I think many of you are missing the point. After you turn off the ignition, THERE IS NO SPARK. THEREFORE THE PROBLEM CANNOT HAVE ANYTHING TO DO WITH IGNITION TIMING. There is no spark to light things off.
Karma, you probably do not know this but. TYPING IN CAPS IS YELLING.
TYPING IN BOLD CAPS IS SCREAMING... I am sure that you did not mean it, Now you know.
Sorry guys but each of you mean well but are a little confused.
Yes dieseling is caused by hot spots in the combustion chamber. It can be exacerbated by overly rich mixtures and excessive ignition timing.
Carbs are broken down into various circuits. Each circuit has it`s own function. At closed throttle the throttle plate has only the idle ports in the venturi open. Thus the idle mixture is controlled by the idle mixture screws.
I am not going to go in detail on how each circuit works but suffice to say that each circut has a function and is adjustable.
Daffy`s problem is none of the above. His is a problem with inconsistent idle speed. As he says, "If the idle is back down to 700 rpm it shuts off but at 1200 it diesels".
Daffy, you need to figure out if the throttle return spring is weak. The cable kinked or something is touching the linkage preventing the idle speed from consistently returning to the 700 rpm figure. Fix that then try adjusting the idle mixture for best performance. Which, if you don`t know how there is a plenty of information on the net.
Thanks for all of the helpful replies. Can anyone tell me, how do you adjust fuel/air mixture?
jsawduste- you got it, that's my problem in a nut shell. Maybe it will help you or someone diagnose my problem by telling you this ---> When I got the jeep it wouldn't idle, so I cleaned out the idle tubes, and put them back in (I did NO changes to anything else on the vehicle whatsoever other than clean the tubes and put them back). This marks the exact moment that my YJ started to diesel. I probably should have mentioned this fact earlier cause it seems like good evidence for my problem.
By the way, I found a cracked hose and replaced it, my idle is now down to around 900... Still diesels...
Sorry, I overlooked that fact, it's stock... so the carter bbd carb.
I think 'idle tubes' are the correct term though I may be wrong, they are the tubes in the venturi cluster that jet fuel during idle (they were clogged as I hear the carters commonly are)
Another note: the rich/lean needles are always buried to the inside of the carb when I look down in it, but I have seen them move a bit before so I assume the computer is working I'm just not sure what that means. Just trying to give as much info as I can.
Figure out the nutter by-pass! All of the emissions crap on there is telling the ignition/timing how to burn. if your emissions equipment is not emaculate, or if you have modified anything, it will throw the whole system off. BY-PASS it! you wont regret it.
Search the forum for the nutter in detail. It's pretty easy. You just cut the orange and purple wires that come out of the firewall and go to the distributor then cut the same colored wires leading to the ECM in the fender. You splice in a new set of wires (color to color) from the ecm to the distributor. Oh, yeah, if you twist the spliced length of wire it wil reduce the electrical interference.
some say bypassing emissions is bad, but i garontee it'll run more eco-friendly (burn more efficient) after you by-pass.
bioblitz- Thanks for the suggestion. I actually tried to do the nutter last week and couldn't get it to work and since my jeep is a daily driver so it can't really be out of commission for me, so I got intimidated and rewired to the computer. The reason I couldn't figure it out is because I have an aftermarket Jacobs electronics unit and it doesn't have purple and yellow wires, the wiring looks different with different colors and I couldn't really figure out what goes where.
I would LOVE to do the nutter, but I'll have to take some time to figure out how.