Idle Mixture

[Ray K.]

I have an '82 with a 350 crate motor equipped with a Quadrajet carb. The engine / carb have approximmately 7,000 miles on them. Lately the engine quits running when the A/C is turned on. It also quits when doing a slow sharp turn, as when parallel parking. Both problems occur when the engine is fully warmed and idling smoothly at 750 RPM. My initial thought is that perhaps the idle mixture could be adjusted slightly richer (along with appropriate adjustment to the idle speed) to get more torque at 750 RPM. However, the idle mixture adjustment screws have oblong-shaped heads with two flats and are placed in recessed openings in the base of the carb. Is there a special tool for adjusting the idle mixture on this make / model year carburetor?

[Gunslinger]

It might be a couple of things. The floats may be sunk or in need of adjusting. There is probably a solenoid on the carb that keeps the idle from dropping when the a/c is turned on...it could be out of adjustment or bad. From your description I would look at the solenoid first. They used to be called anti-stall dashpots but they became solenoids when they changed from vacuum operation to 12V power.

It doesn't sound like air/fuel adjustment is your problem...at least not causing the stalling when the a/c is turned on. The adjusting screws are probably encased in plastic caps to keep people from messing with them due to emissions regs back in the day. Little things like that have the Quadrajet a bad name when it's actually an excellent carburetor. Those little caps made it difficult to tune the car for best performance as if the car was tested for emissions and those caps were gone there might be a fine involved depending on the jurisdiction.

[Avanti83]

I have an '82 with a 350 crate motor equipped with a Quadrajet carb. The engine / carb have approximmately 7,000 miles on them. Lately the engine quits running when the A/C is turned on. It also quits when doing a slow sharp turn, as when parallel parking. Both problems occur when the engine is fully warmed and idling smoothly at 750 RPM. My initial thought is that perhaps the idle mixture could be adjusted slightly richer (along with appropriate adjustment to the idle speed) to get more torque at 750 RPM. However, the idle mixture adjustment screws have oblong-shaped heads with two flats and are placed in recessed openings in the base of the carb. Is there a special tool for adjusting the idle mixture on this make / model year carburetor?

Carbs of that era were equipt with an idle control solenoid that boosts idle with the A/C on. Yours may be missing or non-functional. With the good stable idle you have, I'd check that out first before I'd adjust idle

Bob

[adamderosa]

There's a special tool to adjust those "tamper proof" idle mixture screws. It looks like a screwdriver with a special tip on it to fit those screws. Your local NAPA or other good auto parts store sould have it.

[Ray K.]

There's a special tool to adjust those "tamper proof" idle mixture screws. It looks like a screwdriver with a special tip on it to fit those screws. Your local NAPA or other good auto parts store sould have it.

Thanks, guys. I found one of those tools on-line for $18.95 + shipping. The solenoid sounds like a promising area to explore, too, only it is too hot in my garage to work in there. Might have to wait till October!!!. As a side note, I remember speaking with police officers, back in the early '80s, who said that their cruisers were wired to cut off the A/C whenever the accelerator was floored. This gave them a few more HP to catch the bad guys.