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.

[emerygt350]

That's what I was thinking too. Although it seems to be too rich at hot as well, not going lean. Verify the mps and ECU are correct for 73 and matching while you are in there. Until those are known, the TPS is set correctly, and you get the right cht and ballast resistor, I wouldn't mess with anything else.

[Superhawk996]

That's what I was thinking too. Although it seems to be too rich at hot as well, not going lean.

Good point but:

1) I guess I’m not sure what his actual operating temp is and how much “leanness” as a percentage of what he’d actually be getting without the 270 ohm ballast resistor in place.

2) I ASSUME ( (IMG:style_emoticons/default/chair.gif) ) there is also some interplay in the 73 MPS & 73’ 1.7L/2.0L common ECU that also enriches the mixture via the unique 037 MPS in order to be used with the 2.0L. Said a little differently, I don’t think it was only the 73’ unique CHT + ballast resistor combo that was responsible for “extra” enrichment for the 2.0L. Anders and/or Dr. D-jet cover this somewhere on their sites. I have not personally deep dived the details here so I could be wrong.

I also think that if the TPS isn’t indicating idle state at closed throttle, that could be adding to the “richness” uncertainty.

I just know the 73’ is a bit unique and I’ve only had success with a matched 73’ system. Someday I really need to think about getting all the 74’ stuff to escape the 73’ parts that are getting rare. Or more likely, just go Megasquirt.