Join Date: Apr 2002
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Re: Carb Help for an 86 CJ7 with a 258
Well, the PO did *partially* bypass the computer. Because one of the things the computer does control is the stepper motor.
The purpose behind the stepper motor is to enrichen or lean out the mixture depending on the inputs from the various sensors.
Generally, on a stepper motor equipped Carter BBD, when you do the nutter bypass, it runs rich at idle because the stepper motor is placed into the full rich position.
However, if the Carter that it on there now is lacking a steppr motor as you say it is, that point is nil and void.
The two mixture screws on the front of the carb affect idle mixture only (to the best of my knowledge. You turn them in (clockwise) to make the mixture more lean, and out (counter clockwise) to enrichen the mixture.
Personally, my mixture screws ar about 5 3/4 turns out and is set exactly right (measured on a wide band O2 machine at a local shop).
There is another good way to set it though: Back them out a good amount, then slowly turn them in until the engine starts to run rough. Then turn them back out 1/4 to 1/2 turn and this is generally sufficient.