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post #1 of (permalink) Old 09-05-2001, 10:15 PM
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carb adjustments

i have the notorious 4.2L engine in my yj and the stock carter carb. any adjustments i can do? does anyone know the stock amount of turns that the idle mixtures screws should be set at? my gas mileage is down there at 9 mpg and the jeep hesitates sometimes like its getting too much gas or not enough. up hills it dogs. i know that this is common but is there anything that i can do to the carb or anything else. i plan to add a weber carb and tfi ignition soon but dont have the money quite yet.

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post #2 of (permalink) Old 09-05-2001, 11:00 PM
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Re: carb adjustments

MotorCraft 2100

Just thank the Jeep gods that it runs.
Your lucky it doesn't stall at every stop sign.

Jeep Icon, Raised 2", Lowered 2", 4pt Independant Suspention. (Yes, that is an Oompa Loompa driving it.)
Infernozx is offline  
post #3 of (permalink) Old 09-06-2001, 07:41 AM
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Re: carb adjustments

Not much to adjust on the stock BBD carb if the computer is still connected. The computer will notice your changes and attempt to correct them. My understanding on the problem is that the computer is working fine but the mechanical controls & sensors wear out and cause incorrect fuel mixture adjustment. Your main two options would be to replace things like the stepper motor (at the rear of the carb), oxygen sensor, vacuum solenoids & switches, etc -or- do the nutter bypass. Replacing parts is expensive while the nutter bypass is free so this might be the way to go while you save up some cash for the webber conversion.
My CJ had some of the same symptoms you describe so I did the nutter bypass. No improvement in performance like some of the articles calim you will get. However, I did get major improvement in dirveability (it would actually idle) and some improvement in mileage. All for about 30 mins of work. BTW - after the bypass it would run slightly better with vac advance connected to ported vac, but I noticed no big change between ported vac and manifold vac. Also 2.5 turns out is a good place to start with the mixture screws. From that point you can adj them in (leaning the mix) to get the best lean idle thingy that is so important.
Also check for correct timing. Also check all vac hoses for leaks, several small leaks equal one big one which means poor performance. Many of the vac hoses can be disconnected after the bypass as their function is deleted. Check for correct vac hose connection as well.
For more info - Check in the ORC tech pages for a good article on making the BBD/258 combo run better, complete with vac diagrams & pics. Also you can do a search on this board or the web to find tons-o-info on the nutter bypass.

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