After some further testing yesterday evening, here's where I'm at today...

CIS Computer, Temp Sensor, Idle Control Valve, Throttle Microswitch all check out within spec & function as needed. The two EHAs I have are suspect, but wiring from CIS computer to plug is OK, so I decided to swap them again hoping for a change...

EHA 1 - Difficult start but car pulled strong off the line & idled around 1200-1300 rpm when warm. Constant error of 90% DC (neg on pin 2 & pos on pin 3)

EHA 2 - Car started every time to a smooth 750-800 idle, but stumbled pretty bad upon enrichment/acceleration. Once warm, would hover around 1k idle, fluctuating up and down 100 rpm. Constant error of 9.4% DC here (neg on pin 2 & pos on pin 3)

Progress... sort of. Assuming the 9% DC with EHA "2" is the 10% error (potentiometer/throttle pos switch), I swapped a new functioning replacement poetntiometer in to what I thought was within spec (.78v iirc). Idle remained around 1k rpm and no fluctuation off the 9.4% DC error.

Before I make the plunge on an EHA replacement & fuss around with throttle linkages, I want to have the X11 port show the 70% DC with key on Engine off... showing that there are no errors & allowing me to move forward with fuel adjustments.

Has anyone experienced the 10% DC error where the potentiometer was not the issue? If so, what steps were taken to correct your fault?

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1989 300 SEL - Under the knife
2003 VW GTi 20v - 3076r
1986 Chrysler Laser XT- T-top