Rough Idle until warmed up - Ford Truck Enthusiasts Forums



Rough Idle until warmed up

Reply
 
 
 
Thread Tools Search this Thread
  #1  
Old 03-12-2010, 06:28 PM
mil2civ mil2civ is offline
New User
Thread Starter
 
Join Date: Mar 2010
Posts: 1
mil2civ is starting off with a positive reputation.
Rough Idle until warmed up

Recently purchased '85 E350 w/300 V6. Starts like a champ but idle rough upon start. Sometimes dies if I don't keep the revs up. However, when she is warmed up she idles just fine. Faulty electric choke?
Reply With Quote
  #2  
Old 03-12-2010, 06:33 PM
dustybumpers's Avatar
dustybumpers dustybumpers is offline
Posting Legend
 
Join Date: May 2008
Location: In my own world
Posts: 56,569
dustybumpers has a superb reputationdustybumpers has a superb reputationdustybumpers has a superb reputationdustybumpers has a superb reputationdustybumpers has a superb reputationdustybumpers has a superb reputationdustybumpers has a superb reputationdustybumpers has a superb reputationdustybumpers has a superb reputationdustybumpers has a superb reputationdustybumpers has a superb reputation
metal vaccume line that goes from the choke stove down to the exhaust manifold is probably rusted off.
Reply With Quote
  #3  
Old 09-09-2010, 02:26 PM
Superred2's Avatar
Superred2 Superred2 is offline
Senior User
 
Join Date: May 2010
Location: Spartanburg, SC
Posts: 346
Superred2 is starting off with a positive reputation.
How would you replace that metal vacuum line if it was rusted off? Mine was broken off at the exhaust manifold and so I removed it. Can you buy a replacement for it and how does it attach to the exhaust manifold?
Reply With Quote
  #4  
Old 09-09-2010, 04:19 PM
dustybumpers's Avatar
dustybumpers dustybumpers is offline
Posting Legend
 
Join Date: May 2008
Location: In my own world
Posts: 56,569
dustybumpers has a superb reputationdustybumpers has a superb reputationdustybumpers has a superb reputationdustybumpers has a superb reputationdustybumpers has a superb reputationdustybumpers has a superb reputationdustybumpers has a superb reputationdustybumpers has a superb reputationdustybumpers has a superb reputationdustybumpers has a superb reputationdustybumpers has a superb reputation
you would have to bend a new one out of brake line. it is a "pressure" fit,when you use a drill to get the old one out of the manifold, make sure the drill bit is same size as the tubing
Reply With Quote
  #5  
Old 09-09-2010, 06:00 PM
AbandonedBronco's Avatar
AbandonedBronco AbandonedBronco is offline
Moderator
 
Join Date: Dec 2007
Location: Boise, Idaho
Posts: 6,217
AbandonedBronco has a great reputation on FTE.AbandonedBronco has a great reputation on FTE.AbandonedBronco has a great reputation on FTE.AbandonedBronco has a great reputation on FTE.AbandonedBronco has a great reputation on FTE.
It doesn't screw into the manifold or anything. It's just a piece of tubing that exits the carb, and sits in an "indent" in the manifold. The carb being bolted down basically holds it in place.

Other things that may be causing the rough idle when cold though.

- Warped intake manifold. The warping causes a slight vacuum leak that seals itself up as the metal expands from the heat.

- Cracked vacuum lines (especially if you have those brittle color coded plastic ones). The engine is more sensitive to vacuum leaks when cold.

