I borrowed a family members 94 Legacy to fix a repeatedly dying battery. Easy fix; the 'parking lights always on' button was toggled on. However, after charging the battery the 'check engine light' came on and car was hard to start. It cranks fine but won't start on the first minute/2-3 tries; then starts, runs rough for a minute or 2--with the fan running, then runs fine.
My initial guess was a temp sensor but I just can't reconcile the coincidence of the battery being charged just before the CEL came on. No trouble codes yet. Car has about 110k miles and has been meticulessly maintained. Any help greatly appreciated.