1997 Ford Thunderbird LX, 4.6L V8 and 197,000 miles (really : -).
While in park, idle seems to run at about 650-700 RPM and the engine runs smooth (having the a/c on or off doesn't matter).
While in gear, however, the idle slips down to about 500 RPM which causes the engine to run rough and vibrate (both physically as well as audibly). The actual idle can vary from this point as a low back up to normal from time to time. As in park, having the a/c on or off doesn't have any significant impact on the behavior.
Wondering about possible solutions. One suggestion is to throw a new idle air control valve at it, but before I start to spend money on random parts, wanted to try and get some concensus of possibilities.
Tuesday, October 23rd, 2007 AT 7:31 PM