Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 4x4 Cowboy, Jan 22, 2003.
how can i lower the idle on my truck i have a 350 with a quadra-jet 4b.
depends on when it is idling to high. When cold? When hot? There should be an idle screw on the carb that acts as a linkage stop that will adjust the idle.
no matter what temp outside when i first start up the truck it real high. if i threw it into drive it would take off.(ive did it and it hit 40 mph) ya so start up idle is real high.
If you adjust the throttle stop and the idle won't go down, maybe the linkeage between the primary and secondary throttle plates has been bent. You can't bend the linkeage to make the secondaries on a q-jet open sooner. Take the air cleaner off and see what's going on.
First, check for vacuum leaks.
then check your choke settings.( Get some sort of manual that tells you how to adjust this system, its too hard to explain w/out pictures)
If they are alright, adjust the idle screw.
If the linkage between the primaries and secondaries is bent it won't make a difference in idle unless the spring tension on the air valve spring has been taken off. Yes the throttle blades will be open but there shouldn't be enough vacuum to pull open the air valve, and therefore should be no fuel or air going in from the secondary side.
I hear what your saying, but from experience I bent mine and when I started the truck the idle jump to over 2500 RPM. Engine was already warm. This was a slight bend and when I bent it back idle dropped to 750RPM. I did this prior to reading Roe's book on the Rochester Qaudrajet.
Idle speed screw is on the drivers side of the carb. Screwdriver is used from the front of the truck. Look at the base of the carb right near where the primary linkage hooks up.
Lots of times idle is turned way up to hide something such as a vacuum leak, so if you bought it this way, be prepared to fix other problems.
If it just started happening, the idle screw isn't the problem, nor is linkage. Stuff doesn't bend or adjust itself on its own, so if it just "started happening", something is messed up that needs corrected. Of course, something may be bent NOW if something else screwed up first, but it really depends on *when* the problem started on how to tackle the problem.
You might have a worn out throttle return spring. That would be an easy fix. I had that problems and it took like 5 posts before we figured it out. /forums/images/graemlins/crazy.gif
Separate names with a comma.