- Choke isn't open enough. Easy to tell, take the air filter off when the engine is cold, fully open and close the throttle and look at the choke plate. It should be about 1/16" - 1/8" open. Any less, and it'll be difficult to start. Any more, and it'll be getting too much cold air. Adjust it by loosening the choke housing and twisting. Once done, fully warm up the engine and be sure the choke is 100% open. Being 100% open after fully warmed up is more important in the long run.
Reply With Quote
  #6  
Old 09-09-2010, 07:04 PM
Superred2's Avatar
Superred2 Superred2 is offline
Senior User
 
Join Date: May 2010
Location: Spartanburg, SC
Posts: 346
Superred2 is starting off with a positive reputation.
Now explain what the tube does that runs from the manifold to the carb? Is that for carb heat? Does it create a vacuum? Mine is off and it runs fine. I didn't know if it was needed or not.
Reply With Quote
  #7  
Old 09-09-2010, 07:53 PM
AbandonedBronco's Avatar
AbandonedBronco AbandonedBronco is offline
Moderator
 
Join Date: Dec 2007
Location: Boise, Idaho
Posts: 6,217
AbandonedBronco has a great reputation on FTE.AbandonedBronco has a great reputation on FTE.AbandonedBronco has a great reputation on FTE.AbandonedBronco has a great reputation on FTE.AbandonedBronco has a great reputation on FTE.
The tube that runs down is to aid in warming the choke up. When I got mine, it had both that and an electric choke that worked together. A small vacuum pulls air through the tube and pulls warm air up from the manifold.

Mine was rusted out when I got mine and I have 15 winters here and I never missed it. I did eventually fix it, but didn't notice much difference.
Reply With Quote
  #8  
Old 09-09-2010, 08:45 PM
Superred2's Avatar
Superred2 Superred2 is offline
Senior User
 
Join Date: May 2010
Location: Spartanburg, SC
Posts: 346
Superred2 is starting off with a positive reputation.
Would it cause an issue if you just plugged it up?
Reply With Quote
  #9  
Old 09-10-2010, 02:59 PM
1986F150six 1986F150six is offline
Post Fiend
 
Join Date: Jul 2009
Location: Sheffield, AL
Posts: 5,086
1986F150six is a splendid one to behold1986F150six is a splendid one to behold1986F150six is a splendid one to behold1986F150six is a splendid one to behold1986F150six is a splendid one to behold1986F150six is a splendid one to behold1986F150six is a splendid one to behold
With it plugged up [most people simply crimp the tube where it enters the choke housing], the choke takes longer to fully open up. This occurs every time you start your "not warm" engine. This wastes fuel and theoretically allows more oil to be washed off the cylinder walls, which will shorten engine life.

If you do this, be sure to put a rubber cap on the open port at the top of the carburetor, where the clean air is drawn from to provide air which was to be pulled through the tube which is heated by the exhaust manifold prior to entering the choke housing.

By the way, there is a small vacuum port inside the choke housing, so if the line is not closed, one will have a vacuum leak.
Reply With Quote
  #10  
Old 09-12-2010, 08:15 PM
Superred2's Avatar
Superred2 Superred2 is offline
Senior User
 
Join Date: May 2010
Location: Spartanburg, SC
Posts: 346
Superred2 is starting off with a positive reputation.
So today, I decided to do the deed. I took some brake line and customed fitted a line from the carb to the manifold. I drilled it so the fit is snug and it worked out well. Do you think it will need any heat tape on it?

Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
6.9 rough idle & surging but starts & runs good??? ZombiePopper Pre-Power Stroke Diesel (7.3L IDI & 6.9L) 12 10-01-2014 11:59 AM
02 7.3 running rough need help txwavman 1999 to 2016 Super Duty 5 06-17-2014 11:47 AM
70 302 w 2100 carb, high idle tuning secrets needed acreature 1967 - 1972 F-100 & Larger F-Series Trucks 3 11-26-2012 06:07 AM
Exhaust leak cause rough idle? jejenkins417 Excursion - King of SUVs 6 06-25-2011 06:13 PM
idling rough 7.3 bassin88 1999 to 2016 Super Duty 1 10-11-2009 07:50 AM


Go Back   Ford Truck Enthusiasts Forums >

Tags
200, 300, 49l, carb, choke, electric, faulty, ford, fully, holley, idle, inline, rough, runs, warmed

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Forum Jump


All times are GMT -5. The time now is 06:16 AM.