My 1986 f150 runs super for the most part. Once in a while, after about ten minutes of driving it starts to run real rough and will stay that way as long as i keep driving it. if i pull over and shut it off and let it sit for a few minutes it will be fine again. The last couple of times though it had a hard time starting as though it was flooded, but once the plugs got cleared up after a few seconds it was fine again. I'm not sure but i think it only has a tendency to do this when it a little warmer out. i also notice that it wants to idle high and i have to kick it down every time i stop. Any suggestions, this is really the only trouble that it gives me and it would be great to clear it up....thanks

 

Since you've got rough running and a fast idle, I'd guess that your choke is hanging up and not releasing completely. The next time it does it, take off the air cleaner and see if the butterfly is restricting your air intake. You might have a problem with the choke. I hope this helps.

'81 derful flareside

 

i thought 86's had fuel injection. if so, check the idle air control first , then the fuel delivery system for loose connections if iac is not the problem.

 

Its got the 1bbl carb. i think EFI came out in 1987 for the f150 I6. i will look into that choke situation? What is the best way to free up the choke?

 

Personally, I think the best way to free up a stuck choke is to get rid of the automatic controls and install a manual choke cable. I've had nothing but problems with about every automatic choke I've ever owned or driven. NEVER had a problem with ANY manual choke vehicle. The auto choke on my 84 sticks at the drop of a hat and I've gotten very good at propping it open with a screwdriver that stays on my dash while I start it up. It's on the chopping block this year. I like controlling my choke ... and since you can just push it open with a ****, it never sticks. Good luck!

Chris in Canada ... not bitter about auto chokes much. :P
74 Gran Torino Brougham ... 351W 2v/C6 ... the toy
84 F150 2WD 300I6/NP435 non-OD 4spd/3.08 open rear ... the driver

 

My experience with the problem you have was due to
"dirty linkage" causing the engine to idle faster than what it was set for. I sprayed some Gumout carb cleaner spray on the linkage behind the carb. It wasn't enough to just spray it in one position either. I opened the carb wide-open manually with the linkage and sprayed it down in that position also. You want the outside of your carb clean from any dirt or oily deposits. Use an old toothbrush, spray the cleaner, and scrub 'er down!
This cleared up my hanging fast idle problem in a hurry 100%.

You could also have a choke that has loosened up and slipped into the "Richer" position causing it to choke a warm engine. Check your choke setting on a warm engine....the butterfly flap should be straight up and down.

Has your gas mileage decreased? Black smoke or black carbon soot coming from tailpipe? All signs of over richness.

good luck...keep us updated.



1981 F-150 2WD STYLESIDE P/U
4.9L 1 BBL CARB
C6 AUTO
2.73:1 LIMITED SLIP REAR AXLE
STABILIZER BARS FRONT & REAR
6100 LB GVWR PACKAGE
ORIGINAL OWNER
193,000 PLUS MILES
100% STOCK & UNREBUILT
BUILT FORD TOUGH!!!

 

I had this same problem on an '85, which I believe has the same electric choke setup. If you lose either the direct wire from the alternator to the choke, or the heater element dies, your choke stays shut much longer and then only partially opens. That may or may not be it, as these are an electronically controlled carb, but it did the job for me.

 

thanks for all the responses, i wont get a chance to take it apart until this weekend but i will let youo know how it goes. also last night i took the air clear off when the engine was warm and i did notice that it was not all the way open so i know i have a problem with it. also in notice some metal tubing that almost looked like a gas line coming from th choke, it went down towards the fire wall and ends up near the exhuast manifold, at that point it stops and it not connected to any thing, its just hanging there. any idea on what this might be and shpould there be a fitting on the other end coneecting it to something? thanks again.

 

The tube you are talking about is called the choke heater tube. It probably has white fabric insulation on it. It is supposed to draw heated exhaust air to the choke so the bimetallic spring will expand and open the choke once the engine warms up. This spring is located behind the black plastic choke cover. Your automatic choke will not work properly because the heater tube has separated from the threaded port in your exhaust manifold. My '85 had the same thing occur. I replaced my automatic choke with a manual one available at any NAPA parts store. Like others have said, automatic chokes are nothing but problems. To install the manual choke, you have to carefully pop off the rivets that secure the choke cover plate. You will not have enough room to get a drill in there. If you have a dremel that might work. I used a sharp chisel but busted off part of the casting on the carb. You want to be a little more careful than I was. You can then use self-tapping screws, or tap the holes with 10-24 threads where the rivets were because you have to reattach that choke cover once you install the hardware from the choke kit onto the shaft. I ran the cable for the choke through the big rubber grommet that has a thick bundled wiring harness going thru the fire wall. You need to use some ingenuity when attaching the choke cable bracket support, because it is going to interfere with your air cleaner housing. I installed mine on a heavy bracket attached to the rocker cover to the right of the carb (looking into the engine bay) - this bracket holds the throttle cable or some linkeage. I had to tap holes to secure the choke cable support to this bracket. Then the air cleaner would not fit so I had to bend the cable bracket to almost 90 degrees til it cleared. Do whatever you have to, but trust me, you need to get rid of your automatic choke and install a manual one. To start the engine with a manual choke, push gas pedal down half - 3/4 way, pull out choke all the way, release gas pedal, start engine. Once it kicks over, play with the choke setting til engine runs well, when it's fully warm, push it in all the way.
My truck runs much better with a manual choke.

