I've got a (still) stumbling 92 Legacy. A few days ago I noticed the CEL come on for just a second and go out. Every day is worse than the last. Stumbling, shuddering, surging. Now all speeds, hot or cold.

 

Today I read in the CEL codes and got 12, 13, 14, 15, 16, 17 and 31. I cleared the memory (confirmed it), drove around the block and saw the the CEL flash on and again checked the memory and got the same exact thing. 12-17 plus 31.

 

I checked the idle control for about 10 minutes running between idle and full throttle both by checking resistance and signal voltage. I moved the throttle slowly, but everything is behaving perfectly.

 

One thing... my manual says signal voltage should be 0.5-1.0 volts with throttle closed and about 4.5 wide open. Mine reacts the exact opposite, so I'm guess that's a type. Closed 4.5 volts down to almost zero full open.

 

Any ideas? Changed air & fuel filter, PVC, plugs, cleaned MAF sensor, checked coolant temp sensor, replaces cam sensor (had a spare). O2 sensor was changed about 6 months ago before problems.

I'll beat everyone else to asking a few questions. What kind of plugs? Are the wires Subaru or other? What O2 sensor did you use (OEM or another brand)? Did these problems come up before you put all the new parts in/were you putting them in running this down? Or did the problems start after you started replacing parts? If so, which part did you work on/move/disconnect at that time?

 

Have you checked your fuses and looked at your harness? Could you have gotten rodentized?

 

Sensors, injectors... I wonder if it's a computer problem. Have you checked your electrical system for faults? I'm not really good at problems like this, but this is what I'd look at first, anyway.

I'll do you one better: I live near you. PM me and I'll give you a number to call to set up a meet.