3.8 dualjet part throttle hitch

[Clone TIE Pilot]

You can't tune a CCC carb without some kind of meter to read the dwell. You are working blind without a meter. The idle screws are the coarse idle adjustment, the idle air bypass valve screw is the fine adjustment. It also affects the position of the throttle blades at idle along with base ignition timing. Have the throttle blades too far open at idle and you get nozzle drip, too far closed and you get off idle stumble. You use base timing and idle air bypass to get your throttle blade angle into the sweet area at idle.

 

[jiho]

True about the dwell meter. Which adjust is coarse and which is fine varies. For mine, the air bleed gets a fixed setting and then you fine-tune the mixture screws. For many it's the exact opposite. I keep forgetting that, my head's too far into mine. Way too far.

Either way the adjustment does affect off-idle. The Buick V6 never has a very smooth idle.

 

[jiho]

i turned the needle adjustment 1/2 turn rich from "base" and my hitch got a lot better

The needles I speak of are the ones the solenoid actuatates. Probably should have said rods.

What adjustment did you turn for those?

 

[TURNA]

Put an emery board nail file one of the cheap thin cardboard type between the accelerator pump arm and accelerator pump plunger.

See if that makes a difference when you drive.

Sounds like a flat spot in the pump

 

[pontiacgp]

True about the dwell meter. Which adjust is coarse and which is fine varies. For mine, the air bleed gets a fixed setting and then you fine-tune the mixture screws. For many it's the exact opposite. I keep forgetting that, my head's too far into mine. Way too far.

Either way the adjustment does affect off-idle. The Buick V6 never has a very smooth idle.

the idle screws do affect off idle mixture, my A/F wideband can confirm that

 

[a.graham52]

What adjustment did you turn for those?

The height adjustment for the solenoid.

 

[jiho]

I think the technical term for that would be the Rich Mixture Stop Screw. It is supposed to have a fixed setting, so the rods bounce a certain distance between that and the Lean Mixture Stop Screw setting. You shouldn't have to try to adjust the mixture that way, if the rod distance is to spec.

Interesting way to do it, though. Certainly easier than the Idle Mixture Screws.

Meanwhile, I'm wondering if maybe you might have a vacuum leak somewhere. There are so many opportunities for one.

 

[pontiacgp]

This is worth repeating, have you bought a dwell meter yet?

You can't tune a CCC carb without some kind of meter to read the dwell. You are working blind without a meter. The idle screws are the coarse idle adjustment, the idle air bypass valve screw is the fine adjustment. It also affects the position of the throttle blades at idle along with base ignition timing. Have the throttle blades too far open at idle and you get nozzle drip, too far closed and you get off idle stumble. You use base timing and idle air bypass to get your throttle blade angle into the sweet area at idle.

 

[jiho]

There are also opportunities for fuel delivery problems.

Which is what I seem to have right now. Give it enough load and it will drain the float bowl. Most likely I botched a recent tank swap somehow. Since the fuel filter didn't fix it (as elaborate a fiasco as that turned into), now I have to track the problem down in the lines, pump or tank itself. Ugh. Why I checked out every other possibility first.

Sorry if I seem to be thrashing around in someone else's thread. Kind of a walk-in rant.

 

[Clone TIE Pilot]

The idle air bypass allows air to bypass the throttle plates when closed at idle. This allows the throttle plates to be further closed to prevent nozzle drip. But if they are too far closed, the off idle ports kick in late causing a just off idle stumble which sounds like your problem. Another problem it could be is if the accel pump seal was a low quality replacement that swelled. Cheap rebuild kits will bite you. Vacuum leaks will also cause idle and off idle issues. According to my Buick repair book, you just set the idle screws on a CCC Djet from 3 to 3.5 turns, then tune it with the IAB valve using a dwell meter.

As for M/C solenoid plunger travel, you adjust it to factory specs and forget it. You have to be very careful with the M/ C screw as it is easy to strip and ruin the carb. There used to be special repair kits but they are discontinued and hard to find NOS.