Intro and 1990 Jeep yj 4.2L Acceleration issues

[murray195]

Hello all,
Unfortunately my first post is a troubleshooting request... but heres some info on my machine:
1990 Jeep Wrangler
4.2L
Automatic
4" Rough country
17" mud and snow tires
Nutter bypass mod
Soon to be installed 3" body lift

I have used the search function on your site, google, and various other 4wd sites.

And here's the issue I'm having:
It idles great, revs up great, but upon accelerating I experience a serious hesitation almost like it's missing.  If i really put my foot into it, it corrects itself momentarily and once the tranny kicks back down it happens again. My vacuum advance seems to be working properly at a stand still (i can see it working). I have changed the cap, rotor, plugs, plug wires, and fuel filter. I just want to get it running properly until I have time to install my MC2100. I'm not sure if it's related or not, but under heavy acceleration, my 4wd light goes out until the the rpm comes back down. I would assume this is vacuum or ignition related but i've gone through my vacuum lines and the ignition related stuff is replaced or bypassed. Any help would be greatly appreciated!

Thanks,
Murray

[AMCJeep]

Tighten up all the intake manifold bolts. After you have done that you will need to make sure the accelerator pump is shooting out properly at part throttle. If it's hesitating at part throttle, you need more fuel to be shot in. Just adjust it to provide more fuel earlier and more volume. The BBD can be finicky but it's very easy to learn and work with. I've made Franken Carbs from BBDs that perform on par with the MC2100 off road and on.

Either way, You are going to love your MC2100 when you do it.

[BlackYJ]

Soon to be installed 3" body lift

Why?  I would not waste your time.  A 1" BL is a good mod, but 3" is excessive and not necessary, plus looks goofy.  A 1" shackle lift plus a 1" BL would be a far better mod.

[murray195]

Tighten up all the intake manifold bolts. After you have done that you will need to make sure the accelerator pump is shooting out properly at part throttle. If it's hesitating at part throttle, you need more fuel to be shot in. Just adjust it to provide more fuel earlier and more volume. The BBD can be finicky but it's very easy to learn and work with. I've made Franken Carbs from BBDs that perform on par with the MC2100 off road and on.

Either way, You are going to love your MC2100 when you do it.

Thank-you for the reply. I managed to get some time at work to tinker with the jeep. All intake manifold bolts seem to be nice and snug... snug is tight, tight is broke right haha? Can you give me an idea of where abouts the two adjustment screws should be set at at the base of the carb(ie 1.5 turns from fully in?). And how much should the accelerator pump move out? I'm really looking forward to swapping in my MC2100.

Why?  I would not waste your time.  A 1" BL is a good mod, but 3" is excessive and not necessary, plus looks goofy.  A 1" shackle lift plus a 1" BL would be a far better mod.

I happen to have a 3" body lift so why not? It's going to give me room to go to 35's without clearance issues. I'm trying to avoid any additional suspension mods until I can afford an eliminator kit. With a nice set of gap guards, I don't think it'll look too bad.

[murray195]

Doesn't it look like a bit of a low rider at the moment?