D-jet idle and lean issues. Options

[Literati914]

1.7 w/ original D-jet.

I have the idle screw on the TB cranked all the way down/closed (which doesn't seem right tbh) and the car's idleing around 900rpm - which is within the recommended 850+/- , and the idle does not really "surge" too much but is not necessarily rock steady either. I'm also getting a steady 16.5 A/F on my gauge during idle and warm driving. So too lean. BTW, the CHT gauge has never gotten over 300 so it's not trying to over heat.

I'll be spraying the vacuum connections to see if I can find leaks - but other than that, what would be the most obvious culprit(s)?

My theory is that the idle screw needing to be closed (for a reasonable idle) is just combating say, a bad AAR or something. Sound logical? What tests can I do to the AAR or other items to look at first?

[JeffBowlsby]

A reminder that the ECU idle mixture knob is only active when the TPS is correctly calibrated. Two of the circuits in the TPS are a switch that tells the ECU to control mixture at idle, and you should see a difference in the lean/rich condition at idle under that condition. Off idle, the TPS turns off the ECU-controlled idle mixture function, and directs the other sensors combined (MPS, TS1, TS2) to control mixture as determined by the monitored engine conditions.

If there is no reaction from the ECU knob at idle, then the TPS is likely not calibrated correctly.