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Idleing high 1980 brat


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19 replies to this topic

#1 disom93

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Posted 25 August 2013 - 08:17 AM

Can anyone tell me why my brat randomly decides to either not idle of idle 2500-3000. And it will idle fine at 1200 but below that it cuts out and dies. And adjusting the mix screw does nothinf even if turned all the way in???? Help!

#2 caspice

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Posted 25 August 2013 - 08:40 AM

When was the carb last rebuilt? Indescriminately changing the fuel-air mixture ratio may compound your issue. Do you have a FSM? If it is randomly kicking into a high idle start with examining the electric choke. If it will not idle under 1200 rpm your problem may stem from clogged idle jets, bad fuel mixture, incorrect timing. Verify the PCV valve and hoses are clear.
Years back picked up a great condition low mileage GL hatchback for a few bills because it wouldn't idle and could not be driven over twenty mph. The cause was a bad PCV and clogged breather hoses.

#3 disom93

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Posted 25 August 2013 - 08:44 AM

Carb was just rebuilt due to a sputtering issue and it idled before so im not sure whats wrong i may have did something. But it runs great just wont run below 1200 or idle an randomly its like the rpms hang when u shift or it high idles bad any help would be appreciated im lost

#4 RCW

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Posted 26 August 2013 - 11:29 AM

Check your vacuum hoses, leaks result in high idle and cutting out if you try to lower it



#5 disom93

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Posted 26 August 2013 - 01:44 PM

There are two vacum lines in the front but dont feel like they have any vacum or suction on em? One goes into carb by a nipple

#6 djellum

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Posted 26 August 2013 - 01:46 PM

rev the motor while you check.  they are probably ported vacuum so they increase the vacuum with engine speed rather than being max at idle.



#7 disom93

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Posted 26 August 2013 - 01:55 PM

Would that make it randomly idle high and sometimes not idle at all but still run good??

#8 RCW

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Posted 26 August 2013 - 03:20 PM

Not the ported lines, check for any lines that go under the manifold where the rubber hoses connect to metal. Sometimes you can hear the leak.



#9 disom93

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Posted 26 August 2013 - 04:26 PM

Looked about taking the emulsion tubes out tp clean in carb and cant seem to get them out how do they come out? And all vacum lines look right

#10 disom93

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Posted 26 August 2013 - 10:03 PM

Anyone have any idea on how the emulsion tubes come out?

#11 ivans imports

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Posted 27 August 2013 - 09:08 AM

Take off top of carb and unscrew them doubt is you problem check intake gaskets are they factory subaru only ? also check that choke is pulling off and idle curcit in carb have had luck putting my hand over the top at high rpms thiss will stall it but pulls the crap outa the bottom of carb may have to do it more than one time but seems to work on old hitachis



#12 disom93

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Posted 27 August 2013 - 03:57 PM

Ok u take top off abd there a jet above the emulsion tube it comes off fine but the tubes stay in? How do they thread out? And its got new gaskets. Im not sure how to check the choke its open tho and moves when u rev it

#13 ivans imports

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Posted 28 August 2013 - 09:26 AM

choke should be closed cold and move to fully open as it warms up also should be a good power signal at choke + post



#14 disom93

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Posted 28 August 2013 - 10:57 PM

Ok the choke is open. Idk whats the issue. It will sometimes idle high and sometimes not idle at all? ?

#15 disom93

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Posted 28 August 2013 - 10:59 PM

Also how do i check the idle circuit??

#16 ivans imports

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Posted 29 August 2013 - 09:46 AM

I dont remember off hand but shure a manual will have a good blow up pic of carb i think its in the lower half



#17 disom93

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Posted 29 August 2013 - 01:25 PM

Is there something to check specificly or what could be causing it

#18 ferox

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Posted 29 August 2013 - 04:00 PM

There are two vacum lines in the front but dont feel like they have any vacum or suction on em? One goes into carb by a nipple

 

Are you saying that the two vacuum ports on the front of the carb are not being used and are not capped?  Both ports should have a nipple btw.

 

If the idle mix screw has no effect on the idle quality or speed, and everything else is intact, then it means you have by-passed the idle-circuit in the carb.  The idle mix screw should be roughly two full turns out from being lightly seated plus or minus a half turn.

 

Most likely you have some vacuum leaks.  If you messed with the fast idle screw on the carb, that can complicate matters as well.

 

Since you rebuilt the carb and idle/driveability issues still persist, you probably need to check all vacuum lines coming off the manifold (brake booster, charcoal canister valve, canister purge line, etc,..) as well as the intake manifold gaskets.

 

Does the behavior change as the engine warms up?


Edited by ferox, 29 August 2013 - 04:01 PM.


#19 disom93

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Posted 29 August 2013 - 05:17 PM

Doesnt change when warm it was a diffrent issue is why i rebuilt carb then this started how do i see if i have bypassed idle circuit???

#20 disom93

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Posted 29 August 2013 - 05:18 PM

And all vacum lines are hooked where there supposed to be. How do i check this "idle circuit?




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