Bg Idle Issues
Thread Starter
Le Mans Master
Joined: Jan 2001
Posts: 6,938
Likes: 1
From: San Diego CA
Bg Idle Issues
I sent the following to LARS but also wanted to see what you gus think.
"Hey have a question for you;
Two symptoms.
1. Idle will not go below 1100 RPM
2. Idle has intermitant miss
Friday I did following;
a. Reverified transfer slots pri/ secondary are .020
b. Found A/F screws were not even, some ½ some 3/4. Reset all to 3/4 out as you did in November. Found best idle quality/ idle speed at 5/8 out all four screws.
c. Found timing at 14 initial and 31 degrees @2500rpm. Reset to 19 initial, 36 degrees @ 2500RPM and total 54 degrees @ 4000rpm with vacuum advance.
Still cannot get idle below 1100rpm. When cold she idles at 800rpm when she warms up it sits at 1100 RPM. This happened in Oct 04 when I did not have a heat shield but I made the heat shield as per your BG article and it cured that, ps the heat shield has a phenelic between the intake and the shield so there is no heat transfer, so I don't think it's that. If I turn the A/F even leaner say 1/2 open then it will take 10 minutes to warm up or she dies and she will stall at intersections so A/F is as lean as I can get, if I go richer my idle is 1300rpm or greater. Every thirty seconds or so the idle waivers up to 1200rpm down to 800rpm and back to 1100rpm. Never did that before, I always had a steady idle and I do not have a big cam.
Today I'll check out the Pertronix II ignition module, mic each plug wire and replace the plugs, honestly a waste of time/ money but I've run out of things to check for. Could the timing chain have stretched or why did the timing move from when you set it to 31 degrees@2500rpm? I don't think so becuase the timing would be erratic and it is steady under the timing light, except of course when she slightly waivers at idle.
She still drives like a raped ape at WOT with no problem, goes like a bat out of hell so it’s just an idle issue, matter of fact she’s even faster at WOT then ever before but this idle issue is bothering me.
Please help as I'm stumped.
Cheers,
David & Susan"
Any ideas??????
"Hey have a question for you;
Two symptoms.
1. Idle will not go below 1100 RPM
2. Idle has intermitant miss
Friday I did following;
a. Reverified transfer slots pri/ secondary are .020
b. Found A/F screws were not even, some ½ some 3/4. Reset all to 3/4 out as you did in November. Found best idle quality/ idle speed at 5/8 out all four screws.
c. Found timing at 14 initial and 31 degrees @2500rpm. Reset to 19 initial, 36 degrees @ 2500RPM and total 54 degrees @ 4000rpm with vacuum advance.
Still cannot get idle below 1100rpm. When cold she idles at 800rpm when she warms up it sits at 1100 RPM. This happened in Oct 04 when I did not have a heat shield but I made the heat shield as per your BG article and it cured that, ps the heat shield has a phenelic between the intake and the shield so there is no heat transfer, so I don't think it's that. If I turn the A/F even leaner say 1/2 open then it will take 10 minutes to warm up or she dies and she will stall at intersections so A/F is as lean as I can get, if I go richer my idle is 1300rpm or greater. Every thirty seconds or so the idle waivers up to 1200rpm down to 800rpm and back to 1100rpm. Never did that before, I always had a steady idle and I do not have a big cam.
Today I'll check out the Pertronix II ignition module, mic each plug wire and replace the plugs, honestly a waste of time/ money but I've run out of things to check for. Could the timing chain have stretched or why did the timing move from when you set it to 31 degrees@2500rpm? I don't think so becuase the timing would be erratic and it is steady under the timing light, except of course when she slightly waivers at idle.
She still drives like a raped ape at WOT with no problem, goes like a bat out of hell so it’s just an idle issue, matter of fact she’s even faster at WOT then ever before but this idle issue is bothering me.
Please help as I'm stumped.
Cheers,
David & Susan"
Any ideas??????
