Idle problem - a little long
Thread Starter
Racer
Joined: Oct 2005
Posts: 427
Likes: 0
From: Cary Illinois
Idle problem - a little long
Ok, I'll try to keep this short.
My 68 L79 has had an issue whereby the idle (when choke is off and fully warm) will idle at a steady 750 RPM, but after driving, the idle will sit at 900 to 1000 RPM. It will then SLOWLY creep back down to a steady 750 if given a minute or two (or sometimes more.)
Now, if I blip the throttle while it's idling high, it will usually drop back down to 750 a little quicker. This same issue has happened with two different carbs (Both Quadrajets - one brand new and rebuilt.)
The timing is set per Lars, choke is fully off, throttle cable is new and not binding, stock everything under the hood with stock open air element..
When I pull the PCV and plug it, the idle will drop down all on it's own. So...I threw on a new PCV and took it for a spin - same deal - high idle at 1000 that slowly drops on it's own.
I'm out of ideas. Anything anyone can think of that I'm missing???
Could it possibly be that I need to "block off" part of the PCV to make it idle a bit lower????
I'm plum out of ideas.
Thanks in advance!
Q
My 68 L79 has had an issue whereby the idle (when choke is off and fully warm) will idle at a steady 750 RPM, but after driving, the idle will sit at 900 to 1000 RPM. It will then SLOWLY creep back down to a steady 750 if given a minute or two (or sometimes more.)
Now, if I blip the throttle while it's idling high, it will usually drop back down to 750 a little quicker. This same issue has happened with two different carbs (Both Quadrajets - one brand new and rebuilt.)
The timing is set per Lars, choke is fully off, throttle cable is new and not binding, stock everything under the hood with stock open air element..
When I pull the PCV and plug it, the idle will drop down all on it's own. So...I threw on a new PCV and took it for a spin - same deal - high idle at 1000 that slowly drops on it's own.
I'm out of ideas. Anything anyone can think of that I'm missing???
Could it possibly be that I need to "block off" part of the PCV to make it idle a bit lower????
I'm plum out of ideas.
Thanks in advance!
Q
Burning Brakes
Joined: Jun 2005
Posts: 764
Likes: 2
From: THE OLDER I GET THE BETTER I WAS! NORTHERN ONTARIO
I wonder if the PCV is taking you in the wrong direction? Just thinking that maybe the return spring might be weak...or maybe bad base plate carb gasket? A place to start looking... any way just a thought
Thread Starter
Racer
Joined: Oct 2005
Posts: 427
Likes: 0
From: Cary Illinois
Good ideas. The return spring is new and I did try a heavier spring just to see if it would make a difference - nope.
I didn't try a different base gasket so I will give that a try.
The throttle shafts were a bit loose on the 1st carb. The 2nd which is on it now was nice and tight with no play.
I didn't try a different base gasket so I will give that a try.
The throttle shafts were a bit loose on the 1st carb. The 2nd which is on it now was nice and tight with no play.
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Le Mans Master
Joined: Jan 2006
Posts: 8,319
Likes: 7
From: Wilmington DE, Drive it like you stole it, 68 327 4 speed coupe
Ok, I'll try to keep this short.
My 68 L79 has had an issue whereby the idle (when choke is off and fully warm) will idle at a steady 750 RPM, but after driving, the idle will sit at 900 to 1000 RPM. It will then SLOWLY creep back down to a steady 750 if given a minute or two (or sometimes more.)
Now, if I blip the throttle while it's idling high, it will usually drop back down to 750 a little quicker. This same issue has happened with two different carbs (Both Quadrajets - one brand new and rebuilt.)
The timing is set per Lars, choke is fully off, throttle cable is new and not binding, stock everything under the hood with stock open air element..
When I pull the PCV and plug it, the idle will drop down all on it's own. So...I threw on a new PCV and took it for a spin - same deal - high idle at 1000 that slowly drops on it's own.
I'm out of ideas. Anything anyone can think of that I'm missing???
Could it possibly be that I need to "block off" part of the PCV to make it idle a bit lower????
I'm plum out of ideas.
Thanks in advance!
Q
My 68 L79 has had an issue whereby the idle (when choke is off and fully warm) will idle at a steady 750 RPM, but after driving, the idle will sit at 900 to 1000 RPM. It will then SLOWLY creep back down to a steady 750 if given a minute or two (or sometimes more.)
Now, if I blip the throttle while it's idling high, it will usually drop back down to 750 a little quicker. This same issue has happened with two different carbs (Both Quadrajets - one brand new and rebuilt.)
The timing is set per Lars, choke is fully off, throttle cable is new and not binding, stock everything under the hood with stock open air element..
When I pull the PCV and plug it, the idle will drop down all on it's own. So...I threw on a new PCV and took it for a spin - same deal - high idle at 1000 that slowly drops on it's own.
I'm out of ideas. Anything anyone can think of that I'm missing???
Could it possibly be that I need to "block off" part of the PCV to make it idle a bit lower????
I'm plum out of ideas.
Thanks in advance!
Q
tim
Last edited by sweethence; Sep 3, 2008 at 10:08 AM.
Intermediate
Joined: Jun 2008
Posts: 25
Likes: 0
Ok, I'll try to keep this short.
My 68 L79 has had an issue whereby the idle (when choke is off and fully warm) will idle at a steady 750 RPM, but after driving, the idle will sit at 900 to 1000 RPM. It will then SLOWLY creep back down to a steady 750 if given a minute or two (or sometimes more.)
Now, if I blip the throttle while it's idling high, it will usually drop back down to 750 a little quicker. This same issue has happened with two different carbs (Both Quadrajets - one brand new and rebuilt.)
The timing is set per Lars, choke is fully off, throttle cable is new and not binding, stock everything under the hood with stock open air element..
When I pull the PCV and plug it, the idle will drop down all on it's own. So...I threw on a new PCV and took it for a spin - same deal - high idle at 1000 that slowly drops on it's own.
I'm out of ideas. Anything anyone can think of that I'm missing???
Could it possibly be that I need to "block off" part of the PCV to make it idle a bit lower????
I'm plum out of ideas.
Thanks in advance!
Q
My 68 L79 has had an issue whereby the idle (when choke is off and fully warm) will idle at a steady 750 RPM, but after driving, the idle will sit at 900 to 1000 RPM. It will then SLOWLY creep back down to a steady 750 if given a minute or two (or sometimes more.)
Now, if I blip the throttle while it's idling high, it will usually drop back down to 750 a little quicker. This same issue has happened with two different carbs (Both Quadrajets - one brand new and rebuilt.)
The timing is set per Lars, choke is fully off, throttle cable is new and not binding, stock everything under the hood with stock open air element..
When I pull the PCV and plug it, the idle will drop down all on it's own. So...I threw on a new PCV and took it for a spin - same deal - high idle at 1000 that slowly drops on it's own.
I'm out of ideas. Anything anyone can think of that I'm missing???
Could it possibly be that I need to "block off" part of the PCV to make it idle a bit lower????
I'm plum out of ideas.
Thanks in advance!
Q
This cured my problem hope it helps you .
I noticed idle scew was not touching plate so I set idle speed with idle screw to 1200 rpm which is too high then unscrewed jets equally until
I reached desired rpm for me it was 800rpm. Never had problem since.