On the I6 258 w/Carter BBD, the Tech bulletin says that in order to set the idle/air mix, the engine s/b warm. The engine should then be shut off and restarted and within 15 seconds, the stepper should be unplugged, which puts it in the initialized (middle) position. Nutter says that in order to by pass the computer, the stepper s/b put in the full rich position. Wouldn't it be better to set the stepper in middle position to bypass the computer? I'm not interested in replacing the Carter yet.
That Nutter bypass has generated so many questions, some parts of it are very confusing and to a lot of people just don't make sense.
I've read it a couple of times, it is confusing, and I'm pretty mechanically inclined. I think John should really do a rewrite. Are you listening
John? Take a look on the old board, there were about a zillion questions concerning this mod. Sorry I couldn't answer your question,
but I felt this needed saying because the mod looks very good in theory.
Brad (from the 4 Wheeling center of the universe, 4 corners USA)
I did the nutter on my 88 yj with 258 and a weber, and I was not impressed with the ignition performance. I only did it to remove the small amount of change that the computer still had on the timing, as I still seemed to need to play with it a lot.
After I did the nutter, the jeep ran great for about 3 weeks, then it starter to skip and run really crappy. Personally, I think that the removal of the computer, the way that the nutter is done, does give you a non-computer controlled spark, but not of the proper duration or something... I don't know.
Go weber and GM HEI, and don't look back.
88YJ,4"susp,33"BFGMTs,9000#winch, hm swing out TC/HL mount ,258,999,4.10,weber32/36,GMHEI.
The stepper motor on the fedback BBD2 carb is only about 10% of the main jet. Where I live at 7,000 feet above sea level, leaving the motor in the lean position works perfectly. I am not sure about sea level. You can probably try it in both positions, and check drivability. If you run into a lean stumble or surge at cruise or on demand power, you may want to try to get it back to the rich position. Another way around it is to move the position of the power valve to a richer position.
People dog these carbs quite a bit, however they have many nice features that most carbs don't have. The accelerator pump is fully adjustable, and the power valve has three adjustments that make fine tuning very easy. The only big drawback to them is the notorious problem of the emulition tubes becoming restricted. This is easily fixed by drilling the botton of the tubes with a .040 or even larger hole.
As far as computer controlled timing is concerned, the computer only retards the timing about 3 or 4 degrees. The easiest way to bypass this is just unplug the 4 and 10 inch vacuum switchs. This is the three wire connector that the data label tells you to disconnect when ign. timing is set. The Motorcraft dist. still has plenty of both vacuum and centrificial advance to maintain a good spark curve. You may want to play with the base timing settings 3 or 4 degrees for optimun preformance.
Remember when you set idle mixture, pull the p.c.v. valve and let it draw fresh air, not vapors from the crankcase. Also disconnect the charcoal canister purge and plug it. This will give you a constant to work with, as both of these devices will change mixture.
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