Weird idling issues
Thread Starter
|
New User
Joined: Mar 2021
Posts: 4
Likes: 0
Weird idling issues
I have a 1984 f-150 with a 351w (VIN H). The issue I am facing is when the engine is warmed up, the engine will idle fine. However when I drive it for a short time and then put it in park or neutral, the idle is high, higher some times than other times. When it does this, I can shut the truck off, wait a couple seconds, start it back up, and it'll idle even better than it did when I first started it. Is this a vacuum leak or some sort of electrical issue?? Not sure why it will run fine after shutting it off for a couple seconds. Any thoughts??
Moderator
Joined: Jan 2001
Posts: 56,992
Likes: 2,741
From: Virginia
Not sure what the VIN H is. You could either have the older style duraspark II system with a regular carb, or you could have the EECIV system with the electronic carb and the TFI distributor. Look at your distributor. If you have a vacuum line going to it you have the old style setup. If you do not have a vacuum connection on the distributor, you have the computer setup.
If you have the old style duraspark II setup with the vacuum line, I would pull the aircleaner and spray the pass side of the carb down with wd40. Spray it pretty good. Then after driving it see if it works better. Also when you are on that side of the carb, see if you have a metal line going down to the exhaust manifold. Make sure it's not rusted off. That would cause this problem also.
If you have the old style duraspark II setup with the vacuum line, I would pull the aircleaner and spray the pass side of the carb down with wd40. Spray it pretty good. Then after driving it see if it works better. Also when you are on that side of the carb, see if you have a metal line going down to the exhaust manifold. Make sure it's not rusted off. That would cause this problem also.
Moderator
Joined: Jan 2001
Posts: 56,992
Likes: 2,741
From: Virginia
There is a illustration in this link. You may not have this if you have the computer controlled carb. Chokes - Gary's Garagemahal (the Bullnose bible)
There is a controlled vacuum leak inside the round black piece. It sucks clean air from under the airleaner, through the pipes where it's warmed up by the exhaust manifold, and that warms the choke and makes it open. The choke is tied to the throttle. If the choke is on, the idle will be faster.
There is a controlled vacuum leak inside the round black piece. It sucks clean air from under the airleaner, through the pipes where it's warmed up by the exhaust manifold, and that warms the choke and makes it open. The choke is tied to the throttle. If the choke is on, the idle will be faster.
Thread Starter
|
New User
Joined: Mar 2021
Posts: 4
Likes: 0
I have a 4BBL carburetor and I have an electric choke. Also, my choke has the no-tamper bolts in them so there is no way to adjust it.
One thing that puzzles me and maybe you might be able to explain, why would the engine idle high (even after it has been warmed up) and then return to a normal idle once the truck is off for a couple seconds and then started again?
I appreciate your assistance!
One thing that puzzles me and maybe you might be able to explain, why would the engine idle high (even after it has been warmed up) and then return to a normal idle once the truck is off for a couple seconds and then started again?
I appreciate your assistance!
Moderator
Joined: Jan 2001
Posts: 56,992
Likes: 2,741
From: Virginia
Even though you have a electric choke, ambient air temp also affects it. So when you turn the engine off, the heat from the engine rises up and continues to warm the choke housing, which will continue to make the bi-metal spring inside open the choke.
You can take those no tamper bolts and get rid of them. If they are a type of rivet, you can drill them out, then tap the holes. When you rebuild the carb they have to come out, you can't dip the choke in carb cleaner it will ruin it. The carb kits used to come with self tapping screws to replace the rivets, or whatever you have on there.
If you have a carb that has never been rebuilt, it is long overdue for a rebuild.
You can take those no tamper bolts and get rid of them. If they are a type of rivet, you can drill them out, then tap the holes. When you rebuild the carb they have to come out, you can't dip the choke in carb cleaner it will ruin it. The carb kits used to come with self tapping screws to replace the rivets, or whatever you have on there.
If you have a carb that has never been rebuilt, it is long overdue for a rebuild.
Thread
Thread Starter
Forum
Replies
Last Post
myhoneystruck
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
3
Apr 8, 2007 12:22 AM
