I am now looking into the O2 sensor and temp sensor being a cause of idle surging. I know where the O2 sensor is, but not sure where the temp sensor is located.

Found old repair receipts and noticed that the idle surge was fixed a while back by replacing the wiring harness that had shorted at the EGR switch over valve (whatever and wherever that is). Also temp sensor was replaced a few months ago.

The idle surge problem started after the techs replaced a faulty water pump. Problem is, it was such an intermittent problem that they couldn't recreate the problem when I complained.

Are any of these components close to the water pump?

The temp sensor is located on the intake side of the head, under the air cleaner box toward the aft end of the head between the valve cover and intake mainfold. Has a single connector.