2012 Kia Forte Runs great, but then sometime wont upshift
2012 KIA Forte, drove 400+ miles no issues, went to drive one morning,
topped out at around 45 MPH and wont change until for apx. 10 Minutes or
so, then drives fine. Had this issue now 4 or 5 times. Took to transmission
shop, it never acted up for them, and fluid looked good, said they could find
nothing wrong. Check engine light is on, codes at vacuum leak. Any ideas
what could be wrong or if this and the light are related? Could it be a speed
sensor?