I replace my hitachi carb on my 87 gl with one that I rebuilt, so now to funny stuff.....

 

I had a high idle at about 2500 rpm, after tinkering with that idle screws, I had got it do to about 1400 rpm. my car usually idles at 700 to 1000 , so I turned the screw again and the idle went up. When I went out today to try to get it down to normal, I turn the key and she turned on. But my motor almost instantly shot up to red line, it's like the gas petal all the way down.

I quickly turned the car off and pulled the top of the air box off. I noted that the butterfly was open all the way. when I close it, It stays open about an 1/8 of inch.

 

Any ideas about how to fix this?

Edited February 14, 201214 yr by ontherun987

the butterfly for the choke, or the throttle? in it's final days, my hitachi gave me idling fits too

the butterfly for the choke, or the throttle? in it's final days, my hitachi gave me idling fits too

 

 

 

 

it's the butterfly for the choke

after some tinkering with the fast idle screw I got it down to about 3000 rpm

Now it burning rich, now sure where to go from here.

Have you retightened the carb? After you rebuild a carb and install it on the car, it's a good idea (due to vibration while running) to take it off again and go over every bolt on it and retighten it. Don't mean disassemble it again, i mean all the bolts that mate the different parts of it together. Just make sure it's all tight.

This suggestion comes from the old Rochester carbs I rebuilt for 70's chevys.

Retighten it down to the manifold too after a bit.

how do I adjust the air and fuel mix?

Hey man.

 

Sounds like your throttle plates arn't closing fully. I would be focussing on throttle linkage and return springs. Also maybe a sticky throttle cable.

 

As other have already mentioned, check for air leaks. Make sure all vacuum ports are connected/blocked off.

 

If you have vacuum secondary it would pay to check that it is connected to the correct port. It should be connected via a port at the back that runs of venturi vacuum not manifold vacuum.

 

Idle mixture screw is just that. I has little affect on driving conditions. Yes it nedds to be set correctly but it will not be the main cause of your fast idle.

 

Cheers

 

Dirk

 

P.s. Also need to address the choke plate. Manual or auto choke?

After checking my vacuum lines and tinkering with the adjustment screws it now idles at about 600 to 800 rpm. As for it burning rich, seems to have evened out after the idle adjustments.