Idle adjustment question, Idles high or slowly stalls Options

[BillC]

I have an idle adjustment question for all you D-Jet gurus:

I can adjust the idle air screw on the throttle body so the car idles at 1600 RPM, and it will happily idle at 1600 all day long. If I turn in the screw just a little bit, like 1/4 turn, the car will slowly drop idle speed down slower and slower until it stalls. I can blip the throttle to keep it running, but it just wants to slow down and stall. This is all when the car is fully warmed up.

How do I get the car to idle steady around 1000-1200 RPM? 1600 is just too high.

Car is a '73 2.0 with factory D-Jet. I installed new Standard Products FJ67 injectors, and the fuel pressure is 29 psi. There are no leaks in the intake side, and the idle adjustment screw is about 2 turns out (so there's plenty of adjustment available in both directions). The MPS hasn't been messed with, and the ECU looks like the correct unit. All new vacuum lines, fuel lines, pump & filter, and fresh gas. New @JeffBowlsby engine and alternator wiring harnesses.

Known issues: it has the wrong CHT sensor (it's the one that's commonly available) and I think the TPS board has worn traces. I finally found the right CHT and ballast resistor, and I also have a 914Rubber replacement TPS board, and I will install both of them when I get a chance. However, I don't think either of those should keep it from idling at a reasonable RPM.

[rhodyguy]

Have you closely examined the stacked elbow? The smallest of cracks, that like to hide, can produce a high and unadjustable idle speed.

[BillC]

Have you closely examined the stacked elbow? The smallest of cracks, that like to hide, can produce a high and unadjustable idle speed.

The stacked elbow is new, from 914Rubber. I replaced all the vacuum lines and fittings, as well as all gaskets, with new ones. I also made sure there were no rust (or other) holes in the intake manifold.

Put the dizzy on 1 but don't bother hooking up the advance. Disconnect all vacuum hoses and plug them. Put the mighty vac on the mps. Give the mps 17-20 inhg. If the idle is still high, retard the timing and see what happens.

I'll give it a try next time I have a chance. However, it's a pain to change settings on the distributor, since it means pulling it out and then checking/adjusting the advance afterward.

[emerygt350]

Have you closely examined the stacked elbow? The smallest of cracks, that like to hide, can produce a high and unadjustable idle speed.

The stacked elbow is new, from 914Rubber. I replaced all the vacuum lines and fittings, as well as all gaskets, with new ones. I also made sure there were no rust (or other) holes in the intake manifold.

Put the dizzy on 1 but don't bother hooking up the advance. Disconnect all vacuum hoses and plug them. Put the mighty vac on the mps. Give the mps 17-20 inhg. If the idle is still high, retard the timing and see what happens.

I'll give it a try next time I have a chance. However, it's a pain to change settings on the distributor, since it means pulling it out and then checking/adjusting the advance afterward.

Switching to 1 isn't crucial, just better in case you want advance. You don't want retard. It just doesn't work on the 123. The dizzy is set to turn on at some small level of vacuum where the original was meant to be much more analog.

I have mine set so I can access the pot with the dizzy in the car. I use a little mirror on a stick. Super easy. If your dizzys vacuum port is pointing towards cylinder 1ish you can do it no problem.