Melting Slicks
Joined: Feb 2003
Posts: 3,053
Likes: 4
St. Jude Donor '03,'11
I think you have a vacuum leak somewhere. The tip off is the wavering idle.
take a can of carb cleaner and spray around the base of the carb or wherever you think the leak might be. The idle should change when you do that when you are spraying at the point of the leak.
I'm trying to think if there's anything less messy than carb cleaner. I know you can eat off your engine and don't want to mess up the paint.
take a can of carb cleaner and spray around the base of the carb or wherever you think the leak might be. The idle should change when you do that when you are spraying at the point of the leak.
I'm trying to think if there's anything less messy than carb cleaner. I know you can eat off your engine and don't want to mess up the paint.
Last edited by turtlevette; Apr 9, 2005 at 01:02 PM.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by Cali,68,L-79
a. Reverified transfer slots pri/ secondary are .020
b. Found A/F screws were not even, some ½ some 3/4. Reset all to 3/4 out as you did in November. Found best idle quality/ idle speed at 5/8 out all four screws.
c. Found timing at 14 initial and 31 degrees @2500rpm. Reset to 19 initial, 36 degrees @ 2500RPM and total 54 degrees @ 4000rpm with vacuum advance.
Still cannot get idle below 1100rpm. When cold she idles at 800rpm when she warms up it sits at 1100 RPM.
???
b. Found A/F screws were not even, some ½ some 3/4. Reset all to 3/4 out as you did in November. Found best idle quality/ idle speed at 5/8 out all four screws.
c. Found timing at 14 initial and 31 degrees @2500rpm. Reset to 19 initial, 36 degrees @ 2500RPM and total 54 degrees @ 4000rpm with vacuum advance.
Still cannot get idle below 1100rpm. When cold she idles at 800rpm when she warms up it sits at 1100 RPM.
???
This is exactly what i have for settings with one exception.....i can control my curb idle by opening and closing the tranisiton slots....the .020 setting is an initial one and after you have done everything and set A/F ratio and timing and approximate idle rpm you go back to those adjusting screws for final idle....bob
Last edited by bobs77vet; Apr 9, 2005 at 01:03 PM.
Thread Starter
Le Mans Master
Joined: Jan 2001
Posts: 6,938
Likes: 1
From: San Diego CA
Originally Posted by turtlevette
I think you have a vacuum leak somewhere. The tip off is the wavering idle.
take a can of carb cleaner and spray around the base of the carb or wherever you think the leak might be. The idle should change when you do that when you are spraying at the point of the leak.
I'm trying to think if there's anything less messy than carb cleaner. I know you can eat off your engine and don't want to mess up the paint.
take a can of carb cleaner and spray around the base of the carb or wherever you think the leak might be. The idle should change when you do that when you are spraying at the point of the leak.
I'm trying to think if there's anything less messy than carb cleaner. I know you can eat off your engine and don't want to mess up the paint.
Good clean propane
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
David -
Just caught your PM and sent you a note with some suggestions. Basically, if the engine will idle with the throttle blades closed, you have developed a vacuum leak: The engine will only idle if it receives air, and if the throttles are closed (or cannot control idle speed), the engine is sucking air from some other place. Check also to make sure that your throttle linkage is not holding the primary throttle slightly open: Remove the throttle cable and make sure the primary throttle lever goes up against the idle speed stop. If you can't kill the engine by running the throttle blades fully closed, you have a leak somewhere...
Lars
Just caught your PM and sent you a note with some suggestions. Basically, if the engine will idle with the throttle blades closed, you have developed a vacuum leak: The engine will only idle if it receives air, and if the throttles are closed (or cannot control idle speed), the engine is sucking air from some other place. Check also to make sure that your throttle linkage is not holding the primary throttle slightly open: Remove the throttle cable and make sure the primary throttle lever goes up against the idle speed stop. If you can't kill the engine by running the throttle blades fully closed, you have a leak somewhere...
Lars
