1986 c4 corvette idle problem and transmission problem

[Grumpy]

i have a 1986 corvette it was to idle really weird it will runs between 500 to 700 rpms then drop to 100 rpms and want to die
and it has a knocking sound on the back right corner of the engine block and for the transmission it skipps third gear unless you put ur foot in it then it will shift down and as long as you keep foot in it as soon as you take your foot out it shifts into 4th and lugs the engine

step #1
what are the trouble codes?
you could and should check for a loose, or cracked flex-plate, or torque converter, a loose bell-housing and pull the valve cover and check for a valve train clearance or wear issue
http://garage.grumpysperformance.com/index.php?threads/c4-c5-corvette-trouble-codes.2697/
a logical step by step approach will lead you to the problem, youll be amazed at what youll learn reading links. use of a shop manual and multi meter can be very helpful

BTW it generally helps if you post the city and state your in,
as theres at least some chance a local member,
may want to stop by and help you diagnose,
and maybe help rectify the issue if your LOCAL

http://garage.grumpysperformance.com/index.php?threads/c3-c4-corvette-vacuum-diagrams.1773/

http://garage.grumpysperformance.co...ard-starting-tpi-crossfire-or-lt1-vette.1401/

http://garage.grumpysperformance.com/index.php?threads/adjusting-your-tps-and-iac.168/

http://garage.grumpysperformance.co...-system-trouble-shooting-flow-chart-info.596/

http://garage.grumpysperformance.co...too-common-questions-can-be-found-here.12892/

step #2 , get a shop manual, timing light, multi meter and vacuum and fuel pressure gauge because you darn sure want to verify the sensor functions