Idles high, why?
Thread Starter
|
Senior User
Joined: Jul 2015
Posts: 106
Likes: 0
Idles high, why?
My 79 2wd has a rebuilt 2150 motorcraft carb. Starts up first turn of the key, warm or cold, drives really nice, no flat spots but it idles really high. If I stop the truck, leave in gear with engine running and take my foot off the brake, the truck will drive forward, not a little, a lot ! Even after the engine is hot, its runs fast. Same in reverse.
I checked the curb idle screw and its almost out so thats not it, I need to check the fast idle setting per other posts in the forum but want to get advise on what could cause it to run fast when warm?
I checked the curb idle screw and its almost out so thats not it, I need to check the fast idle setting per other posts in the forum but want to get advise on what could cause it to run fast when warm?
More Turbo
Joined: Apr 2007
Posts: 656
Likes: 5
From: Salisbury, PA
I am familiar only with Holley's but what comes to mind is to check how far open the primary butterflies are at idle. You may have some adjustments wrong that will not let them close the whole way. Possibly electric choke connection adjustment?
Senior User
Joined: Oct 2013
Posts: 328
Likes: 2
From: Jordan Station, ON
+1 on this... Also, on my carb I have an electronically controlled diaphragm that's designed to reduce the amount of wear caused by the butterfly when it's closing by making it close slower. When I have that hooked up, it doesn't close all the way and the butterfly stays open all the time, causing high idle, so I don't use it.
Thread Starter
|
Senior User
Joined: Jul 2015
Posts: 106
Likes: 0
Yup, I will start with fast idle but before I adjust, which direction is rich and which is lean? The choke housing doesnt have a mark so I assume perpendicular is middle?
I dont think the fast idle is dropping through the cam as expected so I'll set tomorrow am when cold and then follow the steps per manuals etc.
I dont think the fast idle is dropping through the cam as expected so I'll set tomorrow am when cold and then follow the steps per manuals etc.
Senior User
Joined: Oct 2013
Posts: 328
Likes: 2
From: Jordan Station, ON
Trending Topics
Thread Starter
|
Senior User
Joined: Jul 2015
Posts: 106
Likes: 0
I think its the other way assuming you face the carb from the right side of the truck (also based on a 2150 carb pdf doc I found)
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
Thread Starter
|
Senior User
Joined: Jul 2015
Posts: 106
Likes: 0
Ok so I started the truck this am no issues, got it up to temp and pumped the throttle, no change, then I forced the fast idle cam to the next level and the revs dropped to where it should be. Killed the engine and tried to figure out why, never adjusted anything now it wont start. Give it an hour to cool down and will try again but why wont the cam drop when the accelateror is pumped?
I have 2 service manuals open, plus multiple forum posts and im bloody dumbfounded.
I have 2 service manuals open, plus multiple forum posts and im bloody dumbfounded.
Senior User
Joined: Oct 2013
Posts: 328
Likes: 2
From: Jordan Station, ON
Oh, sorry... I'm thinking of my 1bbl YFA from facing forward (behind the carb)
Thread Starter
|
Senior User
Joined: Jul 2015
Posts: 106
Likes: 0
No worries, confirmed with a post by fmc400 on here.
Finally I find out whats happening, engine hot and running, its on fast idle and I pump the accelerator but the lever doesnt hit the cam to move to the next level so the revs drop. If I manually force the cam it drops. If I then pump the accelerator it resets to high fast idle again.
I see it but no idea how to fix it.
Update, some screw (kickdown screw?)between the choke and the carb, so I tweaked it and when pumped the gas, it stayed on idle. Yippee. Now to wait till it all cools and see if it sits on the cam high and then when warm pump da gas, see what gives
Finally I find out whats happening, engine hot and running, its on fast idle and I pump the accelerator but the lever doesnt hit the cam to move to the next level so the revs drop. If I manually force the cam it drops. If I then pump the accelerator it resets to high fast idle again.
I see it but no idea how to fix it.
Update, some screw (kickdown screw?)between the choke and the carb, so I tweaked it and when pumped the gas, it stayed on idle. Yippee. Now to wait till it all cools and see if it sits on the cam high and then when warm pump da gas, see what gives
Thread
Thread Starter
Forum
Replies
Last Post
can0fspam
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
3
Jan 27, 2018 11:14 AM
Billy Brethren
Ford Inline Six, 200, 250, 4.9L / 300
24
Aug 26, 2007 11:34 PM
Plain Old Dave
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
10
Nov 22, 2005 01:15 AM