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Author
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Topic: vacuum leak?
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craigber
Journeyman Posts: 78
From: Vancouver, Canada
Registered: Sep 2000
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posted 06-12-2003 06:56 PM
   
hi everyone....tune-up and running fine then all of a sudden really rough idle...fine at speed....checked carb and cleaned, etc...checked for vacuum leak but can't find anything...when I choke it with my hand she picks up rpm and smooths out...tried shaving cream around the intake and such to see if it was sucked in but no luck...no obvious leaks but I assume it must be big cause picks up 3-400 rpm when choked down...help please
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adragon8u
Gearhead Posts: 4768
From: Oceano, Ca. member# 2895
Registered: Mar 2003
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posted 06-12-2003 06:59 PM
I had that problem with my 289 and found the leak behind the carb where the hose to the modulator on the tranny hooks up. have you looked there? i found it by spraying starter fluid around it.
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FoMoGo
Gearhead Posts: 127
From: Motor City USA
Registered: Feb 2003
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posted 06-12-2003 07:37 PM
Spray carburetor cleaner around the base gaskets of the carb.& other vacuum fitting if it smooths out you found the leak.
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craigber
Journeyman Posts: 78
From: Vancouver, Canada
Registered: Sep 2000
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posted 06-12-2003 08:33 PM
have checked for leaks with intake cleaner and now propane....no change in rpm anywhere I have checked....yesterday she came back and idled fine for about 10 minutes but then started acting up again with the bad, rough idle...at wits end...
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craigber
Journeyman Posts: 78
From: Vancouver, Canada
Registered: Sep 2000
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posted 06-13-2003 12:00 AM
am trying some more....seems if I choke the whole carb I can stall it but if I choke off the primaries (or drop the choke down) it picks up rpm and smooths out...does this rule out the vacuum leak??
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N266fords
Gearhead Posts: 1373
From: Spokane ,WA USA
Registered: Apr 2003
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posted 06-13-2003 02:23 AM
When you say choke down you mean by hand right no with the choke on.Because when you apply the choke it has a fast idle cam that can raise your rpms as well..just checking sorry..bruce
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craigber
Journeyman Posts: 78
From: Vancouver, Canada
Registered: Sep 2000
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posted 06-13-2003 09:15 AM
when the choke is open and I cover the top of the carb over the area of the choke plate it picks up...or when I manually close the choke plate..if I cover the whole carb it stalls out...does this make sense?? sorry for being such a dweeb but carbs are not my thing...I have changed the gaskets between carb and intake...also pulled the top of the carb and changed the needles/seats plus checked all the jets....seems to be all clear...just a bad stumbling idle....
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rockafellz
Gearhead Posts: 1420
From: San Lorenzo, CA, USA
Registered: Aug 2001
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posted 06-13-2003 10:03 AM
What kinda carb is it?Erik ------------------
1966 Ford Mustang 2+2
Mine - Restomod in Progress 1966 Ford Mustang Coupe
Dad's - Original Unrestored
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craigber
Journeyman Posts: 78
From: Vancouver, Canada
Registered: Sep 2000
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posted 06-13-2003 10:07 AM
its an edelbrock 1406....everything was fine till I came off the highway one day and she didn't want to idle anymore...had just changed plugs, cap and rotor...
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indyphil
Gearhead Posts: 2255
From: Senoia, G.A. USA
Registered: Jul 2002
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posted 06-13-2003 10:34 AM
You may have a leak in the intake that is underneath and is drawing from the lifter valley. That kind of leak may come and go based on the thermal growth of the intake. You wont be able to find it with EZstart because you cant get to it. Intake leaks usually affect only one cylinder or one side.check your PCV valve and anything else that is drawing manifold vacuum (power brake booster - tranny lines etc..). ------------------
'68 coupe 289 C code
66 heads, edel 600cfm carb, performer intake, dual exhaust
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rockafellz
Gearhead Posts: 1420
From: San Lorenzo, CA, USA
Registered: Aug 2001
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posted 06-13-2003 11:18 AM
Well, you just changed the plugs, cap, & rotor. Any chance it could be the wires? Could be misfiring by a loose wire or bad wire when you were changing the plugs. Maybe it's misfiring when it's cold but the idle is too high for you to notice until it's fully warmed up and won't idle anymore.I'd base your problems around what you did prior to the idle problem. I'd at least start there. Now if you fiddled with the carb at the same time, then it may be your carb too. Sorry, not familiar with edelbrock carbs.  Erik ------------------
1966 Ford Mustang 2+2
Mine - Restomod in Progress 1966 Ford Mustang Coupe
Dad's - Original Unrestored
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craigber
Journeyman Posts: 78
From: Vancouver, Canada
Registered: Sep 2000
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posted 06-13-2003 11:57 AM
thanks...gonna checks plugs and wires right now...I checked the intake as best I could and there doesn't appear to be a leak....don't want to do another intake "turkey pan" if I don't have to!!
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craigber
Journeyman Posts: 78
From: Vancouver, Canada
Registered: Sep 2000
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posted 06-13-2003 05:53 PM
well it is finally idling although still a bit rough and such...the exhaust out the tailpipes seems to really "burble"....not smooth
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