My son bought his car, used 3 years ago, and it has been great up until two weeks ago. The car was stalling occasionally at stop lights, but would start right back up. Check engine light came on. We have had it in the shop several times and they have replaced several items, including sensors. We picked it up tonight. They said there is still a P1018 code pending, but the check engine light was not on. My son took a short drive and the check engine light is now back on. They told us to bring it back in if the light comes back on or if there any performance issues. Any suggestions?