How do you lower the idle?
Thread Starter
Burning Brakes
Joined: Sep 2006
Posts: 967
Likes: 0
How do you lower the idle?
Hello.
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I need to lower my idle. When it's good and hot after a drive the rpms in park or nuetral are 1500 and when I shut it off it will start back up like maybe one out of every ten times.
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The engine is a 1974 l48 engine in my 1977 corvette. The engine has an edelbrock 1406 electric choke carb on it.
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I have the idle speed screw backed all the way out and I have tried adjusting the idle mixture screws to lower the idle. The problem with this pat is I think it leans out too much and it overheats.
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The way it is right now it'll cruise around under 40 all day at 200 but it I lean it out a little to combat the high idle it runs close to 220.
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Maybe turning the distributor? I'm pretty sure it's close to dead on timing. I have tried turning it a little and it overheated again.
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What are my options?
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Thanks.
-
I need to lower my idle. When it's good and hot after a drive the rpms in park or nuetral are 1500 and when I shut it off it will start back up like maybe one out of every ten times.
-
The engine is a 1974 l48 engine in my 1977 corvette. The engine has an edelbrock 1406 electric choke carb on it.
-
I have the idle speed screw backed all the way out and I have tried adjusting the idle mixture screws to lower the idle. The problem with this pat is I think it leans out too much and it overheats.
-
The way it is right now it'll cruise around under 40 all day at 200 but it I lean it out a little to combat the high idle it runs close to 220.
-
Maybe turning the distributor? I'm pretty sure it's close to dead on timing. I have tried turning it a little and it overheated again.
-
What are my options?
-
Thanks.
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
You don't fix idle speed by adjusting idle mixture or timing. Idle speed is adjusted with the idle speed screw.
If the engine will idle with the throttle blades fully closed, it means you have a vacuum leak (the air, if not going through the throttle blades, has to be coming from somewhere).
First step is to verify that the throttle blades really are fully closed. Make sure the cable is not holding them open. Pull the carb and flip it upside-down and make sure they fully close. If the blades are fully closed and not allowing air through, and the idle is still high, you have a vacuum leak.
If the engine will idle with the throttle blades fully closed, it means you have a vacuum leak (the air, if not going through the throttle blades, has to be coming from somewhere).
First step is to verify that the throttle blades really are fully closed. Make sure the cable is not holding them open. Pull the carb and flip it upside-down and make sure they fully close. If the blades are fully closed and not allowing air through, and the idle is still high, you have a vacuum leak.
