Hunting at idle?

C

Cdntiger

Gold forum user
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120
Hi,
My '66 is bone stock, I don't think the motor has ever been opened.
A couple of times lately, I've pulled up to a light and the idle starts hunting up and down, sometimes to the point of the car almost stalling, even if I goose it a few times, the problem persists.
It doesn't do it every time, sometimes idles fine, the points are fresh, any ideas?

Cheers,

Paul
 
Hunting at idle

Sounds like air is getting in somewhere to alter the fuel mixture. Too strong of a throttle return spring can wear or pull the throttle shaft over time causing it to wear, giving air a place to come in. How old is the Carb? Give the throttle shaft a wiggle to see if there is any movement, it doesn't need much. If you like the Carb you can have it bored and sleeved on the throttle body, or buy a new one. Check also to see if the rubber plugs don't have any cracks. Check Carb gasket to intake and snug the bolts down or replace that gasket.

Brian
 
Small motor trick

Take a can of quick start or carb cleaner and spray around carb points of wear if the engine increases RPM you have found your leak.

Have a fire extinguisher nearby and use due caution.

How old is fuel? is contaminated with water ?

Slop in dizzy shaft?
 
I've run into this a couple of times. Typically a rolling idle is a fuel problem where extra fuel gets into the engine which causes it to start to stall; then as the vacuum drops the source of the extra fuel diminishes and it recovers. Lather, rinse, repeat.

In one case, I suspect that it was some gunk in the idle bleed screws. After resetting them several times with no improvement, I pulled them, inspected the screws and seats, and with everything looking good put them back in. Problem fixed after that, so I think there was something in there that got flushed out.

In another case, the power valve had loosened slightly and was leaking fuel past the gasket. A quick check for this is to let the car sit overnight then pop off the choke plate and see if there is still fuel in the bowl. If not, chances are it leaked past the power valve gasket. I also made a tool that allows me to check the power valve (for a blown out diaphragm) with the car running. It's just a bent wire that can reach below the float and actuate the valve.
 
Thanks for the tips guys.
Had it out again yesterday and it ran fine with no issues, so maybe intermittent vacuum leak, or I would think most likely in my case, minor issue with the 2100.
I'll take a look today to see if I can find anything.

Cheers,

Paul
 
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