qjet idle and mixture screws

[wazzabie]

I was able to get he fast idle to the specified rpms.

I'm unable to get the idle screw to the 700rpms. It is at 400rpms or 1K+ rpms.

Also as I trurn the two mixture screws there is not much of a responce. Turned way in I hear the engine stumble. As I turn them out I don't get much responce in rpms or vacum.

THis is as stock qjet on a 78 K5 no cali emissions.

How much responce should the mixture screws provide? How much should the rpms change as I turn them?

Why is the idle screw either at 400rpms or 1K+. I need to set it at 700prm.

 

[tRustyK5]

Is your choke fully opening? If not, when you turn in the idle speed screw it'll push the linkage onto the first high idle step. Mixture screws won't do much until you get your idle speed down.

I like to set mixture screws at a very low idle, like 500 rpm. You can then really notice the small differences they make.

Rene

 

[wazzabie]

Is your choke fully opening? If not, when you turn in the idle speed screw it'll push the linkage onto the first high idle step. Mixture screws won't do much until you get your idle speed down.

I like to set mixture screws at a very low idle, like 500 rpm. You can then really notice the small differences they make.

Rene

How can I tell if the choke is fully opening?

 

[Big Ray]

FYI, those things are nearly impossible to tune if the throttle shaft bores are worn. If will suck air until they are repaired.

I love Q-jets, they are awesome when properly set up...


these will fix your throttle shaft bores....linky

 

[tRustyK5]

How can I tell if the choke is fully opening?

The choke plate should be vertical when the engine is warm. What 62 said is also true...if your throttle shaft bores are worn you won't be able to tune it at all as it'll always be cheating air at that point. Make sure the choke is 100% open first...if you're still having issues examine the throttle bores more closely. You can check them by grabbing the throttle lever and seeing if there is any up and down play.

Rene

 

[wazzabie]

The choke plate should be vertical when the engine is warm. What 62 said is also true...if your throttle shaft bores are worn you won't be able to tune it at all as it'll always be cheating air at that point. Make sure the choke is 100% open first...if you're still having issues examine the throttle bores more closely. You can check them by grabbing the throttle lever and seeing if there is any up and down play.

Rene

Throttle body is good. I had a carb shop check it out when the chemdip the card for me. I just rebuilt it not that long ago.

I made a big mistake however and may have gotten a bunch of metal shavings down the carb. I forgot to put on the air cleaner when I ran it. So hot exhaust was going in directly. The exhast is rusting.

I'll try again and make sure the choke is 100%.

 

[K85 Octane]

Throttle body is good. I had a carb shop check it out when the chemdip the card for me. I just rebuilt it not that long ago.

I made a big mistake however and may have gotten a bunch of metal shavings down the carb. I forgot to put on the air cleaner when I ran it. So hot exhaust was going in directly.

totally lost me after this one

throttle body? Metal shavings? Didn't put the hat on and got exhaust in?