That worked and we see the picture.
I take it the truck does not have AC as I think I see "Hi Output" on the heater box?
Being no AC and you don't see any plugs to plug the 2 "things" into so as a test to see if they are the cause unbolt both of them from the carb and see what that does.
Do not throw them away you may need them when the idle is back to normal.


Ok, on the throttle cable I wanted you to remove/pop it off from the carb. We have seen the cable hold the throttle open even when everything looks good. The only way to know is to pop it off.
If that is the case most of the time it is the bracket it is bolted to that needs to be adjusted (bent).


Last thing is to recheck the fast idle cam. with the cable popped off, the 2 "things" removed from the carb the last thing I think it could be is the choke fast idle cam.


If all that checks out ok and none of the idle screws are touching the stops then it has to be in the carb. Bent throttle plate or an internal leak.

Well I keep thinking of things....vacuum leak. Using carb cleaner with the little hose, motor running, spray along the head & intake manifold then around the base of the carb to see if that does anything to the RPM.
Dave ----

 

Can not tell from the picture but those two connectors don't happen to mate up, do they?

 

If they both plug together how do they get power?
Dave ----

 

They don't plug together, they are both male ends. I don't see any open wire connectors where they could plug in. I wonder what would happen if I started the truck, let it warm up and just put 12 volts to those two wires?

 

one does look like a dash-pot? (on left)

 

The idle stop screw not touching is going to be most of your problem. That is a sign the engine is getting uncontrolled air and fuel from somewhere. That along with the fast idle is sucking too much fuel into the engine when the ignition is cut off, and there is a hot spot in the exhaust that is lighting off this extra fuel.

Since this engine has been swapped in, the carb may have come with the engine, and who knows what year all this is. During I believe 1984 and after, it would be a electronic setup for these engines. Someone with more knowledge may be able to look at that carb and tell if it's the electronic model.

But even if it's the electronic model, it should not have the problem it has. It's going to take some experimentation and taking stuff apart. But once you get it so it idles down slow and you can actually adjust the idle mixture screw and it has some affect on the idle, your problem is going to go away. Right now I bet it's idling so fast, you are idling on the main venturi circuit in the carb, not the idle circuit.

 

As stated above, the engine in the truck now is the 3rd one that it's had. My Dad rebuilt an unknown engine for #2 and I do believe that he re-built the original and had it ready for #3. I do know that he went completely through it, valve job, oil pump, distributor, water pump, etc. He even had it bored out .010 and put oversize pistons in it. He then put the engine in a corner in the garage until it was needed, which happened in the summer of 2014. I have no idea if the carb is original or not, I wouldn't think so with that many miles on it.

 

With the solenoid built in like (franklin?) posted.
I still say undo the throttle cable and the 2 things with the wires and see if it will idle down.


Also I see a green tag on the carb post up the numbers as I am sure someone can find what it came from or is to.
Dave ----

 

So most likely the carb was original to the donor engine, but not your present chassis. For all we know, the donor engine/carb may have come out of a car, not a truck. If so, I think cars had somewhat tougher emissions standards than trucks, so your existing carb may have doohickies never used on trucks.

It may get interesting if you try operating without those extras, regardless of the carb's original. Unless it had been rejetted or otherwise modified, the present carb would have been calibrated to work with those extra components. For example, you may never be able to tweak the idle mixture enough to compensate for the rich mixture you seem to presently be getting during deceleration, and still have it idle okay under other circumstances.

If you haven't seen it, there's another current thread with lots of good info about some of these doodads:

https://www.ford-trucks.com/forums/1...riat-85-a.html


Dave has suggested some things to look for as you try adjusting your carb. Unfortunately, you may hit the limits of possible adjustments because that poor, lost carb is all alone out there in the wilderness, totally unaware some important functions have been disabled.

You might try poking around RockAuto.com for similar years and models, and see if your present carb matches anything. Also look at what they list for your 1980 chassis and see how it compares to what you have. If worse comes to worse, ordering the correct carb for your chassis may be the easiest fix.

 

I believe you. And there are many different causes for a high idle like you are having, but don't get side tracked I think that is the root of your problem.

Someone mentioned it may be the wrong carb

Someone mentioned something is disconnected

There could be a vacuum leak somewhere

Your EGR valve may be leaking.

You may need to investigate your throttle linkage some more

You may need to look at the choke linkage and make sure the throttle is not sitting on a fast idle cam step.

Pull the carb off and make sure the gaskets are good underneath

With it fast idling like that, you can't even adjust the idle mixture properly. You can try it and see what I mean. You can turn the screw in and out and it probably has little to no affect.

 

Dan, not to side track you on the high idle ,but the back firing your having sounds like the same problem I had years back .I disconnected the air pump on my 85 and at times had a back fire that was rifle(scary) loud. I put the belt back on the pump and it went away. Rowdy redneck mentioned this earlier. My truck then had the feedback - carter -1 bbl carb. Good luck TR

 

Here is a close up of the tag on the carb on my truck. I believe that this carb doesn't belong on this truck as I haven't been able to find it on the Internet when searching for 1980 F-150 300 in-line 6. As far as I can find, there should be nothing electric on the carb on my truck other than the choke. <br/>