178,000 miles (best vehicle I have ever had) recently developed the following problem: starts great, cold idle fine, hot idle while in park the rpm will fluctuate from approx. 900 down to almost zero, "catches" itself as the idle slows and "corrects" back up to 900 rpm ........ this sequence repeats itself somewhat erratically over and over. Same thing while in gear but will quickly die.

Any help or insight would be greatly appreciated ........