Erratic Idle:
Thread Starter
|
Laughing Gas
Joined: Nov 2001
Posts: 968
Likes: 71
From: Cherryville,N.C.
Erratic Idle:
On my 239 flathead it will idle just fine then all a once the rpms will go up a couple of hundred and then it will idle back down to normal.I adjusted the idle mixture screws and seemed to help a lot,but still seems to do it every once and awhile.Any ideas on what else I should check?Thanks,Russell
Lead Driver
Joined: Apr 2002
Posts: 8,813
Likes: 13
From: Littleton, New Hampshire
Originally Posted by leonharu
What is an easy way to check for vacuum leak?
Posting Guru
Joined: Jan 2007
Posts: 1,527
Likes: 2
From: Grande Prairie, Alberta
Originally Posted by havi
starter fluid/ether.
I agree that this is the quickest way to detect the leak. If possible use a straw from WD40 can so you can get a more precise spray in the suspect areas.Have you placed a vacuum guage on the truck to see if you are within the correct range?
You also indicate that you adjusted the Idle mix screw on the carb and it helped alot. Which way did you adjust leaner or richer?
Thread Starter
|
Laughing Gas
Joined: Nov 2001
Posts: 968
Likes: 71
From: Cherryville,N.C.
I adjusted in until truck ran rough and vacuum started dropping then I backed out about 1/4 turn on one screw.On the other screw it don't seem to effect the idle and the screw is ran just about all the way in.I don't understand this!
Trending Topics
Lead Driver
Joined: Oct 1999
Posts: 6,774
Likes: 552
From: Kalispell, MT
The idle adjustments don't vary much from what I've seen. Turn them all the way in - careful to not crush the needles into the seats - then open 1 1/4 to 1 1/2 turns.
An old trick if you have junk in the carb orifices is to remove the air cleaner, rev it to between 1500 and 2K rpm and slap a piece of board on the carb top until it stalls. Tends to flood the passages and will often clear the crud. Course it's not recommended from a safety standpoint, but nothing that works is recommended these days..........
An old trick if you have junk in the carb orifices is to remove the air cleaner, rev it to between 1500 and 2K rpm and slap a piece of board on the carb top until it stalls. Tends to flood the passages and will often clear the crud. Course it's not recommended from a safety standpoint, but nothing that works is recommended these days..........
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Lead Driver
Joined: Apr 2002
Posts: 8,813
Likes: 13
From: Littleton, New Hampshire
Originally Posted by leonharu
I adjusted in until truck ran rough and vacuum started dropping then I backed out about 1/4 turn on one screw.On the other screw it don't seem to effect the idle and the screw is ran just about all the way in.I don't understand this!
Roast em' if you got 'em
Joined: Mar 2005
Posts: 21,984
Likes: 9,837
From: Rio Rancho, NM
Just a quick note here:
While checking for vacuum leaks using starting fluid, carb cleaner, wd-40, or other flammable materials be a little careful that you don't have some bad plug wires. A misplaced spark can lead to some exciting times in the garage (I'd rather not go into the details on why I'm bringing this up.....eyebrows do grow back though)
Bobby
While checking for vacuum leaks using starting fluid, carb cleaner, wd-40, or other flammable materials be a little careful that you don't have some bad plug wires. A misplaced spark can lead to some exciting times in the garage (I'd rather not go into the details on why I'm bringing this up.....eyebrows do grow back though)
Bobby
Postmaster
Joined: Jun 2004
Posts: 4,190
Likes: 2
From: Riverside, So Cal
Originally Posted by bobbytnm
....(I'd rather not go into the details on why I'm bringing this up.....eyebrows do grow back though)
Bobby
Bobby
Posting Guru
Joined: Jan 2007
Posts: 1,527
Likes: 2
From: Grande Prairie, Alberta
Originally Posted by GreatNorthWoods
If it's running okay with one idle screw all the way in and the other at only 1/4 turn my guess is that it's getting air from some place else (like the base gasket or some other place on the carburetor). Like Tim said the idle mixture screws should be open 1 1/4 to 1 1/2 turns...