Eagle Won't Idle at All.

[TLC87Eagle]

Here's the story.
The engine has been rebuilt last year, ran fine and perfect.
Last month I rebuilt the carb, ran fine after that.
Took it on a 600 mile road trip last week, ran fine the whole time.
Got back home, ran fine all this week until yesterday...when I started it, it wouldn't idle at all, the engine would rock and shack very badly with RPMs dropping below 300. I've been browsing the forums and checked just about everything. The idle and RPMs come back when you close the choke plate down, which makes me think it's a vacuum leak. I've searched every line and sprayed them with carb cleaner, not a leak to be found.
Next I pulled and checked the idle tubes and jets and sprayed them out, no fix.
I checked all of the plugs, swapped the ICM, the Coil with spares just to try, no fix.
I changed the fuel filter, and PCV valve no fix.
I am now drawing a blank to what it could be.
Is there anything I am overlooking that anyone else has experienced?

A summary of what I've done thus far for those who don't like to sort those paragraphs.
-Checked for vacuum leaks with carb cleaner.
-Tightened manifold bolts
-Cleaned idle tubes
-Checked Plugs, wires, ICM, Coil.
-Changed Fuel Fiter, PCV valve, air cleaner.

Other symptoms are that the exhaust pops and smells odd. When revved up with little throttle and let off, there is a backfire like popping as RPMs come back down. Runs fine and smooth above 1000RPMs, so I have to hold my foot on the gas at lights to keep from stalling. There is run on and dieseling sometimes at shutoff. I also had some carb backfire on a few starts with the air cleaner off.

The only thing I can think of is a batch of bad gas as the exhaust doesn't smell right. So I added a bottle of HEET, and am waiting for results. Maybe it could be something that simple.

I also read on a Jeep forum that the Charcoal Evap. Canister can cause vacuum and other problems, the larger tube next to the cap on the canister has a hissing sound, but when pinched off, there is no change, other than the hissing going away. I also changed that hose yesterday.

I am just hoping it is bad gas, as I can think of anything else.
Thanks for your help in advance.

[jim]

One of mine used to do that sometimes.  It was usually because the vac hose came off the tee at the fitting on the manifold behind the carb. 

[EAGLER]

vaccum hoses tend to crack because of the heat . vaccum leak could be the guilty

[jim]

You seem to have done a good job of looking for vacuum leaks, but they can be difficult to find.

[TLC87Eagle]

Yeah, I have searched pretty thoroughly, but I will check over the hoses again tomorrow.
It does seem like a vacuum leak to me, I just can't seem to find it.
For as bad as it idles, it should be a very obvious hiss.
Maybe a T-fitting is cracked or something. I will pull some out tomorrow and check the fittings.
But I could not get a response with carb cleaner on the hoses.
Thanks for the input.

[carnuck]

Bad brake booster? Cracked vacuum ball? Got a compression tester? Water in dist cap? Could be a sticky valve (anything fall down the intake?) Marvel mystery oil in the gas can loosen stuff up too. Were any rockers clacking? Bent pushrod/broken rocker would do this. Probably worst case scenario is cam walk. Before I went to that, I would cross #1 and #6 plugwires at the cap, make it backfire a couple times with the aircleaner lid off then put them back normal.

[TLC87Eagle]

Thanks for the input guys.
I found my problem this morning.

I noticed the carb would drip gas down the to the butterflys when cracked a little open.
So I pulled the carb a little further apart and noticed some sediment from where the idle tubes pick up from.
I sprayed everything down with carb cleaner and put it back together, and it is back to normal.
I guess the plugged tubes were causing a lean condition as it would idle right when the choke plate was closed.
This made me think it was a vacuum leak as I thought plugged idle tubes cause a flooding rich mixture.
But its back to normal after cleaning the idle tubes and idle tube pick up.
But at least I know there are no vacuum leaks or ignition problems as I checked just about everything. 

Thanks your input guys, I know my way around under the hood pretty well, but this was just frustrating, and stressful when pulling up to stop lights.

Hopefully things won't plug up for a while now, but if they do, I now know what to do. 

[AMC of Houston]

There's an AMC service letter that may help with that recurring later on.   Basically says to drill out the bottom of the idle bleed tubes to 0.030 (thirty thousandths); then reset everything per the IS-2e service letter.   I've done just that on many BBD carbs, and it works as advertised!!   I can send you a scan of the IS-12 if you need a copy.

[jim]

Glad you found it.  It's satisfying to solve an issue.  In this case you did it on your own.  No one else mentioned the idle tubes, though we all should have thought of it.