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Unread 09-28-2008, 03:58 PM   #1
ericleach
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1984 CJ7 
 
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CJ-7 stalls when braking

I have an 84 CJ-7. When I bought it the idle was set high to correct a stalling problem. If I set the idle to factory setting it will stall when the brakes are applied. I'm no mechanic, but I've been able to figure out a few problems by reading the manuals and getting advsie from the internet and I was hoping that someone would be able to help. Everything I find seems to point to a faulty brake booster, but let me know what you think. Thanks for helping out a "mechanic" in training.

Eric.

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Unread 09-28-2008, 04:25 PM   #2
Mike Romain
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Does it stall when you are moving and hit the brakes or when it is stationary?
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Unread 09-28-2008, 05:03 PM   #3
Face
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When mine was doing that it was the factory BBD carb. I threw that thing in a box and installed a Motorcraft carb with no regrets.
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Unread 09-28-2008, 06:11 PM   #4
NH2112
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Take a look at the check valve on the booster and the vacuum line running to it from the carb.
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Unread 09-28-2008, 06:26 PM   #5
ericleach
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Only when it moving...it's more prevalent when I'm at higher speeds and braking harder. I've replaced the vacuum line already.
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Unread 09-30-2008, 07:24 AM   #6
Jayson44
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check all your vacuum lines...mine did that for a long time until I found a vacuum leak.

J.
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Unread 09-30-2008, 08:57 AM   #7
Mike Romain
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Quote:
Originally Posted by ericleach View Post
Only when it moving...it's more prevalent when I'm at higher speeds and braking harder. I've replaced the vacuum line already.
OK, that indicates a sticky EGR valve to me.

To test it, just unplug the EGR and block the line, then see what happens. They can be removed and the valve soaked in carb cleaner to get the buildup off sometimes, sometimes they are actually broken, like one of it's braces has rusted off.
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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 10-01-2008, 11:37 PM   #8
LostINohiO
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ok listen:

you have clogged idle jets in your venturi...

the good news:

you can fix this yourself in 20 minutes...

u have to take the air filter off... remove the choke plate rod... remove the choke plate.... unscrew the venturi.... pull it out... try not to mess up the gasket unless u have a spare rebuild kit around...

run carb cleaner and guitar string (i used a "B" string) or piano wire through the idle jets and make sure they are clean clean clean... put it back together and viola!

no more idle problems....

many a person has replaced their carb unecessarily and complained about the BBD w/o ever getting to know a simple simple fix....

try it....

prove me right or wrong....
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Unread 10-02-2008, 08:32 AM   #9
Mike Romain
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Quote:
Originally Posted by LostINohiO View Post
ok listen:

you have clogged idle jets in your venturi...
The thing about plugged idle tubes is they prevent the Jeep from idling.

The OP has no issues at idle, he has stalling issues when he brakes.

To check for plugged up idle pickup tubes, you get the engine running and 'carefully' watch down the carb while you give it a slow shot of gas. If you have two sprays of fuel, you are good to go. If you have drops of gas dripping, you have tube issues.
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89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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Unread 10-02-2008, 08:43 AM   #10
CGrugger
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Mine did this, i fixed it by fixing the timing
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Unread 10-02-2008, 11:57 AM   #11
LostINohiO
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Quote:
Originally Posted by Mike Romain View Post
The thing about plugged idle tubes is they prevent the Jeep from idling.

The OP has no issues at idle, he has stalling issues when he brakes.

i hear what you are saying but mine was doing EXACTLY the same thing and that is how i fixed it...

i never had any problems idling... but when i approached stop signs the jeep would stall...

clean your idle jets...

prove me right or prove me wrong...

even if im wrong u will know your carb better and it will have clean jets! its only a 15-20 minute repair...
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Unread 10-02-2008, 12:00 PM   #12
LostINohiO
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Quote:
Originally Posted by Mike Romain View Post
The thing about plugged idle tubes is they prevent the Jeep from idling.

The OP has no issues at idle, he has stalling issues when he brakes.
he probably has no issues at idle because as he stated the carb has been set to run rich just because of the idle problem... the PO of mine did the same thing....

i just now noticed this was mike romaine... normally i wouldnt question your wisdom at all... i have only been into jeeps for a few months...

but so far he has stated exactly what i was going through a few months back.... the idle jets fixed it... but then he will need to re-adjust his carb.... and set his timing...

may as well go ahead and nutter bypass the thing and be done with it...

$0.02
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Unread 10-02-2008, 12:58 PM   #13
Mike Romain
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Quote:
Originally Posted by LostINohiO View Post
he probably has no issues at idle because as he stated the carb has been set to run rich just because of the idle problem... the PO of mine did the same thing....

i just now noticed this was mike romaine... normally i wouldnt question your wisdom at all... i have only been into jeeps for a few months...

but so far he has stated exactly what i was going through a few months back.... the idle jets fixed it... but then he will need to re-adjust his carb.... and set his timing...

may as well go ahead and nutter bypass the thing and be done with it...

$0.02
I just read that again, and you could easily be right. He should check them at least as I mentioned.

There also may be issues with the charcoal canister purging at idle blowing the vacuum out. That can be tested by tracing the PCV line to the rear of the carb and finding the T fitting there where the line goes tot he charcoal canister. At idle pinch this line off. If the idle changes, the canister purge is bad or plumbed wrong.
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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 10-02-2008, 05:24 PM   #14
LostINohiO
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yep listen for hissing vacuum leaks... check your charcoal can.... clean your idle jets .... set your timing... do a nutter bypass...

rinse, spit.... repeat and brush twice to be sure...
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Unread 10-12-2008, 12:40 PM   #15
rob777
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Vacuum lines may be attached but loose. Don't just look at them, pull off and make sure of each connection is tight and that should do it. I did the venturi thing too, and it helped with rough idle. Couldn't hurt to do.
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