Idle mixture questions
Thread Starter
|
Senior User
Joined: Nov 2008
Posts: 212
Likes: 1
Idle mixture questions
I am trying to adjust my mixture at low idle. When I have the screw backed out only about 1/2 turn the engine begins to pick up speed and run smoothly. The problem is there is no change between 1 turn or until the screw falls out. It has been suggested that the needle valve venturi may be blocked from when I cleaned and rebuilt the carb. If I remove the screw entirely and put my finger over the hole shouldn't there be a slight vacuum? Can I squirt solvent in there and blow it out with mild compressed air? Your thoughts?
Postmaster
Joined: Jul 2001
Posts: 4,956
Likes: 10
From: MD
What do you mean, "low idle"?
If the idle mixtures don't change whenever you adjust till it closes or falls off the carburetor, it's a pretty good indicator you have a bad vacuum leak.
If it does change behavior from closed to 1 turn, then it sounds OK. It's easy and accurate to adjust the idle mixtures if you use a vacuum gauge.
If the idle mixtures don't change whenever you adjust till it closes or falls off the carburetor, it's a pretty good indicator you have a bad vacuum leak.
If it does change behavior from closed to 1 turn, then it sounds OK. It's easy and accurate to adjust the idle mixtures if you use a vacuum gauge.
Thread Starter
|
Senior User
Joined: Nov 2008
Posts: 212
Likes: 1
"Low Idle" ...the idle mixture adjuster on the passenger side.
I do get an appreciable change from closed to 1 turn but I thought it should begin to stumble after becoming too rich.
I'm getting a vac guage later this week. Where can I find more explicit instructions on using the vac guage for mixture? I.E. where to hook the guage and what the readings should look like?
I do get an appreciable change from closed to 1 turn but I thought it should begin to stumble after becoming too rich.
I'm getting a vac guage later this week. Where can I find more explicit instructions on using the vac guage for mixture? I.E. where to hook the guage and what the readings should look like?
Postmaster
Joined: Jul 2001
Posts: 4,956
Likes: 10
From: MD
Curb idle?
Using a vacuum gauge is really simple. There are few animated illustrations on using a vacuum gauge on the internet. Hook the gauge to the manifold vacuum source, that would be the tree at the back of the engine.
If the engine is healthy, the needle should be steady. Adjust the idle mixture until it reads 17-21 Hg.
Using a vacuum gauge is really simple. There are few animated illustrations on using a vacuum gauge on the internet. Hook the gauge to the manifold vacuum source, that would be the tree at the back of the engine.
If the engine is healthy, the needle should be steady. Adjust the idle mixture until it reads 17-21 Hg.
Thread Starter
|
Senior User
Joined: Nov 2008
Posts: 212
Likes: 1
Thanks for the help Jermafenser. I got the vacuum guage and within 5 minutes had both mixtures dialed in. Initial vacuum was <15"Hg and a few turns and I was at 21"Hg with rock steady idle. Truck starts from cold and drives 100% better! This also solved my stalling at stop signs issue. Turns out it was not the carb float or a vacuum leak as I had suspected...just really poor mixture!
Postmaster
Joined: Jul 2001
Posts: 4,956
Likes: 10
From: MD
Trending Topics
Posting Guru
Joined: Nov 2008
Posts: 1,647
Likes: 3
From: Halifx Pa
How to Use and Interpret a Vacuum Gauge
I know you already got it tuned, but for those who search, and need a little more help, this a good overview.
I know you already got it tuned, but for those who search, and need a little more help, this a good overview.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Posting Guru
Joined: Nov 2008
Posts: 1,647
Likes: 3
From: Halifx Pa
Plus one there brother!!!
Just a side bar, today I hooked up my vacuum guage, and adjusted my idle, choke, air.fuel mix, and timing, and it really runs like a top now.
Since my rebuild, I had a little trouble with cold starts. After it was warmed up it started fine, but now it runs like a new truck!!!
Oh yeah, the vacuum is 17 hg now.
Just a side bar, today I hooked up my vacuum guage, and adjusted my idle, choke, air.fuel mix, and timing, and it really runs like a top now.
Since my rebuild, I had a little trouble with cold starts. After it was warmed up it started fine, but now it runs like a new truck!!!
Oh yeah, the vacuum is 17 hg now.
Thread
Thread Starter
Forum
Replies
Last Post
lee
FE & FT Big Block V8 (332, 352, 360, 390, 406, 410, 427, 428)
4
Aug 3, 2015 11:30 AM
JayzDaddy
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
8
Nov 28, 2014 07:43 PM
1984Ford300six
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
19
Aug 29, 2014 12:12 PM
D. DeBoer
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
4
Jul 12, 2014 07:38 PM
bryan_johnson
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
2
Jul 27, 2002 12:12 AM
