Thanks for both replies.

Once when it was surging, I disconnected the three-wire connector on the IP, which dropped the rpm to low steady idle. I saw and felt nothing obviously wrong with wires and connector, don't know about internal. I plugged it back in, high (700 rpm) idle resumed, and so did the surging after a bit. Then the problem disappeared and did not reappear for a day or so.

It's raining heavily now, and I don't have garage space, so I'll try to find and check the sensor and wiring later. It's probably hidden well, and there is a fine 18-year old layer of oil from the PO who didn't clean the engine, and I've not had the courage so far, being a bit fearful of blasting connections loose or worse, especially doing so with no way to get to spare parts... Engine cleaning is on my list, just not at the top.

I'll grab a flash light and reading glasses to see which control model I have. Fortunately, I have removed the kick panels. Unfortunately, it's because the same PO had the sound shop put speakers on the panels, and they used fiberglass resin to hold the speaker housing... What a mess, but the control module is easily accessable, in fact my wife has to be careful not to kick it.

Thanks again, and I'll post results later.

Jim