Re: 1998 Ford 4.2L V6 idle issue

Thanks, I got a code reader for 21 bucks at Wallymart.
It fit on the plug under the dash, and with the eng running it indicated: P1537, P1538
Found this post online with some things to look into.
https://www.ford-trucks.com/forums/498733-codes-p1538-p1537-what-is-it.html
Meanwhile, I replaced the serpentine belt as the used car dealer had ordered it
and said I could have it.
I noticed a slight clicking coming from near the alternator area on the pass side
after the new belt was on and eng running. As the eng warmed up, the clicking seemed
to diminish, almost sounded like a bearing in the really early stages of EOL.
Previously I had noticed an RPM drop when idling at a light one time, seemed like
it was gonna stall but fully recovered quickly.
Last week the truck sat unstarted for 3 days, and it started up ok but
this RPM drop happened after only 15 seconds, then as before, it recovered fine
and I moved the truck into the workbay and did the serpentine belt job.
Didnt see the RPM drop with the new belt, but it only sat 2 days not 3.
Wondering if it could be the alternator bearing, or the idler or tension pulley
once in a while binding, slowing down to nearly a stall?
The dealer did say he replaced the tension pulley not long ago, and the old belt had signs
of fraying on the outer edges....?