I have a 2003 F-150 Supercrew (5.4L V-8) with 54,000 miles. I purchased it with 50,000 miles on it in February of 2005. Ever since I have owned it, whenever I accelerate hard, I hear a faint mechanical fluttering sound in the engine compartment. I used to hear this noise frequently with my old 1994 explorer, but the problem would go away if you ran 93 octane fuel in the vehicle. I used regular unleaded in the F-150 the first two tanks after purchase, and when I noticed the noise switched to premium 92/93 octane fuel; however, the noise did not go away.

Any suggestions on what normally causes this noise? Do I need to change the plugs, clean the fuel injectors, or is something else likely the culprit?

Thanks,
Brad Hatchett
2003 F-150 Supercrew Lariat
5.4L Triton V-8