Can't get the idle down
Thread Starter
Safety Car
Joined: Dec 2004
Posts: 4,876
Likes: 1
From: Jersey Shore Exit 98
Can't get the idle down
I installed a new LT-1 350 but reused my Q-jet. I did punch out the caps over the mixture screws to give the new motor more gas. The old L48 ran lean. Now I can't get a the car to idle. I'm looking for 1000rpm's but it stays or revs on its own to 2000?? Once its hot I get it down but its like it has a mine of its own & floats up & down??
Any helpful advise.
Thanks
Jim
Any helpful advise.
Thanks
Jim
Melting Slicks
Joined: Aug 2002
Posts: 3,334
Likes: 4
From: Midland TX
You've probably already checked these but it was problems I ran into...
* Check for vacuum leaks. I use carb cleaner and spray around gaskets, etc.
* Idle screw all the way out?
* Check throttle cable adjustment. Mine was back a little far and held the throttle open a little.
* Is the cold idle coming off when hot? I had to make some adjustments to my cold idle speed too.
* Check for vacuum leaks. I use carb cleaner and spray around gaskets, etc.
* Idle screw all the way out?
* Check throttle cable adjustment. Mine was back a little far and held the throttle open a little.
* Is the cold idle coming off when hot? I had to make some adjustments to my cold idle speed too.
Thread Starter
Safety Car
Joined: Dec 2004
Posts: 4,876
Likes: 1
From: Jersey Shore Exit 98
You've probably already checked these but it was problems I ran into...
* Check for vacuum leaks. I use carb cleaner and spray around gaskets, etc.
* Idle screw all the way out?
* Check throttle cable adjustment. Mine was back a little far and held the throttle open a little.
* Is the cold idle coming off when hot? I had to make some adjustments to my cold idle speed too.
* Check for vacuum leaks. I use carb cleaner and spray around gaskets, etc.
* Idle screw all the way out?
* Check throttle cable adjustment. Mine was back a little far and held the throttle open a little.
* Is the cold idle coming off when hot? I had to make some adjustments to my cold idle speed too.
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
I installed a new LT-1 350 but reused my Q-jet. I did punch out the caps over the mixture screws to give the new motor more gas. The old L48 ran lean. Now I can't get a the car to idle. I'm looking for 1000rpm's but it stays or revs on its own to 2000?? Once its hot I get it down but its like it has a mine of its own & floats up & down??
Any helpful advise.
Thanks
Jim
Any helpful advise.
Thanks
Jim
Thread Starter
Safety Car
Joined: Dec 2004
Posts: 4,876
Likes: 1
From: Jersey Shore Exit 98
Maybe I can get Lars to rebuilt it over the winter.
Pro
Joined: Sep 2004
Posts: 595
Likes: 0
From: Boston MA
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,391
From: At my Bar drinking and wrenching in Lafayette Colorado
Send it out and I'll take a look at it.
But if your idle is at 2000 rpm, you have something other than worn throttle shafts going on. A worn throttle shaft will typically cause an inconsistent return to idle, and you can get it to idle right by wiggling the throttle lever.
In order for the engine to idle at 2000 rpm, it has to be sucking the air and fuel from someplace. That air is either coming through the throttle blades due to the blades not fully closing (either primary or secondary side), or there is a vacuum leak allowing air into the engine. Check throttle linkage to make sure the linkage is not holding the throttle open. Check the primary throttle to make sure it actually fully closes when you back out the idle speed screw. Check the secondary throttle blades and make sure they are fully seated and sealed in the throttle bores - you can tap them with a screwdriver to seat them - 3 taps only, please...
If all blades are fully closed and sealed in the bores and the engine is still running, you have a vacuum leak from some source.
But if your idle is at 2000 rpm, you have something other than worn throttle shafts going on. A worn throttle shaft will typically cause an inconsistent return to idle, and you can get it to idle right by wiggling the throttle lever.
In order for the engine to idle at 2000 rpm, it has to be sucking the air and fuel from someplace. That air is either coming through the throttle blades due to the blades not fully closing (either primary or secondary side), or there is a vacuum leak allowing air into the engine. Check throttle linkage to make sure the linkage is not holding the throttle open. Check the primary throttle to make sure it actually fully closes when you back out the idle speed screw. Check the secondary throttle blades and make sure they are fully seated and sealed in the throttle bores - you can tap them with a screwdriver to seat them - 3 taps only, please...
If all blades are fully closed and sealed in the bores and the engine is still running, you have a vacuum leak from some source.
Last edited by lars; May 24, 2007 at 09:50 AM.
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Thread Starter
Safety Car
Joined: Dec 2004
Posts: 4,876
Likes: 1
From: Jersey Shore Exit 98
