Q-Jet warm idle ... Too high, need help
Thread Starter
Instructor
Joined: May 2001
Posts: 186
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From: CT, USA
Q-Jet warm idle ... Too high, need help
This is not a new problem but I'm just getting around to looking into it. The engine runs great and I am getting a very smooth idle of about 950 rpm. The adjustment screw is backed all the way off so that when the throttle returns it doesn't even hit the stop. How can I drop the idle down to about 800? :confused: As always, any help is much appreciated.
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
Re: Q-Jet warm idle ... Too high, need help (rafox77)
rafox -
First, check out the fast idle system on the passenger side of the carb. Make sure that the fast idle cam is dropping all the way down, and that the fast idle screw on the passenger side is not contacting the fast idle cam once the choke is fully opened: it is possible to assemble the fast idle cam in such a way that it does not fully retract.
If the fast idle screw is not contacting the cam, and the throttle lever does not contact the warm idle stop screw, pull your throttle cable off the carb and see if this allows the engine to idle down. If it does, adjust your throttle cable. If it still does not idle down, it's time to yank the carb off and check it out:
With the carb off, verify that the throttle blades actually close all the way with the idle screws backed off. Verify, also, that the secondary throttle blades are fully closed with no air gaps. If the throttles all close completely tight and you still have a fast idle problem, you have a vacuum leak somewhere. Best approach is to cap off every single vacuum port on the carb, verify that the base gasket is correct, and then bolt it up and run it. One by one, re-connect the vacuum accessories until the fast idle problem re-appears - fix the problem from there.
If you can't find the problem, let me know and I'll send you out one of the Forum Loaner Carbs to help you troubleshoot the problem: If you get a fast idle with one of the loaners, you have a problem other than the carb. If the Loaner solves the problem, you need to do some carb work.
First, check out the fast idle system on the passenger side of the carb. Make sure that the fast idle cam is dropping all the way down, and that the fast idle screw on the passenger side is not contacting the fast idle cam once the choke is fully opened: it is possible to assemble the fast idle cam in such a way that it does not fully retract.
If the fast idle screw is not contacting the cam, and the throttle lever does not contact the warm idle stop screw, pull your throttle cable off the carb and see if this allows the engine to idle down. If it does, adjust your throttle cable. If it still does not idle down, it's time to yank the carb off and check it out:
With the carb off, verify that the throttle blades actually close all the way with the idle screws backed off. Verify, also, that the secondary throttle blades are fully closed with no air gaps. If the throttles all close completely tight and you still have a fast idle problem, you have a vacuum leak somewhere. Best approach is to cap off every single vacuum port on the carb, verify that the base gasket is correct, and then bolt it up and run it. One by one, re-connect the vacuum accessories until the fast idle problem re-appears - fix the problem from there.
If you can't find the problem, let me know and I'll send you out one of the Forum Loaner Carbs to help you troubleshoot the problem: If you get a fast idle with one of the loaners, you have a problem other than the carb. If the Loaner solves the problem, you need to do some carb work.
Thread Starter
Instructor
Joined: May 2001
Posts: 186
Likes: 0
From: CT, USA
Re: Q-Jet warm idle ... Too high, need help (lars)
Now that's what this forum is all about ... ask a question and someone who knows what they're talking about will point you in the right direction. I won't get all choked up (no pun intended) about this but this is the best place for folks that love their vettes and want to help each other out :cheers: Thanks for the reply Lars, I'll let you know what I find out.
Rick
Rick
