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

300-6 Idle miss

 
  #61  
Old 02-09-2019, 05:33 PM
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This fitting where the power brake booster hose attaches is at the adapter where the carb mounts to. Sounds like a vacuum leak, but for the life of me I don't know.
 
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Old 02-09-2019, 05:59 PM
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Originally Posted by 1981 F100 View Post
This fitting where the power brake booster hose attaches is at the adapter where the carb mounts to. Sounds like a vacuum leak, but for the life of me I don't know.
When I first got my truck I checked for vacuum leaks by spraying carb and choke. 0 vac leaks except I had several. Found the one where the warm air side of the climatic choke plugs in on accident. Sucked my thumb in and I didn't think it was going to give it back. I've never had much luck finding vacuum leaks with carb and choke.
 
  #63  
Old 02-09-2019, 06:07 PM
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If cylinder compression is good as you say then a mechanic's vacuum gauge hooked to manifold would likely give some very useful clues. Vacuum gauges are a must have for troubleshooting.

As far as ignition, find somebody who has an ignition scope. Just for grins, just to eliminate the ignition system as a source of trouble.

 
  #64  
Old 02-09-2019, 06:12 PM
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Originally Posted by 1981 F100 View Post
This fitting where the power brake booster hose attaches is at the adapter where the carb mounts to. Sounds like a vacuum leak, but for the life of me I don't know.
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.

Now I went thru all 4 pages and I did not see anything about you pulling the EGR and making a block off plate and putting the valve back on to see what happens.
The valve could be stuck open a little from carbon build up and cause a leak that the smoke test cant see. If the block off plate is made right it will not be seen and can be left in place, use a pop can for the plate.
BTW the smoke test did find a vacuum leak at the EGR valve diaphragm.
Dave ----
 
  #65  
Old 02-09-2019, 06:52 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.

Now I went thru all 4 pages and I did not see anything about you pulling the EGR and making a block off plate and putting the valve back on to see what happens.
The valve could be stuck open a little from carbon build up and cause a leak that the smoke test cant see. If the block off plate is made right it will not be seen and can be left in place, use a pop can for the plate.
BTW the smoke test did find a vacuum leak at the EGR valve diaphragm.
Dave ----
Has no EGR. the carb mounting adapter on my engine is a non EGR one
 
  #66  
Old 02-09-2019, 07:30 PM
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Originally Posted by 1981 F100 View Post
Has no EGR. the carb mounting adapter on my engine is a non EGR one
How is that? Got a picture of this?
Are you sure it is sealing? I know of a carb adaptor on L6 motor, stock intake to holly v2 carb that you have to check really really close as it leaks at the adaptor to intake bolt holes that cause a vacuum leak.
Dave ----
 
  #67  
Old 02-09-2019, 08:00 PM
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Originally Posted by FuzzFace2 View Post
How is that? Got a picture of this?
Are you sure it is sealing? I know of a carb adaptor on L6 motor, stock intake to holly v2 carb that you have to check really really close as it leaks at the adaptor to intake bolt holes that cause a vacuum leak.
Dave ----
Ask and ye shall receive, here is a photo

 
  #68  
Old 02-09-2019, 08:09 PM
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is that a boogered plug, excessive welding, or quicksteel putty?
 
  #69  
Old 02-09-2019, 08:12 PM
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Originally Posted by Kramercd View Post
is that a boogered plug, excessive welding, or quicksteel putty?
Danged if I know, that was on the truck when I bought it. I can take it off in the morning for a closer look, I wonder if that was an EGR one that was butchered? They have the power brake hose going into it, instead of the vacuum tree on the manifold. Heck this could be the culprit
 
  #70  
Old 02-09-2019, 08:40 PM
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Originally Posted by 1981 F100 View Post
Danged if I know, that was on the truck when I bought it. I can take it off in the morning for a closer look, I wonder if that was an EGR one that was butchered? They have the power brake hose going into it, instead of the vacuum tree on the manifold. Heck this could be the culprit
It is. been chopped and hole has been plugged. Hit a high spot with a file, if it is epoxy based it could expand and contract and lose it's seal. Could be hiding a vac leak.
 
  #71  
Old 02-09-2019, 08:44 PM
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Originally Posted by Kramercd View Post
It is. been chopped and hole has been plugged.
So go get a good EGR adapter, then make an EGR blockoff plate? Maybe that will solve this issue
 
  #72  
Old 02-09-2019, 08:58 PM
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Originally Posted by 1981 F100 View Post
Danged if I know, that was on the truck when I bought it. I can take it off in the morning for a closer look, I wonder if that was an EGR one that was butchered? They have the power brake hose going into it, instead of the vacuum tree on the manifold. Heck this could be the culprit
Originally Posted by Kramercd View Post
It is. been chopped and hole has been plugged. Hit a high spot with a file, if it is epoxy based it could expand and contract and lose it's seal. Could be hiding a vac leak.
Or could do this when off

I picked up a freeze plug from the auto parts store that fit the port in the intake, a little sealer and drive it in.
I then put the EGR plate back in place so it looks like it works.

Check the gaskets between the plate, intake and carb.
Dave ----
 
  #73  
Old 02-09-2019, 09:07 PM
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I'll do that. Will have to go get another EGR adapter Monday at the boneyard. Maybe, I have this solved
 
  #74  
Old 02-10-2019, 08:08 AM
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Took off the boogered up adapter, and here are a couple photos of what I found. What size freeze plug would I need, to fill the hole in the intake, once I get a replacement adapter?
 
  #75  
Old 02-10-2019, 08:17 AM
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I would check year carb + base gaskets, they are more suspect to me than this patch. Are you sure that's Bondo and not quickstep/epoxy? Epoxy would seem to be a serviceable repair.

If not, start small and drill out with progressively larger bits until reveal the whole hole and go from there.
 

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