jmspep Posted November 3, 2014 Report Share Posted November 3, 2014 So i have had a high idle for quite sometime now and just changed my spark plugs and tried to change the idle but now have mad it worse. i can put it in 3rd gear and not give it throttle and cruise down the road. i can work on four barrel carbs but know nothing about these. Any thoughts, only screw i know of is the throttle screw.. here is the carb i have. Quote Link to comment
EastBay521 Posted November 3, 2014 Report Share Posted November 3, 2014 Vaccum leak? Quote Link to comment
trjerm Posted November 3, 2014 Report Share Posted November 3, 2014 I just fixed a high idle on my 85, by making sure the large tube to the bottom of the air cleaner assy was fully seated. I'd bet that your vaccum lines aren't up to snuff. Spend the afternoon and go thru all of them. You should have a vaccum diagram for your 720 on the inside of the hood. Quote Link to comment
arizonajones Posted November 3, 2014 Report Share Posted November 3, 2014 Make sure your choke is opening completely up after 5 or so minutes - if not, could be a burnt fuse. Also, check your fast idle adjustment screw (visible from underside of the carb.) I had a similar problem - choke fuse blew, didn't open fully and sat on the fast idle screw while running extra rich. Quote Link to comment
jmspep Posted November 3, 2014 Author Report Share Posted November 3, 2014 Hm fast idle screw.....? old sprak plugs were black with oil :thumbup: Quote Link to comment
xHighOctanex Posted November 4, 2014 Report Share Posted November 4, 2014 When I bought mine my fast idle was all screwed up, I'd start the truck up with this insane idle (didn't have a tach back then so not sure exacts). We pulled the carburetor off twice just to adjust it. The base of mine was also really lose from whoever owned it before me. Quote Link to comment
arizonajones Posted November 4, 2014 Report Share Posted November 4, 2014 Also, this page might be useful to you: http://forums.nicoclub.com/z24-carb-rebuild-diy-1984-86-t537596.html Quote Link to comment
datzenmike Posted November 5, 2014 Report Share Posted November 5, 2014 The fast idle adjustment shouldn't need to be touched. It is set at the factory to open the primary a set amount. This will give a fast idle if 1,800 to 2,200 RPMs. Without a tach to tell you the RPMs, simply thinking it seems high is just an opinion. As mentioned check that when warmed up the choke is fully open or off. If the choke is partly on the fast idle cam may be also. Hold the throttle half way open and close and open the choke plate. You should see the fast idle cam drop down when the choke is closed and rise up out of the way when the choke is opened. WD-40 or use carb cleaner on all the linkages around the fast idle cam to clean and lube them. Once you are sure that the fast idle cam is not causing this check that the throttle cable is not too tight and holding the throttle open slightly. Next look down the secondary barrel with a flash light. The throttle plate should be fully closed but possibly something is caught in it or it is just stuck. Quote Link to comment
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.