Hopefully your problem is different then mine, but it sounds exactly how mine started....I developed a "ticking" that sounded definietly upper end but distinctly different from injectors (which should be audible at idle). I tried several things that you are mentioning, but after a couple months, the ticking is now over-powered by a distinct KNOCK (very audible at start-up, but not noticeable at hiher RPM's). I threw a cel code and took it the dealer to investigate. The cel is a bad pre-cat (this was the ticking, lighter noise...almost like marbles in a steel can...cat is fried). The cat is covered under warranty. The knock according to the dealer is a "lower failure" and they said they could rebuild it for $6k US or replace with a crate motor for $4500 US. I have absolutely NO loss of power or driveability and other than the noise would not know something was amiss. I've been driving it this way for 6 months now waiting for the fateful day (and fighting with ford). This occurred at 48k miles.....Since it hasn't failed in the last six months, I'm thinking maybe a wrist pin. Hope this isn't your problem!
Jeff
99 Tropic Green SVT Contour
