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]

Last I knew the engine had little vacuum across the board and dropping at idle. Timing affects vacuum, that is why I am always pestering you for those two bits of information.

[Superhawk996]

Last I knew the engine had little vacuum across the board and dropping at idle. Timing affects vacuum, that is why I am always pestering you for those two bits of information.

In the interest of extending this thread. (IMG:style_emoticons/default/av-943.gif)

In re-reading - recall his vacuum gauge wasn’t accurate. I’m not sure that ever got resolved.

Too many assumptions . . . At least on my part.

Here’s the thing - timing may keep vacuum from reaching something like 17-20” Hg but it’s not going to account for vacuum down at 8” Hg which was what was reported early on but with the questionable gauge? (IMG:style_emoticons/default/confused24.gif)

[emerygt350]

Last I knew the engine had little vacuum across the board and dropping at idle. Timing affects vacuum, that is why I am always pestering you for those two bits of information.

In the interest of extending this thread. (IMG:style_emoticons/default/av-943.gif)

In re-reading - recall his vacuum gauge wasn’t accurate. I’m not sure that ever got resolved.

Too many assumptions . . . At least on my part.

Here’s the thing - timing may keep vacuum from reaching something like 17-20” Hg but it’s not going to account for vacuum down at 8” Hg which was what was reported early on but with the questionable gauge? (IMG:style_emoticons/default/confused24.gif)

I suspect it's still a valve/timing combo. Incredibly off spark timing and valves in combination. The micro squirt won't help any of that.

[Superhawk996]

I suspect it's still a valve/timing combo. Incredibly off spark timing and valves in combination. The micro squirt won't help any of that.

(IMG:style_emoticons/default/agree.gif)

The only thing the microsquirt gets is control over a cam that won’t work with d-jet.

The thing is even some of the most aggressive cams with huge overlap still wouldn’t account for 7-8” Hg of vacuum at idle. Hard to believe that would be in his case unless the builder was incompetent. I’m not even sure if a cam that aggressive is even commercially available for the T4 engine. Again - that comment is predicated upon an assumption that 7-8” Hg was an accurate reading so who knows.