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Unread 01-09-2016, 11:43 PM   #1
Nemojj
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1989 YJ Wrangler 
 
Join Date: Dec 2015
Location: Mojave, Ca
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Help carburetor 4.2

Does anyone know where you can order a new stepper motor I think it's called the part that the wires plug into on the backside of the carburetor on a 89 Yj 4.2 mine is going bad

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Unread 01-10-2016, 01:52 AM   #2
SailerMatt
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1995 YJ Wrangler 
 
Join Date: Dec 2014
Location: Vallejo, CA
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Look up the nutter bypass. One of the steps is disabling the stepper motor.

Then you won't need to hunt down a replacement!

Then do the team rush upgrade too.


Ok. time for bed.
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Unread 01-10-2016, 06:08 AM   #3
Mike Romain
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Are you sure the stepper motor is going bad? They aren't known to fail often. Maybe it needs lubrication? Their movement depends on ECU input. You can test them by carefully adjusting the mix screws, counting how far you move the screws so you can put them back the same as they were. If you turn the mix screws in forcing the carb lean, the pin you can see should move forward into the carb. If you move the mix screw out making it rich, the pin should move back out of the carb. Ideally they should be centered at idle with 1/8" of shoulder showing before the taper.
I don't know of any suppliers. Maybe national carb that sells replacement carbs might be a source.
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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Unread 01-10-2016, 04:38 PM   #4
dancytron
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1990 YJ Wrangler 
 
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The two needles that the stepper motor moves are attached to a plate via notches. The motor moves the plate.

When I first got my jeep, it was all gummed up with crap and didn't move at all. I took it apart and cleaned/lubbed it and it moved again (but I was already in the process of nuttering it, so I just put it back together and set it in the right spot.)

I'd try taking it apart and cleaning/lubing it up and seeing if that fixes it. Be careful, there is a spring in there that will try to escape.
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Unread 01-10-2016, 08:22 PM   #5
Nemojj
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I live in California I don't think I can do a nutter bypass and it pass smog
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Unread 01-10-2016, 09:34 PM   #6
Drednot
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Yeah, you cant nutter if you have to smog test.

What makes you think it going bad?
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Unread 01-10-2016, 10:01 PM   #7
Nemojj
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Quote:
Originally Posted by Drednot View Post
Yeah, you cant nutter if you have to smog test.

What makes you think it going bad?
When it's at idel it you can hear the motor kinda change idel a lot and the smog guy said that it's because the stepper motor is going out and when I go in reverse sometimes it dies and he said that's a cause of the stepper motor going bad. So I can do a nutter bypass and it still passes smog and I've heard different things about a nutter bypass can you tell me the pluse side of doing it the pros and cons
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Unread 01-11-2016, 07:35 AM   #8
Mike Romain
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Quote:
Originally Posted by Nemojj View Post

When it's at idel it you can hear the motor kinda change idel a lot and the smog guy said that it's because the stepper motor is going out and when I go in reverse sometimes it dies and he said that's a cause of the stepper motor going bad. So I can do a nutter bypass and it still passes smog and I've heard different things about a nutter bypass can you tell me the pluse side of doing it the pros and cons
You are in California. Forget all about the nutter bypass, that is only for places that "only" test tailpipe emissions. Not a hope of that passing there.
You sure could just be describing plugged up idle pickup tubes. That causes rough idle and stalls. The tubes have crimped ends that are too small so they collect junk. We normally oversize them to 0.032". This fixes the issue and was recommended by AMC back in the day.
To see if this is your issue, at idle carefully look down the carb while giving it a slow shot on the throttle. If you see drops of gas coming out, you have issues with the tubes. You should see sprays of gas, no drops.
Here is a link to how fix that.
http://www.jeeptech.com/engine/carter.html
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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Unread 01-11-2016, 08:06 AM   #9
vadslram
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Besides checking and cleaning/oversizing the jets you need to check the O2 sensor. If you are lucky it is only the sensor going bad and not the ECU. The stepper is driven by signals from the ECU based on the relative O2 composition in the exhaust. If the sensor is being erratic then the Ecu/stepper will be constantly searching to get the stoicometric proportions right.
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Unread 01-11-2016, 04:21 PM   #10
SailerMatt
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Sorry about suggesting that, I should've checked your location first.
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