[Hoss]

I dont want to jinx it, but I think I've figured it out.
I have had an off idle stumble for the longest time.I searched on here and every site That I could Google. I messed with everything from accelerator pump to timing to vacuum advance without result...just aggrevation.
Recently, I came across a site where a guy had a Mustang with similar symptoms. He was advised to check float level. I thought after the rebuild, mine was set properly. After "wet" adjustment, The stumble has disappeared.
Needless to say I'm happy with the Cougar again!!!

 

[cougar1]

Glad to hear it. Sometimes the simplest things go unseen or unthought of. I have a similar story with the camaro. Rebuilt the 327, everything perfect, degreed the cam and all. The car refused to idle and at one point it would not run under 2000 rpm and barely pulling any vacuum. I posted it on the camaro website and had over 1000 views. No one could figure it out. I have ase tech certifIcations and was scratching my head. Pulled the carb and could tell it was running really rich at the base where the idle screws are. Long story, the 4bbl intake on these has an exhaust passage to warm up the carb and without the heat shield plate as opposed to a regular gasket, the exhaust blows past the carb passages that run off vacuum. I was actually blowing air into the carb and throwing off the entire vacuum signal. A $5 metal gasket solved all the problems!

 

[Bad69cat]

You probably got it. 1st go through on a carb rebuild - rarely perfect. It's even a bigger pita on small engines - they can be very finicky. The floats on autolites are famous for hanging up as it is. Sometimes it's as simple as taking it off turn it upside down giver a shake and slap it back on. Small block Mopars are famous for the crossover passage under the carb to plug up with carbon and keep the choke from operating properly....almost everything has a quirk or 2. That's part of the "fun" --- right.

 

[Hoss]

The thing is...The whole time I'm thinking...I adjusted the float...it couldn't be that.

 

[Cougar_is_Grr8]

Just like when I replaced all the rubber lines on my F250 and she was running like crap. I kept thinking, but I replaced all the lines.. turns out one of them had a pinhole so it was sucking air into the fuel.

 

[Hoss]

Re: Autolite 2100 Stumble issue solved....Part II

I have to update this thread. My stumble issue returned shortly after I posted this.... I have tried everything from vaccum advance to choke,timing, and just about anything I could adjust. I was off and on obsessed with this problem.
Finally last night I Googled "off idle stumble" and about 3 pages in came upon an excellent post from Mustang Monthly Forums where a member had posted detailed photos of the booster assembly. I went out at 9:30, pulled the carb and tore it down. It turns out that there were tiny passages that even though I soaked the whole carb well, were blocked solid. After a good cleaning and blowing everything out, reinstalled it at about 11:30.
To make a long story short, the car is running so good, I'm scared to drive it waiting for the stumble.
I am very relieved to hopefully have this simple yet complicated problem solved. Thank God!....really.

 

[Bad69cat]

Glad to hear it! Those are not the easiest of carbs to rebuild in the first place, but they do run good when done right. Congrats! Now you are a pro Autolite rebuilder!

 

[jshcobra]

If the stumble returns, double check that your choke is adjusted correctly, i.e, the paper clip trick. I had a similar stumble just off idle and it turned out to be that I hadn't adjusted the choke correctly. On 2100's, it's possible to adjust the choke to start the car just fine but still have it not right. The choke piston (inside the choke housing) must be at a certain spot before any adjustments are made. Once I did that, the stumble disappeared and the car has never run better.

 

[Cougrrcj]

Glad to hear it. Sometimes the simplest things go unseen or unthought of. I have a similar story with the camaro. Rebuilt the 327, everything perfect, degreed the cam and all. The car refused to idle and at one point it would not run under 2000 rpm and barely pulling any vacuum. I posted it on the camaro website and had over 1000 views. No one could figure it out. I have ase tech certifIcations and was scratching my head. Pulled the carb and could tell it was running really rich at the base where the idle screws are. Long story, the 4bbl intake on these has an exhaust passage to warm up the carb and without the heat shield plate as opposed to a regular gasket, the exhaust blows past the carb passages that run off vacuum. I was actually blowing air into the carb and throwing off the entire vacuum signal. A $5 metal gasket solved all the problems!

BTDT with my old Camaro as well... Without the metal heatshield gasket, the crossover heat was heating the carb too much and making the gas boil in the bowl, then running like crap.

 

[Hoss]

When you have problems like this, you know its something simple. I think thats why it's so frustrating when you rack your brain, as well as everyone else and you still can't figure it out. But when you finally get it, It's such a relief and it makes you feel good.
That's probably what I enjoy about this hobby the most.