Strange Cold-start Behavior / '83 258 with Feedback BBD

[markindy]

I'm trying to sort some cold-start issues.  When I bought the car it ran fine, but loped at hot idle and the electric choke didn't seem to function at all.  The original carb's barrels were carbon-black and the wire to the choke had been soldered-on.  I bought a cheap Chinese replacement carb as a stop-gap, and a rebuild kit for the Carter. 
The knock-off carb actually works great when the engine is warm, but cold-starts are still strange.  The electric choke and vacuum dashpot seem to work as they should, and the car starts wonderfully for about 1-2 seconds then shakes badly...like it's running on half the cylinders...but will smooth-out after a minute or two.  The connector for the feedback solenoid seemed flimsy, so I installed the original solenoid onto the new carb...but no change.  I'm not sure the feedback system has anything to do with this problem, but thought it was worth a try.  Again...once warm, everything is great.
Since the air-pulse system is useless due to rusted-off connections, I'm thinking about ditching most of the vacuum nonsense and going with a Carter that doesn't have a feedback solenoid.  This would at least preserve the PCV and EGR systems and make me only a mild eco-terrorist.  Anyone have other suggestions or things I should check?

[89 MJ]

I think its worth rebuilding the original carb and see if that fixes it. It seems like with these cheap, Chinese knockoff carbs you either get a good one or a bad one out of the box and no amount of adjusting will fix it.
I suppose you could check for vacuum leaks using a can of brake clean around the base of the carb, but that's all I would try.

[MIPS]

The electric choke and vacuum dashpot seem to work as they should, and the car starts wonderfully for about 1-2 seconds then shakes badly...like it's running on half the cylinders...but will smooth-out after a minute or two.

I have basic emissions as well and mine does this too when it's exceptionally cold out. Put it down to the cylinders and manifold are cold, which is why the manifold has both the electric and coolant heating to get it warmed up as fast as possible.
A cold engine with the feedback requires the initial choke-pull-off to be set almost perfectly. The feedback system is disabled when the coolant and intake air temp is too low. The secondary air system not working will not affect any part of the feedback system. It's all downstream of every sensor in the system. One thing I found is that if the stepper motor isn't cleaned when the carb is rebuild it has the tendency to stick in colder weather. I follow Chrysler's old suggestion for cold starting and to do one pump to load the choke and set it on the fast idle cam, start it and leave it until all cylinders are firing before tapping the gas to unload the fast idle.

The connector for the feedback solenoid seemed flimsy, so I installed the original solenoid onto the new carb...but no change.

The clips that keep the harness snapped into the feedback stepper like to break off and the computer won't tell you when it's become unplugged. I use a stiff piece of solid core welding wire passed through the back of the connector and wrapped around the two bolts that hold the carb together to retain the connector in the socket.

[Trooper]

Here is some info on the BBD carbs...

https://amceaglesden.com/guide/Curing_Carter_BBD_Carb_Issues

[markindy]

Thanks to everyone who provided suggestions for my problem.  As an update, now that the mornings are getting colder in Indiana, I checked the operation of the choke again.  I would swear on a stack of Bibles that the vacuum pull-off of the cheap replacement carb had been working, but when I checked again it wasn't.  The diaphragm is fine...I used a hand-held vacuum pump to pull it back and the choke plate didn't move at all.  I bent the linkage to get the specified 9/32" clearance and things were much better.  The engine, however, still coughs and sputters for 10-15 seconds before smoothing-out.  Maybe the EGR valve?  Again...once warm, everything is fine. 
I'm also not completely sure the choke thermostat is set correctly.  Every spec sheet says to set it one notch rich...but there is no marking on the choke housing.  Even the original choke thermostat had no indicator line.  How do yo know when the thermostat is correctly set?

[MIPS]

Maybe the EGR valve?

If it's closed, it's closed. These are backpressure EGR's so if you take a vacuum pump to it it will just act like it's leaking. You gotta blow and hold pressure into the exhaust port of the EGR and apply vacuum for it to operate. On a cold Eagle there's at least two different vacuum switches that prevent it from operating until the coolant temp and the air cleaner temp is above threshold. If the EGR is opening on a cold fast idle you have a vacuum routing issue.

Every spec sheet says to set it one notch rich...but there is no marking on the choke housing.  Even the original choke thermostat had no indicator line.  How do yo know when the thermostat is correctly set?

I'm looking at my spare carbs and they both have a line scratched on them, but in slightly different locations. The aftermarket electric choke housings don't seem to have a mark or notch either.

Give me a few minutes to read the TSM and test the procedure on a carb and I'll get back to you.

Edited: Ah heck,  I just made it into a video you can work with.

https://www.youtube.com/watch?v=Rxv-SQCmIWo

[markindy]

MIPS - Thanks so much for the link.  I did most of that, but finding the sweet-spot for the electric choke is definitely worth another look.