Rebuilt 12a with 40k and orig carb etc. Checked solonoids and vacuum lines(I think). Also checked throttle opener and adjusted. Had compression test and have replaced intake manifold gasket. Car runs smoothly with choke engaged and when warm I can adjust down to around 1200 Rpm car seems to hunt for Idle between 1000 and 1200rpm but it just won't drop below that(stalls) Car sat a long time before I purchased it, and carb itself is in unknown condition(other than well cleaned with carb cleaner from top) I plan on making alterations to car later, (like new carb) but want to be sure everything else is ok. I wouldnt trust myself to do a complete rebuild, but would disassemble top portion of carb if necessary to clean jets etc. I would appreciate any suggestions.

 

how does the car run otherwise?

if i'm getting what you're saying, then it will idle, but searches between 1000 and 1200 RPM, right? however, when you try to set it lower, then it will stall out ... well, i can't think of why a carbed car would search, but before totally condemning the carbie, i'd definitely start with checking for vacuum leaks again, and also checking the timing.

 

believe it or not, a car with the idle screw turned too high will sometimes search, pulsing to higher RPMs in an effort to find that lower 800 RPM range. Strange but true.

However, yours only wants to idle when rich. My friend's Honda Civic (1987, and yes it's carb'd) does the same when cold, especially winter cold. How cold is it in Indiana? (I've no idea)

 

Did you replace that blasted rubber hose at the rear bottom of the carb intake manifold? (Air Control Valve isn't it?), its the one that always splits and then your car won't idle or run right. (3/4 inch rubber hose or so.)

Also, check the blasted dad gummed shutter valve, as that one will definately cause a bypass vacuum leak. It is the 1/2 inch hose that runs from your air cleaner to the shutter valve diaphragm at the base of the carb, driver's side rear. Pull the top off your air cleaner, stick your finger over the hole for that hose, and if you feel any suction at all, then its shot. Best thing to do is plug that hose. (Actually, do it anyway!)

 

Thanks for the advice. The Idle screw just adjusts throttle it is not a rich/lean mixture screw. After I get the engine warmed up, the car runs fine- I hve been trying to back off the Idle screw until I get the Idle to 700-800 rpm. but when it gets down to 1200 it starts dropping off(between 1000 and 1200) It sounds like the car starts to die- vacuum drops- Idle picks up -Vacuum increases and Idle drops off. the timing is close (I can't set it exactly cause Haines says to set it with Idle at 800 rpm),and plugs and wires are replaced. I'm going to recheck vacuum lines, I have looked at the air controle valve hose and it isnt cracked, but does seem to fit loosely and may still be leaking a little. I will also check the shutter valve hose for vacuum and plug it. the only way I know to check vacuum leaks is to listen or spray with carb cleaner and listen for engine to rev.
Thanks for the help I will let everyone know what I find.

 

well, good luck and yes, do let us know how everything works out. however, i'm not sure, based on what you said, if you realize that there are 2 screws for the idle. one for setting the speed and the other for the mixture ... if you already knew that, then i apologize.

 

Thhanks for the tip on Idle screws I will refer to manual again, but I thought the only way to adjust Idle on 8412a carb was the screw under the throttle cables HTe other mixture screw isnt visible(I think it has some kind of cap on it), and thought I read it shouldn't be adjusted except by dealer- Is that just because of emissions? also any advice on how or which way to adjust it(as well as how to take the cap off- i have both Haines and Chiltons to reference. Thanks again.

 

dude, that's funny! kinda reminds of that stuff about "these parts are meant for race cars only which may never be used on the highway" ...

anyway, i just used pliers and pulled the cap off. you can adjust it yourself. i believe counterclockwise is LEAN and clockwise is RICH ... HOWEVER, i also believe that you should NOT go mucking with it until you've exhausted all other options. throwing it off may just complicate and compound your problem - especially since it sounds like you've never done it before.

 

Just the opposite. Clockwise is lean and counter is richer. Do the procedure just like the book says and its all mighty fine. But, since you can't set an initial idle, I'd just screw it clockwise untill it gently seats, counting the number of turns it takes. (Write it down). Set it back out three turns for an initial setting.

I'm still betting its your shutter valve giving you a vacuum leak.

 

I'll find out where it is set first by counting the turns in. then go from there. Thanks for your help. I'll include a pic with the next post, so youll know why I'm trying to save a buck! thanks!

 

It was the shutter valve. still not a perfect Idle but much better, I plugged the hose. Thanks everyone