Won't idle

[rhb1999]

I have a 1981 Buick Century 4-dr. in #3 conditon, rear wheel drive, 231 Buick V-6 with a 2-barrel "DualJet" carburetor. It starts fine but quickly stalls. It just won't idle. To test whether it is the carburetor, I put on another carb from one of my other cars, and it seems to run better, to where I can drive it. Could the other carb just be dirty inside? What causes a carburetor not to be able to idle. I want to put the correct carb. back on the engine. Any information would be greatly appreciated. Thanks.

[Smartin]

Have you ever rebuilt a carb before?

Sounds like the idle circuits are clogging. Open it up, clean the parts and all the passages. Blow them out with compressed air and reassemble it.

If anything, it will confirm that your problem lies there or somewhere else, depending on if it works or not.

[JohnD1956]

If another carb seemed better, but wasn't, then you may want to look at electrical, ie plugs and wires.

How old is the gasoline? And what is the potential that the tank took on additional condensation? Have you tried doubling up on the dry gas?

Also what about dried and leaking vacumn lines?

[NTX5467]

On some of those cars back then, there was a check valve that went to the cruise control servo. It was like one line in, two lines out and was a bonded together valve of two plastic pieces about the size of a dime. With time and age, they'd crack and cause a vacuum leak.

If it works fine after you break it out of the idle system or until it comes off of fast idle, it would be an idle system issue. I'm not sure where the idle feed tubes are, but there might be an obstruction in them but would still "appear" open.

About 12 years ago, I bought a '80 Newport V-8 from a wholesaler. Problem was it ran fine but would not idle. I rebuilt the carb and cleaned it out with spray B-12 Chemtool. Everything looked to be good, but as soon as I got it started and the B-12 was depleted from the idle tubes, it died. I checked all of my Chrysler manuals for the "low speed jet" and where it was located. I finally took the venturi cluster out of the Carter 2bbl and knew which tubes were the idle tubes. I started to probe the end with a bent-wire spark plug gap gauge. The jet was recessed up in the tube a little ways, but with each probe, the hole seemed to get bigger and clearer. I bought a selection of small twist drills and used them to get a uniform size on the hole, going just until I "struck brass". Then washed everything out again and that was the end of that problem. A regular rebuild would not have fixed that one as the tubes were corroded from flaky gas out in West Texas.

One thing to investigate is whether it's not idling due to not enough fuel or if it's killing itself with excess fuel. If it's excess fuel, it could be just an air bleed in the venturi area that's clogged (causing the idle circuit to go full rich, even make gas drip from the venturi in some cases).

Might even be an egr valve that's hanging open due to deposits where it's plunger seats against the intake manifold.

Might even be a combination of things that might not be terribly hard or expensive to fix, just time consuming to track down.

Hope this helps,

NTX5467

[rhb1999]

I've rebuilt a carburetor but it's been awhile. What you said about the idle circuits being clogged up from deposits make sense. I'm going order a kit and clean and blow out them. I remember seeing in auto parts store, a gallon can of carb cleaner with a basket to submerge the float bowl. I plan on doing this too. Thanks alot!

[rhb1999]

Thanks for the information on the idle tubes/jets, I'll try this too. Thanks everyone!