Surging idle?
Thread Starter
|
Mountain Pass
Joined: Sep 2000
Posts: 233
Likes: 0
From: Eagle River, Ak
Surging idle?
My truck was extremely rich, so I decide to adjust the idle mixture screws.
In order to do that, I need it to idle...
I can't get it to idle unless I have the RPM's up around 2000.
Less than that it will surge and finally die.
This presents an issue with timing it too...
I checked teh EGR valve, when I give it vacuum, it doesn't move.
I plan to replace it because I need to pass IM, but would that alone cause surging idle?
I did search, yesterday, which is why I started with the EGR today!
In order to do that, I need it to idle...
I can't get it to idle unless I have the RPM's up around 2000.
Less than that it will surge and finally die.
This presents an issue with timing it too...
I checked teh EGR valve, when I give it vacuum, it doesn't move.
I plan to replace it because I need to pass IM, but would that alone cause surging idle?
I did search, yesterday, which is why I started with the EGR today!
Thread Starter
|
Mountain Pass
Joined: Sep 2000
Posts: 233
Likes: 0
From: Eagle River, Ak
How do I test the circuits that control it? It is controlled by the vacuum line to it right?
So, just check that it is seeing vacuum when it is warmed up?
If it wasn't working, would that cause a surging idle though?
So, just check that it is seeing vacuum when it is warmed up?
If it wasn't working, would that cause a surging idle though?
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
I suspect a vacuum leak. EGR could be one cause of that. Depending on what year and engine you've got, you're most likely going to have a ported vacuum line coming from the carb going to a ported vacuum switch, then a line from that to the EGR valve.
A good ballpark for the idle mixture screws are to turn them all the way in, then back out a turn and a half. I wouldn't be surprised if your idle was set rich because of the vacuum leak. I'd start looking for vacuum leaks around the base of the carburetor and the power break booster if you've got it. Spray some carb cleaner or WD-40 at the suspected area and listen for your idle to go up--there's your leak.
A good ballpark for the idle mixture screws are to turn them all the way in, then back out a turn and a half. I wouldn't be surprised if your idle was set rich because of the vacuum leak. I'd start looking for vacuum leaks around the base of the carburetor and the power break booster if you've got it. Spray some carb cleaner or WD-40 at the suspected area and listen for your idle to go up--there's your leak.
Thread Starter
|
Mountain Pass
Joined: Sep 2000
Posts: 233
Likes: 0
From: Eagle River, Ak
Originally Posted by fmc400
A good ballpark for the idle mixture screws are to turn them all the way in, then back out a turn and a half. I wouldn't be surprised if your idle was set rich because of the vacuum leak. I'd start looking for vacuum leaks around the base of the carburetor and the power break booster if you've got it. Spray some carb cleaner or WD-40 at the suspected area and listen for your idle to go up--there's your leak.
I tried that same trick, but with carb claener, and it made no difference. I will retry with wd-40.
Elder User
Joined: Apr 2005
Posts: 509
Likes: 0
From: UTI student
Wouldn't starting fluid work better? I used the walmart carb cleaner and couldn't tell anything when I thought I had a vacum leak. I had the air filter off when I sprayed it and some mist flew into the carb. Idle went down. Just for the heck of it I sprayed a short burst over the top, not into, the carb and it sucked it in and started to stall the truck. I've used starting fluid since. It may have been the Tech carb cleaner (whatever it was called) but I use starting fluid now. Just my experience.
Thread Starter
|
Mountain Pass
Joined: Sep 2000
Posts: 233
Likes: 0
From: Eagle River, Ak
I replaced the EGR valve and the carb and spacer gaskets.
Still from 1000-2000 rpm. I can't get a steady idle unless I increase it to 2000.
I bought a rebuild kit and will do that next. I will verify float height and al that stuff then.
Any other ideas?
Still from 1000-2000 rpm. I can't get a steady idle unless I increase it to 2000.
I bought a rebuild kit and will do that next. I will verify float height and al that stuff then.
Any other ideas?
Trending Topics
Thread Starter
|
Mountain Pass
Joined: Sep 2000
Posts: 233
Likes: 0
From: Eagle River, Ak
Weird, I have rebuilt these model carbs before with no problem.
This time I must be soing somethign wrong because it insists on overflowing the bowl.
So I swapped my old carb on.
I removed it a few months because I was too inept to get teh choke working right, an hoped this one would work.
Well, the old carb idles ok except the choke is still maladjusted and it seem the throttle sticks.
I will fix those problems I guess.
This time I must be soing somethign wrong because it insists on overflowing the bowl.
So I swapped my old carb on.
I removed it a few months because I was too inept to get teh choke working right, an hoped this one would work.
Well, the old carb idles ok except the choke is still maladjusted and it seem the throttle sticks.
I will fix those problems I guess.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
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
