What is a throttle actuator? My Haynes manual shows it in the electrical system for my '85 F150 with inline 6. It also shows 2 wires from a carburetor solenoid. What is it? Does someone have a picture of these 2 parts and where they are located?

 

does your truck have functional a/c and a carburetor? If so, it's probably talking about the anti-stall device to raise your idle when a/c is cut on. But, I don't know the terminology.

 

A lot of people disagree on this, so perhaps we'll never know for sure. My theory is that it is an emissions control device: the throttle plates are such that they close completely with your foot off the gas, the purpose of that is to prevent "dieseling", which is when the engine continues to run after you shut off ignition; bad for emissions. The solenoid props open the throttle plates just enough to idle when the ignition is on and retracts when off, shutting plates completely.

 

Your truck is computer controlled. The computer controls the timing and also the idle speed and the fuel mixture at idle and going down the road.

The throttle actuator is a DC motor with a screw that runs in and out, and is how the computer adjusts the idle speed. The carb has a conventional choke, but it only has one step on the fast idle cam. So when the engine is cold, at the very beginning the choke and the fast idle cam set the idle up high. But soon after as the choke opens, it comes off that one fast idle step, and from then on the computer looks at the engine temperature from a temp sensor, and along with other various things going on at the engine, it constantly runs that dc motor back and forth to set the idle speed.

The solenoid on the carb adjusts the fuel mixture. I haven't messed with the single barrel carter like you have, but on my 2150 2bbl, the solenoid adjusted how much air goes into the engine. It constantly "ticks" back there, as the computer looks at the oxygen sensor, and then adjusts the duty cycle of the solenoid to adjust the air/fuel mixture. Your carb should also have a throttle position sensor made onto it also. And you have a MAP sensor too.

 

Man I needed a second cup of coffee this morning! I missed that you had an 85! That was a feature I liked about my feedback carb inline 6 for cold starts. Had a little more adaptability than a regular old carb.

 

Thank you. I also noticed that according to the Haynes manual the throttle actuator and the carburetor solenoid show up in the schematic even on the 1980 F150 that doesn't have a computer. Is this correct?
A little back story. I received this truck free, but was told that it runs rough. When I got it home I noticed quite a bit of the emission system was removed as well as the a/c. After reading a few threads here on the forum I decided to convert to a duraspark system. I'm replacing my carburetor as well. I'm trying to find what I can remove that is no longer necessary now that the feedback carburetor and computer are removed.

 

The older carbs usually did have a solenoid on the throttle stop (not a DC idle control) but I have never seen a older style carb with the fuel control solenoid on it without a computer.

 

I missed 85 also, because I'm old and read whatever I want to read. I have learned to quit arguing with Wallyworld, and accept I read shelf prices wrong. Dave, on older trucks, what is the solenoid for, is it a thing for idle control due to A/C or emissions kinda thing or ? Don't mean to hijack thread, only to learn (another thing I'm not much good at anymore), but I am curious.

 

" Carburetor throttle solenoids and idle stop solenoids are used to reduce idle RPM to prevent engine run-on when ignition key is turned off. They also were used to increase idle RPM when the A/C was turned on to prevent stalling. Dash pots slowed the closure rate when throttle was released quickly. "

 

I read and understand your posting. I have to assume the throttle and idle stop solenoids are located on the carburetor. I recently bought a new carburetor off of Ebay. The seller described it as a Carter type YFA w/ electric choke. The only electric part on the carburetor was the choke. What do these solenoids look like and why can't I buy them at the locale parts store? I purchased the vacuumed advanced distributor and ignition module along with the carburetor so I could have a Duraspark type ignition system. I'm trying to duplicate an earlier discussion of this same conversion process from this forum. Did I buy the wrong carburetor?

 

If you bought a simpler carb, that is what you want. You do not want all that original junk on there, because it's controlled by the computer which you are going to be doing away with. The computer you have now is very close to a fuel injection setup. It looks at all the sensors for throttle position, manifold vacuum (MAP) engine temperature, engine speed, air to fuel ratio (oxygen sensor) and it takes all this info and makes adjustments to the engine. It gets it's rpm info from the TFI distributor, the same distributor used on the EFI engines.

You are getting rid of the distributor, which relies solely on the computer to advance the timing. You are going to install a older distributor that has weights and springs in it to adjust the timing according to rpm, and a vacuum advance can on it to adjust the timing according to engine load. It does not need the computer. So that handles the timing part.

You do not need a electronic type carb with all those doo-dads, there will be nothing there to run them. You will need to hook your choke wire to the "s" terminal of the alternator. Hook your throttle linkage up, and this older carb will have a vacuum port on it that does not have vacuum present at idle. This ported vacuum port is where you will hook your new distributor vacuum line.

You will have to mess with it a little bit, adjusting the mixture, idle speed and timing and the choke. Once you get it running good, all that other junk under the hood can leave.

 

If you have a vacuum gauge, that will really be helpful in setting your carb. They're not expensive and very helpful, I have a harbor fright one that was only like $20 and use it a ton.

 

A thank you to everyone for the help. One thing I did before asking any of you for advise was tp modify the square shaft that comes off the bottom of the distributor. It was 1/4" to long for the new distributor so I shortened it so the distributor would seat correctly. The other concern is that I spent time finding TDC for #1 cylinder on the compression stroke so I could get the distributor orientated correctly according the the Haynes manual. The problem comes when I expect the timing marks to line up and they don't but yet I know I have TDC for the compression stroke. The truck ran poorly when I first brought it home, but it did run without missing. I don't know if the crankshaft pulley has been removed and put back on incorrectly. Is there a better way to assure the TDC on compression stroke? And if the timing marks don't align I'm going to remove the pulley and align it correctly. Unless someone can think of something for me to check first.

 

Timing marks line up to 0 twice, once on exhaust stroke and once again on the compression stroke. You want it lined up on the compression stroke. You could ball up a receipt or paper and lightly stuff it into the #1 plug hole. (don't drop it inside cylinder!)

Then bump the starter until it gets blown out by the compression. Now rotate the crank the final bit to line up to 0 TDC. If you take off the passenger valve cover while you do this, you can verify when the valves are closed--compression stroke.

 

You can also hold your thumb over the sparkplug hole and turn the engine by hand till it tries to blow your thumb off the hole, and then keep turning it till you hit the marks. Same theory as the paper.

P.S. If you are setting the timing with the computer control type distributor, you need to disconnect the spout connector to take control away from the computer. Then you set it according to the sticker on the radiator and then plug the spout connector back in place.