OK, I built the code reader and spent some quality time under the hood this evening. Oh, also verified that OVP relay is current part number. No Joplin needed here.

Pin 8: codes 4, 13
Pin 14: code 11

This car is a 1993 49 state model. It does not have a CE/MIL light, does not have a built in DM LED/pushbutton, and pin 3 of the 16 pin connector is empty. So I'm assuming it doesn't have the diagnostic module functionality...

I cleared codes and reset adaptation values. Took car for a 10 minute spin. Ran great for the first 9 minutes . Then all the same symptoms returned: intermittent wandering idle (500 - 1100 RPM), surging at cruise, and a hesitation when first tipping into the throttle. Pulled codes again after drive testing and got:

Pin 8: codes 4, 13
Pin 14: clean

Not quite sure how to proceed from here. Thinking my best bet is to go hunting for vacuum leaks and fuel pressure problems.

This car has a newish wiring harness. No record of O2 or MAF replacement. If I cannot find a vacuum leak perhaps a fresh O2 sensor is the next step? I'm open to suggestions.

- JimY

ps: Just thought of this tidbit. The car always run fine for the first minute when started cold. I assume this means it's OK while in open loop mode, and it only misbehaves after switching to closed loop. But does this indight the O2 sensor, MAF, neither, or both?