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Unread 08-12-2011, 08:22 PM   #1
dcook35
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1990 YJ Wrangler 
 
Join Date: Jun 2011
Location: Lees Summit, Missouri
Posts: 13
1990 4.2L TAC System Issue

I have a 1990 YJ with a 4.2L with stock air intake & BBD carb. The vacuum motor for the trap door assembly in the air intake has apparently failed. I started chasing down vac leaks due to high idle not settling down and the engine idiling fast/slow/fast/slow on it's own. When I put vac pump on the vac motor by itself it will not respond unless I assist it by pressing down on the linkage that attaches it to the air inlet door with my finger. I press it in while applying vac with a hand pump and it will not retract until it is almost bottomed all of the way down. Even then it is a partial response. It will not hold vac on its own and immediately returns to the uncompressed position so I am assuming the diaphram is ruptured / torn / hole in it etc.. The other vac motor for the heated air door works normally and will hold vac indefinately. I want to retain the factory setup and am having no luck in locating one of these vacuum motors online through any auto parts store or oem supplier website. Does anyone have any ideas other than local pick & pull? My local P&P does not have any 1990 Wranglers in stock at this time.
According to the OEM parts catalog there is no part number for the vac motor itself. It appears that it is part of the air cleaner assembly which has its own part number. Anyone have one of these for sale due to a carb swap? Any input will be appreciated.

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Unread 08-12-2011, 08:35 PM   #2
dancytron
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1990 YJ Wrangler 
 
Join Date: Jun 2008
Location: st. louis
Posts: 1,273
Have you tried just cleaning and lubricating it with some silicon spray?

It should be the same for any 6 cyl wrangler before 1990 and I am guessing some CJ's and cherokees with a 4.2 before that.

You should be able to get one here. Lots of people change the carbs and put aftermarket air cleaners on.

If it was me, I'd disable it in the open position. It doesn't do anything except prevent gas fumes from getting out of the carb for emissions purposes and they'd never catch it on the visual emissions inspection they do during the safety inspection.
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Unread 08-12-2011, 08:50 PM   #3
dcook35
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1990 YJ Wrangler 
 
Join Date: Jun 2011
Location: Lees Summit, Missouri
Posts: 13
I'm pretty sure the diaphram has a hole in it. I just checked it out again and noticed that I can hear it sucking air when I pump on the mitivac pump. I'm not worried about emissions inspection as we dont have that in my area. I do want to keep it factory correct though for my own reasons and a vacuum leak is a vacuum leak. I dont think there is any way (that I am aware of) to repair one of these vac motors.
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Unread 08-12-2011, 09:26 PM   #4
dancytron
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1990 YJ Wrangler 
 
Join Date: Jun 2008
Location: st. louis
Posts: 1,273
Well, you should be able to find a used one.

Just for your information, if you are in Missouri, they are supposed to do a visual emissions inspection during the every 2 year safety inspection. How good it is varies wildly from shop to shop. They mainly look for the CAT, EGR valve, vapor canister etc, if they look at all, but technically any bypassed emissions equipment could be a fail.
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