LeBaron Idle hesitation

What's wrong is that you've now got the vacuum advance connected to un-ported vacuum. Put it back on the port that originally had OSAC- you should see vacuum on that port ONLY with the throttle opened somewhat.

Set the timing as follows:

DISCONNECT the vacuum advance line. Set base idle timing to whatever the sticker says (usually TDC or 5 BTDC for a 318) at about 700 rpm (or whatever the sticker says0. Then hook up the vacuum advance. THEN set the idle speed.

Thanks for the post Steve

I reattached the vacuum line to the OSAC port. no vacuum up to 2500 RPM, as measured with a vacuum guage. Set RPM per label, 730 RPM, Set timing per label, 12 BTC. No idle problem, and thats good, pickup is a little better. Dist timing doesn't change till about 1300RPM then only about 8-10 degrees. Never see anything from the ported vacuum outlet. Is a carb rebuild in order at this point?

It may be a plugged ported vacuum passage. I'm not sure a total carb rebuild is in order. Try flushing out the fitting with a spray can of carb cleaner. If you can see the cleaner squirting in the throat of the carb, the passage is open. Is the vacuum advance can diaphragm intact? Test it by applying vacuum to the hose (suck on it, if you're not afraid of the taste of gas fumes, use a hand vacuum pump otherwise ;-) and see if it HOLDS vacuum. It might be leaking and still be able to apply advance when hooked to straight manifold vacuum. The ported vacuum signal is usually weaker and might not be able to "keep up" with a leaky diaphragm.

Could be that. Could also be an incorrect carb gasket (between body castings or between the throttle body and the manifold) blocking off the passage that's suppose to supply vacuum to the spark advance port. Could also be one of the many boneheaded "engineering changes" (hacks) one finds in "remanufactured" carburetors. Bowl vents crudely disabled, linkages crudely rerouted, passages plugged off with ball bearings driven in, etc.

DS

I know for a FACT that using the wrong carb base-to-manifold gasket with a 2-bbl Carter (this is an 80s LeBaron, after all) will block ONE of the vacuum ports. The problem is that I've been away from 2-bbl carbs so long now that I can't remember for sure if its the manifold vacuum port (I think it is) or the throttle vacuum port. But my vague recollection is that the throttle (ported) vacuum nipple on those carbs is just connected via a straight passage into a slot in the venturi wall right above the throttle blades- no gasket. But still, incorrect gaskets are a good thing to check.

There's always THAT possibility too, but I didn't really want to jump straight there from the get-go :-/

Plugged it is. Tried carb cleaner, no go. Tried compressed air, no go. Tried a 26 AWG wire, dead end about 1 1/4 inches in (I know, never stick sharp objects in carb passages, it was copper, it was soft).

The opening is supposed to be above the throttle plate, according to the manaul. And yes, this is a rebuilt from "Auto-Line" (was on car when I got it). Thinking of taking the carb apart and checking for wrong gasket, as suggested. The manaul's, cross section drawing doesn't show where this passage actually is supposed to go. I'll check the venturi just above the throttle plate as mentioned in the post.

Thanks for all the help.

What fun. Now you get to try and figure out where the obstruction is and how to clear it!

Urg. Good luck to you.

Good plan. Get a good quality carburetor kit (e.g. Standard Hygrade).

Which manual are you using?

Just had another thought, and Dan you'll have to supply more info here. I've lost track of whether this was originally a computer-controlled feedback carb car or not. I know that its now running a standard distributor so its at least had the ignition converted. My question is, did the feedback carbs have the standard ported vacuum outlet? Or was it blocked and only manifold vacuum sent to the transducer mounted on the computer? Could this be a carb intended for use in a feedback system?

My brain hurts- peopl in my family have owned several of those cars, but its been so long ago now that I just don't remember details like that. I do remember the issue of a Carter 2-bbl needing a different base gasket than an otherwise identical application Holley (the Holley gasket blocks a port on the Carter carb)... but not the more subtle differences of feedback vs non-feedback versions of the carb.

An '80? Pretty sure (but not 100%) that Feedback with O2 sensor didn't start til '81.

Ooh, good question. Generally, the carbs that did not have a distributor vacuum source on the inside -- didn't have a distributor vacuum nipple on the outside!

