Outer Limits 4x4 Board

G'day
i have a 91 sierra with the standard carby on it and it wont idle below 2000rpm, i checked all the vacum lines found one off, put it back on but that hasnt changed the idle, been fiddlin with the idle screw but that hasnt helped, the choke isnt stuck on as it doesnt work at all, and checked to see if intake gasket is broken but it appears to be fine. it isnt blowing black smoke either so im thinking its sucking air from some where...
Any ideas as to wat else it could be or wat else i should check?

Mundy

check the head light idle up actuator at the front of the carby, they are renowned for packing it in. it is linked via an arm to the throttle shaft.

it seems to be moving freely, pushed it both ways with engine running didnt change it at all.
any more ideas?

have you checked to see if the butterfly closes completely. if not you know it's got something to do with that area.

is the accelerator cable too tight , it may be adjusted too tight , check you have some freeplay in the cable where it links onto the throttle arm


when the car is warmed up , feel the 2 hoses that go to the top of the back of the carb , if they are cold , water isnt flowing through them to operate the wax pallette choke , the cold idle screw could be holding the revs up in that case .

when the engine is stopped , lift the throttle linkage (where the cable connects) and you will see a screw underneath , wind this out a couple of turns and then start the engine . does the revs decrease then ?

if that fixes the problem , you have to pull off the hoses and diagnose at what point the water isnt flowing to come off the cold idle setting .

hope this helps.