Thunderbird May 1994 T-Bird runs good but it runs at a high idle .As I drive the car the RPM gauge will go high or drop completely and then pick back up. I have checked all the vaccum lines and wasn't sure what else to check.

IAC valvle located on top of throttle body. Before replacing get the calibration code off the sticker on the door jamb, or else Ford will sell you the wrong one and maybe the parts store. Ive run into that with mine because it cause mine to idle high at red light and car didint want to brake proeprly, kept pulling.

Also clean out passage way with some strong carb/brake cleaner to remove any debris or trapped sludge that gets sucked back into system by vacuum hose from valve cover.

IAC valve makes rpm high when having much dust in it.
Replacement costed me $200.

Dear Customer,

check engine oil level

If long times happen than change your oil first than try to shift your car's transmision at right speed cause some cars having low bhp according to weight so,its may haapen also at slop at mountain ar canyon driving,

take it easy,do with care to car,

THNX