Idle woes

[Tri-Star]

Since I ordered the Ztherapy rebuild kit i've been tinkering with my carbs. I cleaned up all the old parts and put everything together. But i'm having an idle problem. When I turn the key on a cold motor (even a warm one) it needs some help.* Once I’ve revved it a few times till idle pretty good at 1400. The problem is when I adjust all the settings to have a bit lower idle it wont stay. I have the Ztherapy video and I pretty much know how to tune it but its still giving me grief. I checked the float and jetting both are set fine and not sticking. Its driving me crazy because it revs fine it just wont idle right. Any ideas?

* I don’t have a choke cable or any of the stuff for that. I know that will fix the problem of helping it start. Until then I have to open my hood and pull them with my hands.

[Arne]

My first thought is that perhaps there is a vacuum leak somewhere. If extra air is leaking in that could cause a higher idle. If you try to drop the idle by closing the throttles, suddenly there's no fuel flowing and it dies. So that would be my first step, to look for possible vacuum leaks.

[240ZX]

Tristan,

Before attempting to tune the carbs, be sure that you have done all the other engine tune-up things......timing, plugs, points (if you have them), valves, etc., etc. No sense in trying to tune the carbs if the engine is not in spec. And as Arne mentioned, be sure you have no vacuum leaks.

[mlc240z]

240ZX is giving good advice.

had an erratic idle until i adjusted valves. problem went away.

if it persists after all adjustments are done and you've checked for any external vacuum leaks as Arne suggests, it might be that the throttle plate shaft bushings are shot.

put a glob of heavy bearing grease on both sides of the carbs where the throttle plate rod ends(not sure of the exact term) come out. this will temporarily seal any vacuum leaks and allow you to verify if this is the problem. if you have air leaking there, it's not metered and can screw up your idle mixture.

[Tri-Star]

when i was cleaning up my engine bay i disconected and recondected all the hoses are wires (cleaning connections/tighting clamps ect) then i went back and tryed adjusting the carbs again but with some help. Either way it idles solid at 900. I have to do a full tune up(cap roter plugs ect) so after im done with that hopefully ill be able to fine tune it a bit more. Thanks for the help!