Got a '99 with 65k on it, and just recently I noticed that sometimes, when holding the throttle steady, the engine will surge ever so slightly (<100rpm) as if the transmission is trying to upshift to go up a hill..usually its level ground or a very slight grade. At first I thought it was cruise control, because that's when I first noticed it at 75mph. Now it'll hit around 1500rpm no matter the speed. If I give it just the slightest variation in throttle it'll either slack off or shift up, depending which direction my foot chooses to go. Think its some wacky sensor deal in the engine, or is my tranny packing its bags to go south?
Unrelated note, I'm about a quarter inch low on coolant every oil change or two. There's no leak in the system (at least the perimeter) and I'm sure by now the infamous gaskets are trying to go on me. I don't smell funky exhaust and I don't see anything out of the ordinary in my oil. Got an opinion on this?