The 98 OBS 2.2 I picked up had an idle that was not as smooth as a Subaru should be. The normal stuff was done, new plugs, plug wires, cleaned the intake track with Seafoam.

 

It was still a little off. I went to jump a car the other day and was shocked at the amount of corrosion under the positive red boot.

 

I took some time to neturalize the acid and clean everything up. The idle is now as smooth as can be. Just a reminder that the ECU and sensors are operating on very small voltage signals and need a good clean circuit.

 

Hope this helps someone down the line.

Thanks for the tip Imdew. Bad connections like that to the battery can let noise through since the battery acts somewhat like a filter for the electrical system. Another good reason to keep those battery connections in good shape.

Cool. Maybe it also had to do with resetting the ECU? I saw an article on EndWrench, forgot the years impacted, where if the battery was previously disconnected for only a short period of time and reconnected it could have a poor idle?

[...]I saw an article on EndWrench, forgot the years impacted, where if the battery was previously disconnected for only a short period of time and reconnected it could have a poor idle?

http://endwrench.com/images/pdfs/RoughIdle.pdf

I know the disconnect of the battery will cause the ECU reset. The info I was passing on is that the poor idle was before the battery was disconnected not after. Cleaning the terminals fixed the problem! Larry