Surge underload and knock sensor code fixed

[bikes1]

2004 base Vibe, manual transmission, 210,000 km.

I bought my Vibe about 2 1/2 years ago with 130,000 km and it's always had a surge or slight stumble under load, and an intermittent knock sensor code. I've put about 80,000 km on it since.

The original 2004 battery died about a year ago and I was broke so installed a freebie battery that I got from a buddy. It wasn't strong enough to crank his car in the winter but worked okay for mine. Replaced it with a new Delco battery about a month ago and the car has noticeably stronger acceleration, no stumbles and no knock sensor code since then.

I'm an ex GM Service Manager and I know the electrics are fairly voltage sensitive but I've never run into a new battery solving a stumble or surge.

I'm somewhat baffled, very happy, thought I'd share an unusual fix with my fellow inmates.

Cheers all
Peter