Idle up and down

[Retroman1969]

Mine did this very thing last fall. Turned out to be bad gas. And it took awhile for it to start acting up after the fillup. The closer to empty it got, the worse the irratic idle was. Filling it with fresh gas fixed it immediately.
That may not be it, but it would be the cheapest and simplest thing to try first.

[jdraupp]

Originally Posted by Retroman1969

Mine did this very thing last fall. Turned out to be bad gas. And it took awhile for it to start acting up after the fillup. The closer to empty it got, the worse the irratic idle was. Filling it with fresh gas fixed it immediately.
That may not be it, but it would be the cheapest and simplest thing to try first.

Yep and throw some techron treatment in there on the empty tank just to try another easy fix.

[thom4782]

Classic dirty throttle body symptom

[kk2002s]

I would agree on the dirty TB (I have had the hunting idle, cleaning TB cured it) except it just started after changing the battery so I would first suspect, as mentioned, that learned memory was lost.