I was told my car has a vacuum leak, which is causing misfires, a noise under the hood, and a Check Engine light. Then, they said the intake manifold O rings need to be replaced.
Hi. This is a very common failure on vehicles like yours. So common, in fact, that there is a technical service bulletin (TSB) on it. The TSB is XT303-13 and it addressed the hissing sound from under the hood, as well as illuminated Check Engine Light with codes P0171 and P0174 stored. These codes indicate a lean condition, which is often the result of a vacuum leak. According to the TSB, the course for repair is to replace the o-ring on the intake manifold tuning valve (IMTV). The TSB says the o-ring is available separately, so there is no need to replace the entire valve.