You also might want to check out your heated air intake vacuum motor - when engine is cold, vacuum should pull the air diverter up which draws heated air off the manifold. Mine was bad and this can really cause problems when driving in cold temperatures. Those feedback carbs won't run right without heating the air before it gets to the air cleaner, and moisture can even freeze in a carb above 32F due to the carb's venturi effect.

Lastly, make sure your EGR is not leaking - I replaced mine once it started screaming (air whistling past the actuating shaft, a real attention getter.)

 

FYI - You can also buy replacement choke heater tube kits from just about any parts store. Sounds like they're about as much if not less work to install as it takes to convert to a manual. Mine was in the exact same condition yours is back in '91 or so and the aftermarket kit is still working like a champ for me. Besides, its back to the way it was designed. All I do to start it is tap the throttle once to get it on the fast idle cam/shut the choke and it cranks over first time every time.

'84 F150
YFA F/B
SROD
"Ex" => Bone Stock

 

[font size="1" color="#FF0000"]LAST EDITED ON 15-Mar-01 AT 02:26 PM (EST)[/font][p]OK- did not know you can get a choke heater pipe, but would have had a hard time getting that fitting off my exhaust manifold. Did you have to remove that fitting to install your new choke heater tube?

 

The heater tube kit I got came with a fitting that goes into the exhaust manifold. You have to drill out the opening in the manifold with a certain size bit that is called out in the instructions. Then you tap the new fitting into this hole. It is just a friction fit deal. Then you replace the old tube with the new one supplied in the kit. I can't remember if you have to flare the end of the tube where it screws into the choke housing or not but the other end just slips into new fitting you just installed into the exh manifold. Mine even came with a new cloth insulation jacketing for the tube to minimize heat transfer to anything that touches it. If I remember right, I got the kit from NAPA in Florida but I've seen them at all different parts stores. Good luck. Let me know how it goes and if you have any more questions.

Will

'84 F150
YFA F/B
SROD
"Ex" => Bone Stock

 

WOW....I'm glad to hear that you can get a replacement tube, the manual choke seem like a good idea, but a lot of work. I'm going to try all the local parts stores around here, (southern NH), until i can find a tube like that. Do you just drill any where that tube will fit in the exhuast manifold or is there a certain spot it has to be in. i tried to find where the original screwed in but i did'nt have any luck although you i really didnt have much time to do a good search. i imagine it went in around where the tubing now just kind of hangs there. i still plan on spraying the carb down well with carb cleaner just to make sure nothing is sticking there either. I wonder if i'll notice any better milage once this new tubing is hooked up. the funny thing is yesterday when i got home from work the truck seemed to be running well so i popped off the air cleaner and the choke was wide open. it ran great again tody although it seems to be idleing a little high....thanks again for the help..this is the first carbuerator I've owned so it comes in real handy

 

You just drill out the hole in the exh manifold that the old tube went into with the size drill bit the kit calls for. It is in the vicinity of where the old one is probably hanging now. It is behind and below the carb. You have to sort of climb up on a stool and look down with the air cleaner removed to see it. If the weather has been warmer there like it has here, that may be assisting the choke to open up like it is now. Let me know how it turns out.

Will

'84 F150
YFA F/B
SROD
"Ex" => Bone Stock

 

The parts store in my town did'nt have one the replaced the original tube, but they had a universal one made by HELP! products. I know what how cheap those universal things can be but this did'nt look too bad so i bought it. it was only $7 any way. turns out the fitting they supplied wont' work and I did'nt have any extra fittngs around to try so its a project that will get put off until next weekend. this universal thing did'nt require me to drill at all, it just had a heat shroud that gets clamped around the exhaust manifold with the tube sticking out of it the goes to the choke. it sounds like this application is to cheap and i think i should check some more parts store to see if i can find something more specific to my truck. has any one used this cheap kind? thanks agian