance line.
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