Still need help tuning a 32 adfa

[anothersteveg]

Hi All. Try as I might, I'm still having a problem getting my '77 tuned correctly. I cleaned the carb, new gaskets, blew out all the ports numerous times. I have removed the emissions stuff and plugged all the lines. The hoses are all new, the fuel pump is good, and filter is new. I capped off the brake booster and it made no difference so I think it's good. The idle jet tests fine and I have the choke set and working properly.

When I start it cold it fires right up and runs good until warm. When it warms up the idle is erratic, about 800-1200 rpm. I've followed the guide for tuning it but no luck. The idle speed screw seems to work as I can adjust the above fluctuation up and down, but it still fluctuates. I can adjust the idle mixture screw and kill the engine but that's about it, there is no difference backing it off 1 turn vs. 3 turns.

I have sprayed all over with carb cleaner and can't detect any change unless I spray it directly in the air cleaner.

The timing jumps between 5 and 10 degrees with the fluctuations in engine speed? The plugs, wires, cap, rotor, points, and condenser are all new and I converted to a single point system. I did a compression check cold, and all the reading were within 10psi of each other (125-135).

I've gone through as many threads as I can find in here and still can't seem to get this figured out. It was previously suggested on here to change the idle jet. I haven't tried it yet because it feels like I'm just throwing parts at it, but maybe? Also, the idle mixture screw is the original and the head is slightly bent. It threads fine though so?

I've been working on this for awhile and am out of ideas. I've tracked down numerous issues with your help and it is running much better, but still not dialed in.

[131]

What size is the idle jet? You should be able to increase and reduce idle speed with the idle mixture screw, with a sweet spot 1-2 turns out, if you can't it could be the wrong size jet.
But if the ignition advance is jumping around 5-10 deg, it may be an ignition problem and not carb at all. You can lock up the advance weights with a rubber band to take them out of the equation, just don't forget to take them off when you're done. Are you using vacuum advance? If yes, isolate that and see how the idle adjustment goes.

[anothersteveg]

The jets are stock and what the specs called for. I had to put a slightly different emulsion tube in, one from a '76 but I don't think it would make that much of a difference. Whether I back the idle mixture screw out one turn or 3 makes no difference in the idle. If I screw it all the way in it will kill the engine, but beyond that it seems to make no difference.

I have the mechanical advance distributor, no vacuum. I've never dealt with one before and was wondering about the springs. Is there a way to check and see if that is contributing to the problem? I was thinking all along that it's some kind of vacuum leak because when I spray cleaner in the intake it raises and smoothes out the idle.

Thanks for the suggestions, keep 'me coming!

[131]

I have the mechanical advance distributor, no vacuum. I've never dealt with one before and was wondering about the springs. Is there a way to check and see if that is contributing to the problem? I was thinking all along that it's some kind of vacuum leak because when I spray cleaner in the intake it raises and smoothes out the idle.

Rubber bands hold the weights and stop the spark being advanced. If you spray stuff in the intake and idle improves it would indicate richening a lean idle.

[anothersteveg]

So I took it apart and found this



I went and bought a spring to replace the bottom one and it is much better. I was able to tune the carb with the mixture now. I still don't have it 100% but I think I'm almost there.

Thanks 131!

[majicwrench]

Obviously, if you spray carb cleaner and it gets better, the advance springs are not causing problem.
Many times when doing the carb cleaner spraying thing, enough fumes get sucked into carb to raise/smooth the idle, even if no vac leak exists. I would suspect you idle mix is somewhat plugged. With car idling, slowly lower had over carb. Does it get better??
Keith

[131]

I went and bought a spring to replace the bottom one and it is much better. I was able to tune the carb with the mixture now.

What spring did you replace it with? If it's not another spring out of a Fiat distributor your advance curve will be all wrong.

[anothersteveg]

Yes I was afraid of that. The spring I had was close, but after driving it I can tell it's still off. The car idles fine but the advance is slow and it lacks power. When the spring opens I can feel the advance kick in, but it's off.

So next question: Where can I get a spring for this? Anyone have any ideas? I really don't want to buy another distributor.

[twblanset]

Did you check your idle solenoid? It could be you are idling on your main circuit. If you apply 12 volts to the terminal on the end you should hear a click.

[anothersteveg]

Ok, update: After reading some related threads and a little google research, I went and bought the kit GM makes from my local O'Reilly's. I used 2 of the springs in that kit (the black ones) and reset the timing. It runs better than ever now. After a short drive, I'm happy. It's a much better power curve now. It may not be what Fiat intended, but I'm happy with how it runs finally. I tweaked the mixture and idle a bit and think its just about as good as I can get it. I'll see how it starts cold when I get home again next week.

Thanks for the suggestions and prior threads. If 131 hadn't jumped in and mentioned the springs I'd still be pulling my hair out!