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1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks Discuss the Early Eighties Bullnose Ford Truck

300-6 Idle miss

 
  #91  
Old 02-10-2019, 08:26 PM
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Originally Posted by 1981 F100 View Post
Carburetor has been adjusted, several times with no noticeable results. I did observe a broken off exhaust manifold bolt at the front of the engine, but I doubt that would have anything to do with it
exhauast manifold and intake manifold share a gasket, maybe.

an intake manifold gasket leak could cause your symptoms as it my run well on fast idle because it is richer, compensating for the leak.

also I rebuild every carb completely on a vehicle with idling issues. There is too much that can go wrong with an old carb to bother troubleshooting the rest.
 
  #92  
Old 02-10-2019, 08:35 PM
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Originally Posted by jackietreehorn View Post


exhauast manifold and intake manifold share a gasket, maybe.

an intake manifold gasket leak could cause your symptoms as it my run well on fast idle because it is richer, compensating for the leak.

also I rebuild every carb completely on a vehicle with idling issues. There is too much that can go wrong with an old carb to bother troubleshooting the rest.
The fact that it runs better off idle could be the intake gasket too, I looked at the top edge of the gasket, and it looks like this "~~~~~~~~~~~~~ " In other words, it's not flat against the head like it should be
 
  #93  
Old 02-10-2019, 10:35 PM
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Originally Posted by 1981 F100 View Post
Carb was a 1 year old Holley remanufactured unit, came with the truck. Was clean inside, just wiped out the bowl. I have the idle speed screw all the way in, still idling very slow and rough. I took idle screw out and sprayed the passage with carb cleaner, it didn't do anything to help. This is just at idle, as I drive it runs smooth.

I had thought, that my pickup coil in the Duraspark dizzy I just put in might be bad, but this rough idle problem was present with the previous hacked up EEC-IV setup

I thought intake gasket, but spraying carb cleaner around the ports didn't change the idle quality any
When you say "wiped out" was that the picture in the other post what you got out?
If so rebuild that carb as that junk got pulled into the idle circuit.
Also you said "idle speed screw" did you mean to say speed mix screw? If so then the carb is the issues and needs to be rebuilt to get cleaned out.

Originally Posted by 1981 F100 View Post
Carburetor has been adjusted, several times with no noticeable results. I did observe a broken off exhaust manifold bolt at the front of the engine, but I doubt that would have anything to do with it
That is because the carb has dirt in the idle circuit and why making adjustments don't do any thing.

Originally Posted by 1981 F100 View Post
The fact that it runs better off idle could be the intake gasket too, I looked at the top edge of the gasket, and it looks like this "~~~~~~~~~~~~~ " In other words, it's not flat against the head like it should be
It runs better because you are no longer on the idle circuit. If the high speed side had dirt in it then when you give it gas it would not run but only idle.
Dave ----

 
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Old 02-10-2019, 10:37 PM
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If you have access to compressed air try and pull the idle mixture screw out and spray carb cleaner in again then blow air thru it maybe that will get the dirt out of the idle circuit.
Dave ----
 
  #95  
Old 02-10-2019, 10:52 PM
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Originally Posted by FuzzFace2 View Post
If you have access to compressed air try and pull the idle mixture screw out and spray carb cleaner in again then blow air thru it maybe that will get the dirt out of the idle circuit.
Dave ----
Sadly I do not as I live in an apartment complex. I accidentally pulled a vacuum hose while it was idling, and the idle speed came up, and smoothed out like normal, the second I put it back on, it went right back to very rough. Has to be sucking major air somewhere....
 
  #96  
Old 02-10-2019, 11:15 PM
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Originally Posted by 1981 F100 View Post
Sadly I do not as I live in an apartment complex. I accidentally pulled a vacuum hose while it was idling, and the idle speed came up, and smoothed out like normal, the second I put it back on, it went right back to very rough. Has to be sucking major air somewhere....
Which line did you pull?
 
  #97  
Old 02-11-2019, 05:43 AM
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Originally Posted by 1981 F100 View Post
Sadly I do not as I live in an apartment complex. I accidentally pulled a vacuum hose while it was idling, and the idle speed came up, and smoothed out like normal, the second I put it back on, it went right back to very rough. Has to be sucking major air somewhere....
Maybe a can of air like for cleaning computer parts will work? I just don't know if it will have enough PSI behind it to push the blockage out. Did you add any Sea Foam to the gas tank? I have had good luck with Sea Foam in a wood chipper that the carb sat with fuel in it for years. Even after cleaning did not want to run just right. A little in the tank each time I filled it and by the 3rd tank ran like new.

