I am unable to get my car to idle under 1000/1100 rpms. Didn’t have this issue before installing the 123 distributor. Other than that it runs great but I’d like the car to be idling at 800-900rpm.
I’ve tried using both the retard and advance only curves. No difference.
I have the TB idle screw all the way in and have verified no vacuum leaks and correct timing.

I’ve seen a couple posts by others who said they also had higher idles after installing the 123 distributor. Wondering how common it really is.

I have the same issue and finally resorted to deleting the vacuum advance. It runs "ok" at idle, really well under acceleration but it runs horribly under a constant load, I just haven't spent enough time sorting the issue. Let us know if you figure out a fix.

I have the 123 with Weber’s and don’t have this problem. However I believe the only way the 123 could raise the idle is if the timing at idle is more advanced than your old distributor. If the idle timing is the same for both distributors then I don’t see how the 123 is the issue.

My 123 actually solved my hanging idle issues from the old worn distributor. Make sure you plug the port on the throttle body for either the advance or retard, whichever you are not using. Next, go back and re-check your timing advance. If the timing is too far advanced you will have a high idle. The fact you have totally closed your air bleed screw and still have a high idle leaves me to think you are either getting air below the throttle plate from somewhere else, or your advance is set too far.
Either of these possible? Just spit-balling / trying to help.

Appreciate all the replies so far. Both the retard and advance ports are plugged on the throttle body. I was using the retard port and associated curve (B) before, but same result. I was surprised that leaving the retard port on the tb open to the air or plugging it up didn’t have any effect on the idle speed. I assumed when I blocked it off that the idle would drop some. Go ahead, tell me I have a vacuum leak again. :/
I’ve also checked the timing multiple times.

Can changing the MPS settings affect idle?

So... what exactly changed other than the distributor since the problem wasn't there. MPS settings affect AFR which absolutely can impact idle. Little to no impact on idle speed by the air bypass screw can indicate a lean condition....

Share what else changed....

I reread my troubleshooting thread I posted here a few months ago. Issue started as an unstable idle and eventually the car wouldn’t start. Traced the problems to a leaking MPS and a leaking distributor dashpot. Replaced the distributor with a the 123 unit and got a replacement mps that was calibrated to factory specs. Replaced all the vacuum hoses, seals, throttle body, plenum gaskets, rebuilt the injectors and when everything was back together the car was running great and idling at 800 or 900rpm (with the tb bleed screw all the way in.)

Then I looked at the AFR readings and found the it was running way too lean. I adjusted the MPS accordingly. sometime after I got it dialed in (a couple of weeks?) the idle wouldn’t always come down to 900 when stopping at a light as it had been. Sometimes it would only drop to 1200-1500 rpms. I thought I had traced the issue to a leaky decel valve (fix one thing and another things breaks). The decel valve wasn’t closing consistently, leaving the car to idle high unless I blipped the throttle. I finally removed it from the system. It helped bring the idle rpms consistently down to 1100, but not all the way down to 800-900 as it should be.

AFR shows ~12.9 at idle.

Have the 123 ign on a 2056 with d-jet.

Also experience a high warm idle. 1100+ but still was tuning after installing it.

I've just gotten used to it. The upside is now it WILL idle cold. and I mean 40 deg cold. Before I would have to pull it out of the garage and either drive right off or shut it off while I close the garage doors etc. then restart. Now I can walk away and it will keep running. idle then is around 8-900.

Might try to close the hoses to the AAR and decal valve to see if that affects anything.

I believe that this Raby 9590 cam tends to want to idle higher anyways.
And when tuning it with the Inova timing light that displays the rpm with a digital readout, it seems that the in dash tach reads about 100 rpm high

1100 or so sitting at a light isn't really a screaming high idle. so like I said, I've gotten used to it.

it does take a bit if trial and error to get it dialed in, partly due to the sensitivity of the 123. before with my OEM distributor you had to move it further, but the 123 is very touchy that way. fuel pressure can play a roll as well - I have an in-line pressure gauge and I am right at 28-29.
also yes the Mps makes a huge difference. I have found with D-jet that most MPS for my car, if tuned to factor spec, I have 3 now, all of them had to be retuned to my car and made more rich, they all ran lean and with that had a higher idle,
but I now have a perfect 950 idle when warmed up. Please note that different people have different issues and use different settings, but on mine I am using the vac port, and with out it I would have a 1500+rpm idle! but with the vac port hooked up it pulls it right down to normal idle, and that was after doing the whole, initial set up static timing, then blocking everything and setting timing at 3500rpm, 27' btdc,
etc etc, and then with vac port hooked up its right where I want it. now I did also have to turn the idle setting on the ECU over a bit and the idle screw is closed. but Its running really good, my only issue is my AFR says my idle A/F mix is about 10.5, so on the rich side but on the road its perfect so I am not going to mess with the MPS at this point as its at 12.7 on WOT and cruising its about 13.7. head temps and oil temps are perfect. I don't see how some people are running with out the vac advance disconnected and blocked off, but I guess whatever works for you.

Phil

Be aware that there are different types of vacuum. Manifold and ported. Be sure to use ported for advance vacuum.

To me it sounds like there is still an issue. I'd make sure the AFR is right and compression and valve are to spec. Otherwise....chase your tail time.