why am i losing fuel and engine running rough?

on 2002 Chevrolet Venture

my van is losing gas, dying when turning sharp and engine running rough. only 45mi hr up hill. needs tune up i know. just need to know where to start first. lots of miles on van

Asked by for the 2002 Chevrolet Venture
Your O2 sensor could be bad or going that way. It will make the vehicle run as if the timing is going out. You should smell strong gas fumes, usually when at the Mickey Dee's ;) Be sure to use the same octane rating or your onboard computer will be working overtime to adjust everything due to lower or higher ratings