My idle out of no wear will increase and wont come back down unless I shut the engine off and back on Dealer could not find problem I have changed idle control valve and throttle postion and still acts up Any one got a clue what to check for thanks

Without a code reader you are quessing. It could be your mass air flow sensor or even a vaccum leak. Follow those vaccum lines from the vaccum ball, especially those under the pllenumn. Good luck, coastal corvette.

My idle out of no wear will increase and wont come back down unless I shut the engine off and back on Dealer could not find problem I have changed idle control valve and throttle postion and still acts up Any one got a clue what to check for thanks
Had the same problem with my 92. It would fast idle after driving for awhile then shut off the motor and a fast idle until it decided different. I found it to be the computer. To see if it is the computer, do everything like normal, but take the computer out, close the hood to keep the heat in, put the computer in the frezer for about 15 minutes. Reinstall the computer, start then engine. If it starts normal, then the problem is the computer. Took me 6 months to get a good computer from Chevy. If you use the Checker computer it is a rebuilt unit.

Similar problem, turned out to be the computer also. It also affected my dash display and when it idled up it locked my mpg at 12.8. When it idled normally the display went back to normal and correct readings.

What yera car is this, and yes sounds like ECU.

most likely ECU as said. Grab one from a junkyard or corvette recycling, etc.