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.

[rjames]

So you can drive the car, but it idles high and then will eventually stall?

As has been stated, with Djet, a vacuum leak will lead to a high idle, but won't cause it to stall. I wonder if at idle if the engine is not getting enough fuel or too much fuel. How do the plugs look?

Instead of just swapping out the throttle body without verifying if it's bad, I would do a smoke test and verify that there is indeed a significant vacuum leak and where it's at. Undoubtedly the throttle body will be leaking a little (they all do at this point unless rebuilt), but the airbox is prone to rusting out from the inside and could be a culprit. A homemade smoke machine can be made for the cost of an empty jar, some tubing, and epoxy to seal it all up.

In addition to a possible vacuum leak, I'm wondering if the ECU is not sending the correct signals to the injectors, which could account for why it's stalling.

I chased my tail for months trying to figure out why my car would run great but would intermittently stall at idle (rarely in the driveway, but usually when out on the road). Turned out the ECU was bad and would intermittently cause a full rich condition.

I'm not one for just swapping parts out randomly, but the ECU is something to consider.