307 olds - stalls in gear

Hey all! Hope to tap in to some of the vast carb knowledge here. Much appreciate any thoughts on my situation.

I have an 87 Caprice with a 307 Olds (Canadian car) that has a 4bbl on top - believe it to be a quadrajet. Tranny is an auto 200-4r. Replaced all belt driven accessories when I bought it last week and it was running great. Last night it started to idle very low at red lights. Drop it in neutral and the idle picked back up to normal.

Got a bit worse throughout the night in city driving, to the point where it stalled a few times. After stalling, you can turn the key for quite a while before it starts again. However, 3-4 WOT thottle pumps and then turning the key makes her fire right back up.

So - sounds like a fuel issue to me. New mech. fuel pump this morning and a new filter. No change. Still idles way down when in put in gear. Sometimes it stalls, sometimes not. If it idles way down and doesn't stall, and the light turns green, it hesitates when you get back on the gas for a few seconds before taking off.

Everything above the idle circuit is just peachy. I have limited knowledge of carbs, and this is a mystery to me.

So what to tackle next?
Carb kit?
Vacuum leak?

Thoughts?

I should add, I do no beleive it to be a break booster issue, as sitting in Park with the brake hard down has no impact on the idle. Only being in gear does.

start by looking for a vacuum leak maybe you upset a vacuum hose when you replaced the drive belts ....ted

You might just want to replace all of your vacuum lines anyway. If they are hard at all anyway. Hard rubber lines means possible cracks .

Like Ted said though, check them to see if you might have had one (or more) come loose. Be sure to check the ones at the base of the carb real good.

Thanks guys. Could a vacuum leak cause my issue? I was looking and can hear a hiss, but it sounds more like it is coming from the throats of the carb than a line...

Just got back in, and all lines look good. None are hard or have the slightest sign of cracking. There are two that are blocked off by screws over on top of the drivers inner fender. They go back to a T off the intake manifold directly in front of the distributor. Other ideas? Appreciate your input :)

go to home depot and get a cheap propane torch unscrew the end tip and get a 3 ft piece of hose that slips tightly over the end start up the eng get it up to opp. temp at idle turn on the propane (don't light it ) take the end of the hose and move around the carb intake and hoses if you hear the idle increase you found the leak every body that messes with cars should have one of these in there is alot of things you will use it for like doing tune up and carb. diagnoses ....ted

Ted's propane check for a vacuum leak is first. If you don't find a leak look at your carb linkage and see if you a vacuum dashpot on the idle stop, or an idle stop solenoid that pulls in to boost idle under certain conditions, like with AC operating.

You can do the wame thing with a can of starting fluid. Either way, keep a fire extinguisher handy.

Also check the choke pull off. Notorious for being a "hidden" failure.