There are some experiences so hellish that the human brain blots them out in a desperate attempt to maintain sanity ;-)

No, O2 sensor. The current installed carb has no wires coming out of it for computer controls. Factory service manual is from 1975, but all the wiring and hose locations, appear to be the same as whats in the car (less the missing lean burn system). If this carb was intended for a lean burn system, then I would think this port would be blocked. By the way, this vehicle was serviced only by a Chrysler dealer. I saw the paper work for it. They actually rebuilt (or contracted out) the engine rebuild about 10,000 miles ago. They would have been the ones that dumped the lean burn system. There are two externally blocked manifold vacuum ports (and yes they are functional). If I attach the dist to one of these ports the advance jumps up to 23 degrees. I have a spare carb for my 360, will it work on this 318, I guess specifically, is the manifold bolt pattern the same.

OK, just dismantled the carb. The OSAC orifice goes down to the bottom plate that has the throttle plates in it. It passes through the gasket, into a small (about 1/8 x 3/16 x 1/4 deep) cavitty. The cavity has no exit. Nothing is blocked, there just isn't an exit from this cavity. Even the gasket is solid around the hole. Almost like the factory forgot to drill the hole into the venturi.

So, seeing as blocked is the normal condition, I figure a 1/16 th drill bit might solve my problem. Worse case, I can always block it again.

Any ideas on a hole size for this port??

Eeek. Get a correct-year FSM. So many little details changed in the vacuum system, carburetor, etc. that using a '75 book is *almost* worse than using a Chilton, Haynes or no book at all.

Your 1980 car could very easily have been set up for manifold vacuum spark advance right from the factory. It is a common but mistaken belief that the spark advance port was always above the throttle plate at its idle position.

Yes, the bolt pattern is the same.

The "moat" around the throttle bores, yes. That means this carb was set up for manifold vacuum spark advance, *not* ported.

It's not supposed to. Vacuum is supplied to the moat via notches in the carb-to-manifold gasket. The correct gasket looks like this:

DS

AH, gotchya. Sorry, you were probably talking about a mating face between the fuel bowl/venturi casting and the throttle body casting.

Tells us this carb is equipped with a throttle body originally set up for no-vacuum-advance operation, as found on vehicles originally equipped with ESA (Chrysler's Electronic Spark Advance). And that, in turn, tells us a really old and yucky story about "remanufactured" carburetors. :-(

Mixed-and-matched carburetor castings. "Remanufactured".

Ding.

Well, "supposed to"? You've already gone to a vacuum advance distributor, so you need a carb that'll operate such a distributor correctly. One like this:

Well, in this case it was a "yes and no."

Yes, every time I opened the hood on that gray shoebox of an 83 Gran Fury, the mere sight of the sphagetti bowl of vacuum hoses caused me a bout of acid reflux mixed with nausea.

On the other hand, the damn thing just ran, and ran, and ran, and ran, and ran, and ran, and ran. Right up to over 200,000 miles, and no one ever had to get deeper into the carb than changing the air filter. And for that I'm eternally grateful, because I'm sure my language would have turned the air 3 shades of blue if I'd been the one having to fiddle with it... ;-) I learned the Holley vs. Carter base gasket difference on a buddy's '84 pickup, but that was a non-computer non-feedback application even as late as 84.

Well, I'm going to agree with Dan and say that an '80 was probably not a feedback carb. But even if it WAS a computer-controlled application, they did still have a vacuum advance signal that was fed to a transducer mounted on the control computer. I just can't remember if that transducer received the same (ported) vaccuum signal as a conventional distributor, or if it received manifold vacuum. Theoretically, the computer could use either one so long as the software "knows" what its looking at.

In general, carbs do swap between a 318 and 360 if they have the same number of barrels. Just watch out for the base gasket difference if one's a Carter and the other's a Holley. Also the air-cleaner throat opening may be a different size. Some 2-bbls used a larger air horn- maybe even the same size as a 4-bbl, but I think there was an intermediate size as well.

I think you hit the nail on the head

My experience is that 318s set up for manifold vacuum advance run like cr*p. You have to close the throttle so much to get a decent low-speed idle that they're idling on just a whiff of air/fuel, so the idle is rough and torque-less (the AC engaging will drag it down enormously, for example.) Also the off-idle response is *terrible* because the minute you open the throttle a crack, the manifold vacuum staggers, the advance disappears, and there's a huge transient until everything settles down in a higher air-flow/less advance state. Which is pretty much the symptom you described at the start of this thread. So even if the car was "intended" for manifold advance, I'd take the opportunity to convert it over to ported advance so that it'll actually run well.

Would have been manifold vacuum. Doubt it had a feedback carburetor unless (possibly) it was California spec.