I just bought an 03 GT. Recently I noticed a rattle in the engine when accelerating. It can't be heard while idling so I'm unsure exactly where it's coming from. It gets noticeably louder shifting into 3rd, but fades at higher speeds. There is also a slight loss of horsepower that comes and goes apparently at random while driving.
Previously, I noticed the engine would pulse when idling, wavering between 600-800rpms. After using a fuel system cleaner idle RPMs rest level at around 900. The rattling faded for about 100 miles but has since returned.
Can anyone tell me the problem and how to fix it? Temperatures have been between 30 and 40f here lately. I'm wondering if that may have something to do with it.
