Stalling When Put Into Gear

[ilovefords31]

I have a 1986 F-150 2wd with a 4.9 automatic c6 transmission, and the feedback carb system. For the past several months I am having rough idle issues when the truck is starting cold, or cooled down. When I put the truck into reverse, or drive for the first time after cold starts, it wants to stall. Then once I move the truck, and get it going, it doesn't do it again until it is cold again. I have replaced many, many things. The only things I have not changed are the components that go to the air pump, smog system. I Changed the transmission fluid and filter about a year ago, and adjusted the band at the same time. I am not sure if it is a transmission problem, or a fuel problem, but the truck does not have a high idle when it is cold, and I cannot get it to idle high. I really need help. I am really stuck, and there are absolutely NO garages in this area that work on older vehicles. Especially the feedback systems. I have a code 41 also which is lean condition.

 

[fatherdoug]

Most shops put their fingers in the form of a cross when you ask them about feedback carburetors. Did you replace/adjust the antistall dashpot? This would cause a stall condition when cold. Other times it would not be a problem.

 

[ilovefords31]

Fatherdoug please don't think I'm dumb but is that the solenoid that moves the throttle when it is about to stall, that is mounted on the carb behind the throttle? If so, then no I did not replace that and I am not sure if it works, or how to test it. Rock auto has it listed as a idle air control heres the pic of it

 

[fatherdoug]

The part I was thinking about is a choke pulloff or antistall dashpot, which controls how fast the choke opens up when the engine is started. There is an adjustment screw on the backside of the pulloff to change the response. If the choke opens up too fast, then the engine could stall. I don't remember which way is which on the adjustment screw.

Find the carburetor section for your truck on Rockauto, then select "choke pulloff".

 

[ilovefords31]

My choke pull off is only a year old. I bought a rebuilt carb from national carburetors about a year ago, and it was part of it. But I don't know if mine is adjustable. I know that there is no screw on it. The only possibility would be to bend the arm connected from it to the choke. My choke has a heat riser, and bimetallic spring on it. The bimetallic spring heats up from electric heat, and engine heat. The pull off opens the choke a little bit, and it runs o.k. in the morning, not perfect but o.k. it is when I let it sit for a couple hours that this happens. To me, it does seem like a choke issue, but I have tried every adjustment I can find on this thing. I moved the bimetallic spring housing, to move the choke all kinds of different ways, and I've adjusted the idle mixture screw, which is at 7 turns out which I know is wayyyy to far, but it rough idles horrible if it is less than that. The pull off opens the choke about 1/3 open. I don't know if that is too much or what, but I know if I put my hand over just half of the carb throat to choke it out, the idle becomes way more stable. I cannot find any vacuum leaks anywhere, but I changed as many vacuum hoses as I could. The only ones not changed are the plastic ones that go to the 3 vacuum valves located by the firewall on the valve cover, because I cannot find new ones.

 

[fatherdoug]

After looking at a pull off for your make/model, it looks like there is no adjustment screw. I apologize. I'm used to dealing with older models. But, if I understand you correctly, the choke is 1/3 open when starting the truck? If that is the case, then the choke is too far open. Putting your hand over the top of the carburetor performs the same function as the pull off . The choke should be almost all the way closed when the vehicle is started.

 

[Beach66Bum]

Yes, your right Doug. 1/3 open is to much. For the setting on the choke plate when cold, it should not be open more than a paper clip diameter. (like an 1/8th inch)

The dash pot was an emissions device. It helped prevent excess unburnt gas when the throttle plate quickly changed from open to closed, ie. accelerating in your vehicle, then coming to a stop. On automatic transmissions it also prevented possible stalling by preventing flooding of the carb. They were also on manuals, but you could eliminate them without any issues.

The choke pull off runs of vacuum. It's purpose is to open the closed choke plate just enough to allow cold start up. It is directly tied to the proper adjustment of the choke.

Ford had 3 types of systems for the choke control.
Heat riser tube off the manifold only.
Heat riser tube With electric assit.
Electric only.

 

[ilovefords31]

So if it can be eliminated, then I will unhook the vacuum line and see if that makes any difference. I will let you guys know what happens. Thanks to you both for your replies by the way. I have been on other ford truck forums and there is nobody that post any answers except this one guy who tries. But I really appreciate your help.

 

[ilovefords31]

B.T.W Doug.... Love that truck in your profile pic!

 

[Beach66Bum]

So if it can be eliminated, then I will unhook the vacuum line and see if that makes any difference. I will let you guys know what happens. Thanks to you both for your replies by the way. I have been on other ford truck forums and there is nobody that post any answers except this one guy who tries. But I really appreciate your help.

On the manual transmissions, yes. Not 100% sure if you can on the auto's. There will be more guys to answer later this evening

I have some pic's in my gallery of a 2150 carb (factory Ford) and the adjustment screws and such. At work now but will post a few for you later.

 

[ilovefords31]

Awesome, thanks Amkatt. I probably have to adjust it by bending the rod that links it to the choke. It is bent, which seems unnecessary to me, so I was thinking it might be an adjustment. Otherwise why would the link not be just straight?

 

[fatherdoug]

B.T.W Doug.... Love that truck in your profile pic!

Thank you!

 

[ilovefords31]

I tried taking the dashpot out of the equation, but it just died. I took off the IAC and adjusted the stop screw 3/4 of a turn, and the idle is up a little. I won't really know if it fixed it until morning when it is cold again, but I will keep you guys informed. The little anti dust grommet was missing for some reason on the IAC, but I am pretty sure it is working. Thanks again guys.

 

[ilovefords31]

Just as a side not though.... with the anti stall dashpot.... I closed the choke plate a little bit, I mean really little bit, and the idle straightened out great. I went a little further and it roughened up. But there is no adjustment so I don't know what I could do to change it.

 

[Fellro]

The choke needs to be closed for start up, then pull open a bit once started. Once warm, it should be straight up and down. You can run an old carb with no choke at all, just isn't a lot of fun... I am not overly familiar with the Ford electronic carbs, so I'm not going to say a whole lot... I wasn't outright aware that the IAC was on carbs as well. The IAC does control the idle as well through the amount of air it lets through past the throttle plate.

 

[ilovefords31]

Fellro that is what the carb is doing, so I guess it is correct. The IAC is something that when I replaced the carb it did not come with a new one. I fealt it moving the throttle when the engine was starting to stall. The truck runs really good once warmed up, it just does not seem to have any idle control. Like going down hills you can hear the backfiring as if it is out of time, but I timed it exact 10 deg btdc. I also did a full tune up including fuel pump and filters. I even bought the better coil the accel. I am beginning to think I just don't have things tuned correctly for the feedback system.

 

[ilovefords31]

Well, I adjusted the IAC about 3/4 of a turn out and it is idleing great, and it's no longer stalling when I put it into gear. It seems that the new carb had to be adjusted to my engine. Thanks to you all for the great help, and god bless!

 

[Beach66Bum]

Great to hear