Sporadically Running Like Crap When Cold?

So when I have been starting the Jeep to let it warm up (its been like 30-45 degrees when I do) Sometimes its idles perfectly and other times it will run like crap and stumble until it gets warm. The idle will be too low like it is starving for fuel and when i give it a little juice it stumbles and really doesnt like it. What’s tripping me up is how sporadically it happens. I was thinking the choke but wouldn’t that be all the time if that was the case? Now I have just started daily driving it this winter so im not sure how it would perform when its warm outside. 258 with a motorcraft 2 barrel carb

 

Automatic choke spring hanging up? Next time it gives you issues, take off the air cleaner and take a look.

 

Carb icing?

Look into the carb throat next time it happens. Humid air near freezing can make ice in the venturi.

Is the manifold heater/stove thermostat arrangement working?

 

Probably contaminated gasoline.

 

This. Try a can of Seafoam in the tank.

 

What kind of choke arrangement do you have on the Motorcraft carb? In California weather, you should be able to pump the gas a couple times and it will start, with or without a choke. It may not stay running if you try to drive, but you should have no trouble starting it and letting it warm up, even with no choke. Maybe it's set up too lean, or has a vacuum leak?

The 21xx can be converted to a manual choke easily using the Dorman kit, if you are willing to pull a cable to start. The original choke is thermoelectric, meaning it needs both a supply of hot air and an electrical connection to the ignition. Won't work right without both connections. Supposedly you can use the thermal chocke cover from a '77 or later Carter BBD, flip the element over to reverse the rotation, and have a 100% thermal choke. This requires a hot air stove, which on the 1V 258 is just a pocket that the hot air tube slips into. Again, there is a replacement hot air stove available from Dorman that clamps on to the exhaust manifold, if you can't get the stove for the original YF to work.

I tried the flipped-over BBD choke cover on my 258, and went back to the manual choke. Anoterh option - you can probably use the Holley electric choke kit for the Holley carburetors on the 21xx. I have not tried it, but I have mixed and matched choke linkage parts between Holley and Motorcraft carbs and I strongly suspect it would work. This would still need an ignition wire, and typically it also uses an oil pressure switch so that the choke opens only when the engine is running.

 

It started up and ran perfectly fine this morning in about 60 degree weather. I have about half a tank of less than a week old gas in it. How difficult is it to switch to a manuel choke?

 

Easy. Dorman Products - 55101

The conversion does not work exactly like an OEM manual choke. At a cold start, you have to open the throttle to set the choke, but once you do that, it all works fine. Just don't forget to close the choke when up to temperature.

 

Just a comment - the piece they give you in that kit to anchor the end of the cable is very flimsy - I did not use it. Instead I made a bracket from some 1" x 1/8" steel from the home center, and used that.

 

Contaminated with water, and resulting in fuel line freezing? Highly doubtful unless poster is fortunate enough to not use ethanol blends.

If the ethanol in the blend has gone stale and allowed water separated out I'm not sure seafoam will improve anything. Adding HEET (more ethanol) is probably not much of a solution, either.

Seafoam is great for varnish contamination but that wouldnt be temperature sensitive.

I'll go with choke slipping off the linkage notch.