i just got my 89 and it idles around 1000 rpm. it does this regardless if its warm or cold. sometimes it goes to 12 but is pretty consistantly around 10-12. before doing anything i pulled the throttle back against the adjustment screw and it went to 6k and sat right there and idled nice. it appears the spring in the throttle body isnt strong enough to pull it all the way back to the screw.
i went to

https://www.corvetteforum.com/techti...D=55&TopicID=2

and followed that exactly and when i unplugged the IAC it idled at 6k. I finished adjusting the idle and screwed it in until it went all the way back against the screw and sat at 7k which i figured was a pretty good improvement. i turned off the car and replugged in the IAC and restarted it and it went back to its old ways. the problem is when it idles at 10k it feels like the trans is always engaged and im fighting it to brake.

i was thinking maybe try to replace the spring. i havent checked the vacuum system but the guy before me replaced all the vacuum lines and they appear to be good (when he replaced the injectors). another thought was a bad IAC that may be causing this. would it be bad to disconnect the IAC for now and drive like that?

also when i had the IAC disconnected if i turned the throttle back to try to get it to 4k it would stuble and sound like it was going to die. so the lowest i could get it to idle is 6k

i have included a picture of the injectors as they have no markings on them that i can see.

one last thing. as i am new to corvettes i was wondering if anyone could identify this piece in my trunk or tell me what its for.

 

it also has 126k if that matters at all

 

Those things in the trunk are where you put your top when you have it off the car.

 

it isn't a spring issue. it is because the throttle blades wear into the throttlebody cause the blades to always stay slightly open. a dremel can be used to smooth it out for better operation.

 

If it was ok when the IAC was disconected and acted up again I would be lookig at the IAC. Mechanical parts must be working properly. Wouldn't hurt to get some throttle body cleaner and clean the throttle body and some maf cleaner and clean maf. Check your IAC

 

Buy a generic throttle spring and temporarily mount it to see if it cures the problem. They are cheap, like me.

 

Make sure the rest of the cables are binding like the TV and cruise cables, they may be holding it open too.

Also, are you going by dash or plugged in for RPM? I thought my 87/90 was high, gauge said 1100, Datamaster tells me 660... (and it sounds right for 660)