I picked this 97 vert up off a car lot guy took it for a test drive and broke top and car sat in back of lot for nearly a year. drove it home and ran great after 30 miles or so it started misfiring really low idle etc. I had a spare cover and coil pack so swaped it out and ran good. Idles perfect when cold but when it is hot it will drop to about 600 at idle and have a light surge to 650 or so and oil light comes on. Runs great every where but idle with no oil light. I think it is just idleing to low and not pumping enough oil cause of low rpms. Is there a way to turn up idle? Thank for any input

If the car idles nicely when cold but it idles roughly when warm, then your coolant temperature sensor (not thermostat) may be failing. That was the problem on my wife's 1996 2.4L convertible Cavalier. It idled fine when cold, but once it got warm, it idled roughly-- eventually getting to the point where it would stall.

It turned out that the coolant temperature sensor (not the thermostat) was operating improperly-- essentially telling the car's computer that the engine was colder than it really was. So the computer was always giving the engine a relatively rich fuel mixture for "cold" operation. That rich fuel mixture is fine when the engine is cold, but not once the engine is warm. (It's like the old days of pre-computerized, carbureted engines when you had to engage the "choke" when you first started an engine, but you had to kill the choke once the car warmed up.)

It may be worth emphasizing that I'm talking about the (cheap, cheap-to-replace) temperature sensor, NOT the (cheap, expensive-to-replace thermostat). It is also worth noting that the coolant temperature sensor didn't fail completely-- which would have made it very easy to diagnose. The sensor was just operating out-of-spec.

It may also be worth noting that my mechanic replaced an apparently-cracked MAP sensor vacuum line (which is VERY cheap and easy) when he replaced the coolant temperature sensor, but I think the real problem was the coolant temperature sensor. I wrote about it at the following link.

http://www.j-body.org/forums/read.php?f=11&i=159145&t=159145#159145