I am almost sure you dont have a vacuum leak.
With the motor up to temp did you pull the air filter, vacuum lines plugged, motor running try covering the carb a little at a time? If so and there was a change in the idle then I would say maybe a vacuum leak. Again I don't think you will find it makes a change.
Because you are there open the throttle fast and release it and cover the carb as the RPM comes back down but don't let it stall. Do this a few times and hope it pulls the crap in the carb thru it and will idle then.
Dave ----
 
  #98  
Old 02-11-2019, 05:48 AM
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Originally Posted by Kramercd View Post
Which line did you pull?
Cruise control servo hose, but did similar with the vac advance and other hoses
 
  #99  
Old 02-11-2019, 06:33 AM
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Originally Posted by FuzzFace2 View Post
Maybe a can of air like for cleaning computer parts will work? I just don't know if it will have enough PSI behind it to push the blockage out. Did you add any Sea Foam to the gas tank? I have had good luck with Sea Foam in a wood chipper that the carb sat with fuel in it for years. Even after cleaning did not want to run just right. A little in the tank each time I filled it and by the 3rd tank ran like new.

I am almost sure you dont have a vacuum leak.
With the motor up to temp did you pull the air filter, vacuum lines plugged, motor running try covering the carb a little at a time? If so and there was a change in the idle then I would say maybe a vacuum leak. Again I don't think you will find it makes a change.
Because you are there open the throttle fast and release it and cover the carb as the RPM comes back down but don't let it stall. Do this a few times and hope it pulls the crap in the carb thru it and will idle then.
Dave ----
Yes I had sea foam in the main front tank on the truck. The temporary one I have hooked up was spotless inside so it didn't really need it. I pulled a couple vac lines and idle came up,and smoothed out. Will try covering the carb with my hand again and see what happens
 
  #100  
Old 02-11-2019, 06:45 AM
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Originally Posted by 1981 F100 View Post
Cruise control servo hose, but did similar with the vac advance and other hoses
Vacuum advance hose should not do anything if the hose is hooked to ported vacuum and the truck is idling at the right speed.
I say this because there should not be any vacuum on that line at idle.

Originally Posted by 1981 F100 View Post
Yes I had sea foam in the main front tank on the truck. The temporary one I have hooked up was spotless inside so it didn't really need it. I pulled a couple vac lines and idle came up,and smoothed out. Will try covering the carb with my hand again and see what happens
The Sea Foam is not so much to clean the tank but the whole fuel system - read carb.
I would add Sea Foam to that "test fuel tank". If the label said to add say 2 oz to a gal of fuel I would add 4 oz to a gal. hit it hard with extra to get that carb cleaned inside.
Dave ----
 
  #101  
Old 02-11-2019, 12:36 PM
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Originally Posted by 1981 F100 View Post
Cruise control servo hose, but did similar with the vac advance and other hoses
idle speed increases and idle smooths out when you CREATE a massive air leak? So, whats your air filter look like? Fuel mix too rich?
 
  #102  
Old 02-11-2019, 01:23 PM
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Originally Posted by FuzzFace2 View Post
I saw a post earlier a member could not find a vacuum leak using carb cleaner so he used the smoke test for locating the leak.
You seal off the carb opening with duct tape, find a hose going to the intake like that brake booster hose, and find a friend that smokes or get a cheap cigar light up and blow the smoke in the hose filling the intake a few times maybe 3 times looking for smoke coming out where it should not.
Dave ----
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  #103  
Old 02-11-2019, 04:03 PM
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Replacement E3TE-AAA carb for my truck


Spotless float bowl
I think it's carb replacement time, while I was out today it got so bad I could barely get 15 mph out of it. So bought a nice clean E3TE-AAA carb for $30 and a kit. plus a pail of carb cleaner. Took top off and the bowl was spotless! Not bad for a $30 boneyard find. Now, how long do I soak everything in the carb cleaner?
 
  #104  
Old 02-11-2019, 04:54 PM
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It depends on how dirty it is.
Mine was not really dirty just leaked from drying out when the truck was apart.
Think I did it for about 2 hours, looked it over used a acid brush to hit bad places, soak another 30 minutes then pulled and rinsed.

I may have tried that carb just to see how it ran being it looked that good and maybe rebuilt the one from your truck.
Dave - - - -
 

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